15
Life Cycle Cost and Benefit Analysis

The essence of sustainable design is to optimally balance capital, and operation and maintenance costs.

15.1 Principle

To reduce life cycle cost and maximize benefit over the life expectancy of an EEIS, standardized and modularized technologies play a key role in all the environmental engineering infrastructure (EEI) systems. Up‐front capital costs, operating costs, and total expected present value costs will be significantly reduced using modular components. For decentralized WRRF or even centralized WRRFs, emerging innovative technologies in anaerobic digestion, biomass conversion, and nutrient recovery technologies might significantly increase system reliability and resiliency. For example, molten salt fuel cell (MSFC) technologies could generate hydrogen, heat, and electricity without any emission while reducing the physical and environmental footprint of a WRRF. A standardized modular system could also be more resilient to influent variation of flow and wastewater quality by employing different modules. For remote areas and external acute stressors such as hurricanes and earthquake, modular system could be readily deployed. Furthermore, the economies of scale of large centralized wastewater treatment plant (WWTP) could diminish if it were compared with an integrated standardized modularized system. For SEE, standards on modular engineering design are extremely important. The following is a table of Principle 12.

15.2 Challenges and Opportunities

Traditional environmental engineering (EE) evoluted from civil engineering and inherits tank design as huge inefficient treatment processes. SEE attempts to change the historical mindset of traditional EE to embrace new challenges and opportunities under climate change. Since unit processes in the past are not modular, no uniform industrial standards were established. On other hand, international standards and protocol of telecommunication device using the protocol of Internet of things (IoT) made it possible for all the electronic devices to be connected. In developing countries such as China, WWTPs mostly use activated sludge and are becoming major pollution sources if sludge was not properly disposed due to high operations and maintenance (O&M) costs. After energy‐intensive activated sludge treatment, huge quantity of sludge is generated. Its treatment became a major financial burden for local water utilities. In addition, WTPs and WWTPs in China were designed without consideration of life cycle assessment on environments as well as footprints. Although 4800 WWTPs in China are relative new, these plants are not efficient because all of them were designed by using activated sludge with huge aeration tanks and produce large amount of sludge. Most of these WWTPs do not have anaerobic digesters to generate biogas to power the plants, and retrofitting these WWTPs are the major challenges in China and other developing countries. At the same time, the developed countries also need upgrade or retrofit current WTPs and WWTPs to extend their serve life. When the plants approach to its design life, effluent quality deteriorated so much that it is either beyond repair or out of capacity. For example, the City of Opa‐locka WTP reached its design life of 50 years. The water quality deteriorated so much that Florida Department of Environmental Protection denied its water withdrawal permit. The WTP was shut down in 1980. In Miami‐Dade County, the WWTP could not satisfy peak flow capacity, and the US Environmental Protection Agency (EPA) fined two million dollars for violation of overflow rules and imposed three concert decrees to the Miami-Dade county. The county has to sell 13.6 billion dollar bond to retrofit its aging WWTP and sewage and pump system. Yet, if local governmental agencies are not up to modern design innovation, sustainability issue will come back again and cause financial difficulty of the local governments. For these reasons, life cycle cost and benefit analysis becomes crucial.

Every four years, the US EPA prepares a report to Congress, based on a survey of states, on the unfunded capital costs for projects to address water quality or water quality‐related health problems due to combined sewer overflows. As of 2008, states had identified the need for $63.6 billion to address combined sewer system overflows and $42.3 billion for stormwater management. One approach to address combined sewer overflows is to replace a single combined sewer system with separate storm and sanitary sewer systems. Directing storm sewer flows to waterways and sanitary sewer flows to treatment plants can ensure that flow rate to WWTPs does not exceed capacity during periods of heavy rain or snowmelt. However, system separation is expensive and leaves untreated stormwater flowing directly to rivers, lakes, and estuaries. Another approach is to construct underground facilities that can hold excess wastewater from combined sewer systems until WWTPs has the capacity to handle it.

With different SEE design alternatives, life cycle cost and benefit analysis is one of the most important ways in selecting final design alternative. While monetary damage by sewer overflow and stormwater pollution of rivers may be difficult to quantify, environmental tax to be imposed by the Chinese Ministry of Environmental Protection (CMEP) provides easy way to quantify the monetary benefits of SEE design alternatives. Following are list of environmental tax of major air, water, solid wastes, and noise pollutants to be effective on 1 January 2018 (Table 15.1).

Table 15.1 Environmental tax items and rates by CMEP.

Taxable items Tax unit Amount taxed ($)
Air pollutants Per pollution equivalent 0.17–1.71
Water pollutants Per pollution equivalent 0.20–2.00
Solid waste Coal gangue Per ton 0.71
Tailings Per ton 2.14
Hazardous waste Per ton 142.86
Other solid wastes (including semisolid and liquid waste) Per ton 3.57
Noise pollution Industrial noise 1–3 dB above standard Per month 50.00
4–6 dB above the standard Per month 100.00
7–9 dB above the standard Per month 200.00
10–12 dB above the standard Per month 400.00
13–15 dB above the standard Per month 800.00
16 dB above the standard Per month 1600.00

Water pollutants are further divided as class I and II as follows (Tables 15.2, 15.3, 15.4, 15.5, and 15.6).

Table 15.2 Class I water pollutants pollution equivalent values.

Pollutants Pollution equivalent values (kg)
1. Total mercury 0.000 5
2. Total cadmium 0.005
3. Total chromium 0.04
4. Chromium(VI) 0.02
5. Total arsenic 0.02
6. Total lead 0.025
7. Total nickel 0.025
8. Benzo(a)pyrene 0.000 000 3
9. Total beryllium 0.01
10. Total silver 0.02

Table 15.3 Class II water pollutants pollution equivalent values.

Pollutants Pollution equivalent values (kg)
11. Suspended solids (SS) 4
12. Biochemical oxygen demand (BOD5) 0.5
13. Chemical oxygen demand (COD) 1
14. Total organic carbon (TOC) 0.49
15. Petroleum and derivatives 0.1
16. Animal and vegetable oils 0.16
17. Volatile phenols 0.08
18. Total cyanides 0.05
19. Sulfides 0.125
20. Ammonia nitrogen 0.8
21. Fluorides 0.5
22. Formaldehyde 0.125
23. Aniline 0.2
24. Nitrobenzene 0.2
25. Linear alkylbenzene sulfonate (LAS) 0.2
26. Total copper 0.1
27. Total zinc 0.2
28. Total manganese 0.2
29. Color developing reagent (CD‐2) 0.2
30. Total phosphorus 0.25
31. Elemental phosphorus (measured in P) 0.05
32. Organophosphorus pesticides (measured in P) 0.05
33. Dimethoate 0.05
34. Parathion methyl 0.05
35. Malathion 0.05
36. Parathion 0.05
37. Pentachlorophenol sodium pentachlorophenate (in terms of PCP) 0.25
38. Chloroform 0.04
39. Adsorbable organic halide (AOX) (measured in Cl) 0.25
40. Carbon tetrachloride 0.04
41. Trichloroethylene 0.04
42. Tetrachloroethylene 0.04
43. Benzene 0.02
44. Methylbenzene 0.02
45. Ethylbenzene 0.02
46. ortho‐Xylene 0.02
47. para‐Xylene 0.02
48. meta‐Xylene 0.02
49. Chlorobenzene 0.02
50. ortho‐Dichlorobenzene 0.02
51. p‐Dichlorobenzene 0.02
52. p‐Nitrochlorobenzene 0.02
53. 2,4‐Dinitrochlorobenzene 0.02
54. Phenol 0.02
55. m‐Cresol 0.02
56. 2,4‐Dichlorophenol 0.02
57. 2,4,6‐Trichlorophenol 0.02
58. Fat‐dibutyl phthalate 0.02
59. Dioctyl phthalate 0.02
60. Acrylonitrile 0.125
61. Total selenium 0.02

Note:

1) The basis for the classification of class I and II pollutants is the “Integrated Wastewater Discharge Standard” (GB8978‐1996).

2) Only one item is levied environmental protection taxes among the chemical oxygen demand (COD), the biochemical oxygen demand (BOD5), and the total organic carbon (TOC) from a single discharge outlet.

Table 15.4 Pollution equivalent values for pH values, color, coliform group numbers, and the amount of residual chlorine.

Pollutants Pollution equivalent values Unit
1. pH values 0–1, 13–14 0.06 Tons of sewage
1–2, 12–13 0.125 Tons of sewage
2–3, 11–12 0.25 Tons of sewage
3–4, 10–11 0.5 Tons of sewage
4–5, 9–10 1 Tons of sewage
5–6 5 Tons of sewage
2. Color 5 Tons of water times
3. Coliform group numbers (above standards) 3.3 Tons of sewage
4. Amount of residual chlorine (hospital wastewater disinfected with chlorine) 3.3 Tons of sewage

Note:

1) Taxes are levied either on coliform group numbers or on the amount of residual chlorine.

2) pH 5–6 refers to [a pH value] greater than or equal to 5 and less than 6, pH 9–10 refers to [a pH value] greater than 9 and less than or equal to 10, and so forth.

Table 15.5 Pollution equivalent values for livestock husbandry, small business, and the tertiary industry.

Type Pollution equivalent values Unit
Livestock farms 1. Cattle 0.1 Head
2. Pigs 1 Head
3. Chicken, ducks, and other poultry 30 Birds
4. Small businesses 1.8 Tons of sewage
5. Catering, entertainment, and service industries 0.5 Tons of sewage
6. Hospitals Disinfected 0.14 Beds
2.8 Tons of sewage
Not disinfected 0.07 Beds
1.4 Tons of sewage

Note:

1) This chart only applies to the calculation of pollution equivalent numbers of small polluters such as livestock husbandry industry, small businesses, and the tertiary industry for which actual monitoring or materials accounting cannot be conducted.

2) Tax is only levied against livestock breeding farms with stock of more than 50 heads of cattle, 500 pigs, or 5000 chicken or ducks.

3) Where there are more than 20 beds in a hospital, follow this chart to calculate the pollution equivalent values.

Table 15.6 Atmospheric pollutant equivalent values.

Pollutants Pollution equivalent values (kg)
1. Sulfur dioxide 0.95
2. Nitrogen oxides 0.95
3. Carbon monoxide 16.7
4. Chlorine gas 0.34
5. Hydrogen chloride 10.75
6. Fluoride 0.87
7. Hydrogen cyanide 0.005
8. Sulfuric acid mist 0.6
9. Chromic acid mist 0.0007
10. Mercury and its compounds 0.0001
11. The general dust 4
12. Asbestos dust 0.53
13. Glass cotton dust 2.13
14. Carbon black dust 0.59
15. Lead and its compounds 0.02
16. Cadmium and its compounds 0.03
17. Beryllium and its compounds 0.0004
18. Nickel and its compounds 0.13
19. Tin and its compounds 0.27
20. Dust 2.18
21. Benzene 0.05
22. Toluene 0.18
23. p‐Xylene 0.27
24. Benzo(a)pyrene 0.000002
25. Formaldehyde 0.09
26. Acetaldehyde 0.45
27. Acrolein 0.06
28. Methanol 0.67
29. Phenol 0.35
30. Asphalt smoke 0.19
31. Aniline 0.21
32. Chlorobenzene 0.72
33. Nitrobenzene 0.17
34. Acrylonitrile 0.22
35. Chlorethylene 0.55
36. Phosgene 0.04
37. hydrogen sulfide 0.29
38. Ammonium 9.09
39. Trimethylamine 0.32
40. Methyl mercaptan 0.04
41. Methyl sulfide 0.28
42. Dimethyl disulfide 0.28
43. Styrene 25
44. carbon disulfide 20

15.3 Optimum Pipe Size

Optimal pipe size should be determined by the capital cost and its O&M costs during its life cycle. From a shortsighted point of view, the best pipe size is clearly the littlest size that will suit the current application. From a sensible stance, ideal channel size can have numerous implications with legitimate thought of the application. Ideal can mean monetarily productive over the life of a framework. Therefore, optimal pipe size can minimize cost of capital and operation over the lifetime of a pipe.

15.4 Advanced Oxidation Process Costs

15.4.1 UV Disinfection

The US EPA (2005) provides the following cost analysis of ultraviolet (UV) disinfection systems: For flow rate less than 1 MGD, low‐pressure (LP) UV lamp is usually used. For all systems, when flow rate is greater than 1 MGD, cost estimates reflect either LP or medium‐pressure (MP) lamp systems. Equipment, replacement parts, labor, and power requirements are usually based upon manufacturers’ information. Other associated costs by UV equipment costs represent only a portion of the total process costs. Additional process costs include instrumentation and controls, interstage pumping, piping and valves, and housing. For small systems (flows <1.0 MGD), additional process costs are estimated by using the capital cost multiplier as shown in Table 15.10. Indirect capital costs (for both large and small systems) include pilot testing, training, and spare parts. Pilot testing cost assumptions for UV are presented in Table 15.10.

Table 15.10 Capital cost multiplier.

Design flows (MGD) Capital cost multiplier
<0.1–1.2 1 000
2–17 5 000
17–76 10 000
>76 200 000

Capital cost multipliers used for UV disinfection differ from those recommended by National Drinking Water Advisory Council (NDWAC). For flows less than 1 MGD, the capital cost multiplier is 1.2. For flows greater than or equal to 1 MGD, the capital cost multiplier is 1.36 for systems using a dose of 40 mJ/cm2 and 1.76 for a dose of 200 mJ/cm2. Systems less than 1 MGD require a smaller capital cost multiplier than other treatment technologies because small UV systems do not need significant area (i.e. new building not needed), equipment installation is not complex, and plant modifications are minor compared with other technologies. The capital cost multiplier of 1.36 used for 40 mJ/cm2 systems is a revised multiplier based on actual data from facilities. The lower‐cost multiplier was used because lower installation costs and less site work are necessary compared with other treatment technologies.

Indirect capital costs for systems using a dose of 40 mJ/cm2, pilot testing, operator training, housing, and a spare parts inventory are included as indirect capital costs. Pilot testing was assumed to be $1 000 for systems with a design flow of less than 2 MGD, $5 000 from 2 to 10 MGD, $10 000 for 10–25 MGD, and $200 000 for systems with a design flow greater than 25 MGD. Operator training was assumed to be $1 000 for small systems and ranges from $3 000 to $25 000 for larger systems. Housing costs were based on the estimated UV system footprint size multiplied by a median housing unit costs of $150/ft2 based on actual UV costs. Footprint sizes ranged from 335 to 22 000 ft2. Also, based on data reported from 18 actual UV facilities, it was assumed that 39% of facilities would not require an additional building; therefore the housing costs were reduced by this percentage to reflect a national average cost. The spare parts inventory costs were based on a 10% backup of system equipment including lamps, sleeves, and sensors, with the exception of ballasts and ultraviolet transmittance (UVT) monitors that were based on a 5% and one unit backup of system equipment, respectively.

The O&M costs reflect labor hours, replacement parts, and lamp operating information provided by the manufacturer. The number of lamps, sensors, and ballasts is different, depending on the different manufacturer. Costs for replacement parts for each manufacturer were based on the following replacement intervals:

  1. LP lamps replaced annually.
  2. MP lamps replaced every 6 months.
  3. Sleeves replaced every 8 years.
  4. Intensity sensors and reference sensors replaced every 5 years.
  5. Ballasts and UVT monitors replaced every 10 years.

For systems treating less than 2 MGD, 1 h of labor per month plus an additional 2 h per lamp replacement was assumed. For systems treating more than 2 MGD, labor hours were estimated by manufacturers for the following tasks: daily operation, lamp replacement (annually for LP lamps and every 6 months for MP lamps), quarterly sensor calibration, and cleaning once per month for UV systems that do not use automatic cleaning. Labor costs were derived from the labor hours estimate and assumed labor rate. Table 15.11 represents the US EPA’s estimate of UV disinfection cost.

Table 15.11 UV disinfection cost summary (40 mJ/cm2 without UPS) (EPA 2005).

Design flow (MGD) 0.007 0.022 0.037 0.091 0.18 0.27 0.36 0.68 1
Average flow (MGD) 0.0015 0.0054 0.0095 0.025 0.054 0.084 0.11 0.23 0.35
Capital cost summary
Total capital cost 10 195 13 034 15 834 25 596 40 597 54 386 66 790 99 661 310 154
Indirect capital costs 3 686 3 704 3 722 3 794 3 934 4 102 4 296 5 200 6 206
Training 1 000 1 000 1 000 1 000 1 000 1 000 1 000 1 000 1 000
Treatability testing 1 000 1 000 1 000 1 000 1 000 1 000 1 000 1 000 1 000
Spare parts 1 686 1 704 1 722 1 794 1 934 2 102 2 296 3 200 4 206
Direct capital cost1 6 509 9 330 12 112 21 802 36 662 50 284 62 493 94 461 303 947
Subtotal process cost 5 424 7 775 10 094 18 168 30 552 41 903 52 078 78 717 223 491
I&C (incl. HVAC) — — — — — — — — 40 000
Pipes and valves — — — — — — — — 17 717
Adjusted pumping — — — — — — — — 1 564
Adjusted housing — — — — — — — — 20 210
UV reactors 5 424 7 775 10 094 18 168 30 552 41 903 52 078 78 717 128 000
Electrical — — — — — — — — 16 000
Annual O&M cost summary
Total O&M cost 3 350 3 380 3 769 4 549 4 736 6 115 6 493 8 152 9 016
Replacement parts 3 000 3 000 3 377 4 000 4 000 5 200 5 400 6 400 6 800
Power/electricity 50 80 91 180 320 420 524 960 1 400
Labor $ 300 300 300 369 416 495 569 792 816
UV (dose = 40 mJ/cm2, UV254 = 0.05, turbidity = 0.1 NTU, Alk = 60 mg/l, hardness = 100 mg/l) 737.1 215.9 139.4 68.7 37.9 31.9 27.4 17.7 23.4
UV (dose = 200 mJ/cm2, UV254 = 0.05, turbidity = 0.1 NTU, Alk = 60 mg/l, hardness = 100 mg/l) 1 870.7 562.2 368.8 190.9 117.8 97.7 84.9 58.6 64.3
UV with UPS (dose = 40 mJ/cm2, UV254 = 0.05, turbidity = 0.1 NTU, Alk = 60 mg/l, hardness = 100 mg/l) 129.7 45.9 31.6 19.3 14.2 12.3 11.5 8.4 16.7
UV with UPS (dose = 200 mJ/cm2, UV254 = 0.05, turbidity = 0.1 NTU, Alk = 60 mg/l, hardness = 100 mg/l) 2 140.2 640.5 413.8 208.9 126.7 103.8 89.9 61.5 67.6

The US EPA reported a detail cost of treating methyl tertiary-butyl ether (MTBE) using granular activated carbon (GAC) and advanced oxidation process (AOP). Relevant assumptions and costs for these polishing systems using Calgon Filtrasorb 600 carbon are listed in Tables 15.12 and 15.13. Costs generally are between $0.03 and $3.00 per 1000 l ($0.10–$10.00 per 1000 gal). Factors that influence the cost to implementing UV/oxidation include:

  1. Types and concentration of contaminants (as they affect oxidizer selection, oxidizer dosage, UV light intensity, and treatment time).
  2. Degree of contaminant destruction required.
  3. Desired water flow rates.
  4. Requirements for pretreatment and/or posttreatment.

Table 15.12 Cost of hydrogen peroxide removal.

H2O2 treatment systems (centaur carbon)
Flow rate (gal/min) Capital costs ($) Annual O&M costs ($) Total amortized operating costs ($/1000 gal)
60 18 000 39 000 1.27
600 89 000 44 000 0.60
6000 667 000 194 000 0.10

Table 15.13 Cost of oxidation by‐product removal.

Treatment for TBA, TBF, acetone, and other by‐products (Bio‐GAC)
Flow rate (gal/min) Capital costs ($) Annual O&M costs ($) Total amortized operating costs ($/1000 gal)
60 16 700 42 200 1.38
600 67 800 42 700 0.15
6000 667 000 204 800 0.08

Note:

60 gpm systems consist of one 500‐lb GAC vessel.

600 gpm systems consist of one 5000‐lb GAC vessel.

6000 gpm systems consist of ten 5000‐lb GAC vessels.

O&M costs include carbon replacement, equipment, analytical sampling, oversight during change‐outs, and general system O&M.

Capital costs include pining, valves, electrical (30%), site work (10%), contractor O&P (15%), engineering (15%), and contingency (20%).

Tables 15.14 and 15.15 provide a sample calculation of total capital costs, total annual costs, and unit treatment costs of H2O2/O3 system for MTBE removal. As these tables indicate, the capital costs provided by the vendors were the bases for estimating the complete installed system costs. Piping, valves, and electrical work were estimated at 30% of the system equipment costs. Site work was estimated at 10% of equipment costs, engineering was estimated at 15% of equipment costs, and contractor O&M was estimated at 15% of equipment costs. A contingency of 20% of the total costs was then added.

Table 15.14 Costs of H2O2 /O3 system for MTBE removal (Applied Process Technology, Inc).

Items Cost ($)
Advanced oxidation unita 750 000
Piping, valves, electrical (30%) 225 000
Site work (10%) 75 000
Contractor O&P (15%) 157 500
Engineering (15%) 181 125
Subtotal 1 388 625
Contingency (20%) 277 725
Total capital 1 666 400
Amortized capital 134 290
Annual O&M 129 692
Total annual cost 263 981
Total cost/1000 gal treated 0.84

a Cost of oxidation unit from vendor.

Table 15.15 Summary of annual O&M costs of H2O2 /O3 system for MTBE removal.

Summary of annual O&M costsa
Item Unit Quantity Unit cost ($) Cost ($)
Replacement partsb Lump sum 1 11 250 11 250
Laborc Hour 724 80 57 920
Analytical costsd Sample 208 200 41 600
Chemical costse $/1000 gal 315 360 0.03 9 461
Power ($0.08/kWh)f kWh 118 263 0.08 9 461
Annual O&M 129 692

Note:

System parameters: 600 gpm.

200 µg/l influent MTBE concentration.

20 µg/l effluent MTBE concentration.

a Amortization based on 30 year period at 7% discount rate.

b Replacement is based on vendor’s estimate of 1.5% capital cost.

c Breakdowns of labor costs are based on a rate of $80/h.

d Sampling conducted weekly at four locations.

e Chemical costs based on dosages and prices estimated by vendor.

f Power is based on consumption estimates provided by vendor, priced at $0.08/kWh.

Table 15.16 presents a summary of the capital costs for three AOP technologies evaluated under the scenarios identified. The capital costs include the complete treatment system and installation.

Table 15.16 Capital costs of AOPs.

Flow (gpm) Influent (µg/l) Effluent (µg/l) Removal efficiency (%) Calgon Carbon Corporation ($) Applied Process Technology, Inc. ($) Oxidation Systems, Inc. ($) Hydroxyl Systems, Inc. ($)
60 20 5 75.00 177 700 444 400 134 400 277 700
60 20 0.5 97.50 188 900 444 400 242 800 426 600
60 200 20 90.00 177 700 444 400 156 600 426 600
60 200 5 97.50 188 900 444 400 242 800 439 900
60 200 0.5 99.75 188 900 533 200 260 000 586 600
60 2000 20 99.00 188 900 533 200 260 000 586 600
60 2000 5 99.75 188 900 533 200 260 000 517 700
60 2000 0.5 99.98 266 600 622 100 260 000 691 000
600 20 5 75.00 266 600 1 666 400 356 600 1 142 000
600 20 0.5 97.50 488 800 1 777 400 461 200 1 344 200
600 200 20 90.00 337 700 1 666 400 356 600 1 344 200
600 200 5 97.50 488 800 1 777 400 461 200 1 730 800
600 200 0.5 99.75 695 400 1 777 400 792 100 2 035 200
600 2000 20 99.00 695 400 1 777 400 482 100 2 035 200
600 2000 5 99.75 811 000 1 888 500 482 100 2 628 400
600 2000 0.5 99.98 1 299 800 1 888 500 482 100 3 092 800
6000 20 5 75.00 999 800 7 998 500 1 446 400 9 711 500
6000 20 0.5 97.50 2 666 200 8 887 200 4 151 000 9 711 500
6000 200 20 90.00 1 666 400 7 998 500 3 209 400 11 426 700
6000 200 5 97.50 3 332 700 8 887 200 4 151 000 14 703 900
6000 200 0.5 99.75 4 221 400 8 887 200 4 339 200 17 298 900
6000 2000 20 99.00 4 999 000 8 887 200 4 339 200 17 298 900
6000 2000 5 99.75 6 665 400 8 887 200 4 339 200 22 344 600
6000 2000 0.5 99.98 9 998 100 9 775 900 4 339 200 26 288 300

Note:

Capital costs include equipment costs (provided by vendor), piping, valves, electrical (30%), site work (10%), contractor O&P (15%), engineering (15%), and contingency (20%).

Costs exclude polishing treatment. Refer to Tables 15.12 and 15.13 for additional treatment costs.

Table 15.17 presents a summary of the annual O&M costs for the three AOP technologies evaluated under the same scenarios described above. The O&M costs consist of replacement parts, labor, analytical, chemical, and electrical costs. The replacement part costs are based on vendor estimates and include replacement parts, such as UV lamps, and spare parts. The labor costs include labor for sampling of water, system operation, and general maintenance for the specific type of AOP. The maintenance and sampling labor rate used was $80/h. Analytical costs are based on weekly sampling of the influent and the effluent from each reactor and are estimated at $200 per sample. Chemical costs include H2O2, O3, and TiO2 as they apply to the technology and were provided by the vendor (both dosage and costs). The electrical cost was based on power consumption and was estimated by the vendors based on $0.08/kWh. Amortized annual capital costs and annual O&M costs were combined to determine the total amortized operating costs for each system per 1000 gal of treated water as presented in Table 15.18. The equipment was amortized at a discount rate of 7% over a 30‐year period.

Table 15.17 Annual O&M costs of AOPs.

Flow (gpm) Influent (µg/l) Effluent (µg/l) Removal efficiency (%) Calgon Carbon Corporation ($) Applied Process Technology, Inc. ($) Oxidation Systems, Inc. ($) Hydroxyl Systems, Inc. ($)
60 20 5 75.00 54 400 47 162 60 200 74 831
60 20 0.5 97.50 63 700 48 800 62 900 78 531
60 200 20 90.00 58 900 47 700 60 400 79 131
60 200 5 97.50 63 700 48 800 62 900 80 131
60 200 0.5 99.75 70 600 50 900 66 300 90 231
60 2000 20 99.00 81 600 60 800 71 700 100 131
60 2000 5 99.75 94 200 61 500 74 600 95 731
60 2000 0.5 99.98 108 000 63 900 75 200 107 431
600 20 5 75.00 157 800 123 400 167 700 265 300
600 20 0.5 97.50 248 300 139 900 174 500 277 900
600 200 20 90.00 198 200 129 800 167 700 280 100
600 200 5 97.50 264 000 139 900 174 500 330 500
600 200 0.5 99.75 343 500 155 700 208 100 349 500
600 2000 20 99.00 422 000 193 300 202 700 373 400
600 2000 5 99.75 487 700 203 500 233 100 452 200
600 2000 0.5 99.98 551 500 222 500 239 400 483 700
6000 20 5 75.00 930 600 464 500 1 101 900 2 389 400
6000 20 0.5 97.50 1 429 600 628 100 1 177 200 2 515 500
6000 200 20 90.00 1 190 400 527 500 1 109 800 2 535 500
6000 200 5 97.50 1 631 800 628 100 1 177 200 3 103 200
6000 200 0.5 99.75 1 989 000 785 900 1 512 900 3 197 800
6000 2000 20 99.00 1 657 400 1 061 700 1 359 300 3 431 800
6000 2000 5 99.75 3 386 100 1 156 400 1 662 700 4 346 400
6000 2000 0.5 99.98 4 210 900 1 351 600 1 725 800 4 504 000

Note:

O&M costs include replacement parts (based on vendor’s estimate), labor costs at $80/h, analytical costs for sampling conducted weekly at $200 per sample, chemical costs based on dose and price estimated by vendor, and power based on consumption estimates provided by vendor, priced at $0.08/kWh.

Costs exclude polishing treatment. Refer to Tables 15.12 and 15.13 for additional treatment costs.

Table 15.18 Total amortized operating costs (per 1000 gal treated) for AOPs.

Flow (gpm) Influent (µg/l) Effluent (µg/l) Removal efficiency (%) Calgon Carbon Corporation ($) Applied Process Technology, Inc. ($) Oxidation Systems, Inc. ($) Hydroxyl Systems, Inc. ($)
60 20 5 75.00 2.18 2.63 2.25 3.08
60 20 0.5 97.50 2.50 2.68 2.61 3.58
60 200 20 90.00 2.32 2.65 2.32 3.60
60 200 5 97.50 2.50 2.68 2.61 3.67
60 200 0.5 99.75 2.72 2.98 2.77 4.36
60 2000 20 99.00 3.07 3.29 2.94 4.67
60 2000 5 99.75 3.47 3.31 3.03 4.36
60 2000 0.5 99.98 4.11 3.62 3.05 5.17
600 20 5 75.00 0.57 0.82 0.62 1.13
600 20 0.5 97.50 0.91 0.90 0.67 1.22
600 200 20 90.00 0.71 0.84 0.62 1.23
600 200 5 97.50 0.96 0.90 0.67 1.49
600 200 0.5 99.75 1.27 0.95 0.86 1.63
600 2000 20 99.00 1.52 1.07 0.77 1.70
600 2000 5 99.75 1.75 1.13 0.86 2.11
600 2000 0.5 99.98 2.08 1.19 0.88 2.32
6000 20 5 75.00 0.32 0.35 0.39 1.01
6000 20 0.5 97.50 0.52 0.43 0.48 1.05
6000 200 20 90.00 0.42 0.37 0.43 1.10
6000 200 5 97.50 0.60 0.43 0.48 1.36
6000 200 0.5 99.75 0.74 0.48 0.59 1.46
6000 2000 20 99.00 0.65 0.56 0.54 1.53
6000 2000 5 99.75 1.24 0.59 0.64 1.95
6000 2000 0.5 99.98 1.59 0.68 0.66 2.10

Note: Amortized at 7% over 30 years.

The cost estimates provided by Calgon Carbon Corporation were for their H2O2/MP‐UV system. The cost per 1000 gal of treated water ranged from $0.32 (6000 gpm, 20 µg/l) to $4.11 (60 gpm, 2000 µg/l). Calgon had among the lowest capital costs with relative high O&M costs. The costs prepared by Calgon were based on meeting the specified effluent concentration of MTBE. However, by‐products produced as a result of the oxidation process would require further treatment to meet drinking water standards. Calgon provided the most complete analyses on by‐product formations and quantified by‐product formation based on the data extrapolated from an actual study and provided estimates for the 600 gpm scenario. In addition, Calgon calculated the hydrogen peroxide residual remaining in the treated water. Because these concentrations are high (>10 mg/l), an additional treatment step will be required for H2O2 removal. Calgon recommended using Centaur carbon for removal of the excess H2O2 and a biologically activated carbon system for removal of acetone, formaldehyde, and other acids prior to distribution of the treated drinking water.

15.5 Recovery of N and P

Phosphorus (P) as one of the essential elements of life could be depleted in the next hundred years if it is not sustainably managed because P can neither be produced synthetically nor substituted by any other elements (Kabbe, 2015). In addition, it is unevenly distributed on earth. For example, Morocco has about 75% of the world P rock deposit, while the United States and China have another 5% of the world reserve each. The rest of the world has the rest of 15%. As a result, the recovery of phosphorus from sludge or wastewater is the third important priority after water and energy recoveries. Up to 90% of the phosphorus entering the WWTP is transferred into the sewage sludge (Pinnekamp et al., 2013). Therefore, the recovery of phosphorus from the sewage sludge line offers a higher potential of phosphorus recovery in comparison with a recovery process from the effluent of the WWTP. To effectively quantify the yield efficiency, following definitions are used.

15.5.1 Yield Coefficients

The overall phosphorus yield is the phosphorus mass flow recovered in the final recycling product divided by the total phosphorus mass flow that enters the WWTP. Therefore this yield shows which proportion of the total phosphorus content available in the wastewater can be recovered with the corresponding process:

(15.1)images

The sludge specific phosphorus release yield is the phosphorus mass flow in the sludge liquor phase (as dissolved PO4–P) divided by the mass flow of phosphorus in the digested sludge. Therefore this yield shows which proportion of the phosphorus available in the digested sludge can be dissolved:

(15.2)images

The sludge specific phosphorus yield is the phosphorus mass flow recovered in the final recycling product divided by the total mass flow of phosphorus in the digested sludge. Therefore this yield shows which proportion of the phosphorus available in the digested sludge can be recovered with the corresponding process:

(15.3)images

The liquor specific phosphorus yield is the phosphorus mass flow recovered in the final recycling product divided by the total mass flow of phosphorus in the sludge liquor phase. Therefore this yield shows which proportion of the phosphorus available in the sludge liquor phase can be recovered with the corresponding process:

(15.4)images

Almost all processes developed for phosphorus recovery focus on this fraction of the phosphorus originally contained in the raw wastewater. Elimination of dissolved phosphate from wastewater and the transfer into sewage sludge are at least partly taking place by bacterial growth (38–45%) (Pinnekamp et al., 2007). The phosphorus is used by the microorganisms in the activated sludge as nutrient and included into the biomass. The phosphorus needs to be extracted in dissolved form out of the sludge matrix to produce mineral fertilizers. During digestion of the sludge, its biomass is degraded, and therefore biologically bound phosphorus released into the liquid phase of the sludge is water‐soluble orthophosphate. This is especially the case for phosphorus taken up by phosphorus‐accumulating bacteria due to anaerobic conditions during digestion, which lead to an enhanced release of phosphorus from the bacteria. The amount of phosphorus dissolved after the digestion is estimated to account for up to 23% of the phosphorus contained originally in the wastewater (Cullen et al., 2013).

Four processes have been developed to recover phosphorus in a European Union project. One process applies a reactor in which the crystallization of a mineral phosphorus product occurs directly in the sludge (AirPrex®). The other three processes are applied on the process water after sludge dewatering by mechanical solid–liquid separation like centrifugation (Struvia process, Crystalactor, Pearl® process). These three processes are also applicable to industrial wastewater containing significant concentration of dissolved orthophosphate. The AirPrex process can be designed as one‐reactor or two‐reactor layout. The process mechanisms of pH increase by aeration and stripping, crystallization due to dosing of magnesium chloride, and sedimentation and harvesting of the mineral phosphorus product remain the same. Dewatering is done after treating the sludge in the AirPrex reactor.

The most relevant process mechanism is the controlled crystal growth in the separated sludge water, leading to high quality products of specific size, of easy dewaterability, and of high purity. The reactor design of these processes can be summarized as follows:

  • Crystalactor: Cylindrical, upflow fluidized bed reactor with large crystallization surface, mainly on surface of sand seedings (in principle also other seedings possible), classification according to particle size in the fluidized bed, operational conditions leading to low supersaturation (metastable region), and recycle flow for dilution.
  • Pearl process: Upflow fluidized bed reactor with zones of increasing diameter, self‐seeding systems (struvite crystals are the seedings themselves), classification according to changes in diameter, operational conditions leading to low supersaturation (metastable region), and recycle flow for dilution.
  • Struvia process: Continuous stirred tank reactor with integrated solid–liquid separation by calming zone and lamellar packing (Turboflo™) or with additional lamella settler (Turbomix®). In the latter case, part of the struvite harvested from the bottom of the settler is recycled into the mixing reactor in order to reduce the amount of nucleation and to obtain crystals with larger particle sizes.

The implementation of struvite recovery from the sludge water (no matter if done prior or after dewatering) does not reduce the efficiency of technologies aiming to recover the phosphorus from the solid phase of the sludge, as done with acid leaching or thermochemical treatment of sludge ash. Phosphorus extraction is started by addition of sulfuric acid (2.8 l/m3 H2SO4 (96%)) to adjust a pH around 4. On the one hand, lowering the pH leads to a transformation of not readily soluble phosphate species into better soluble phosphate species (H2PO4− /HPO42−) (Falbe and Regitz, 1995). On the other hand, pH values below 5 can induce cell destruction and therefore result in phosphorus release (Kunst, 1991). After a reaction time of 0.5 h, a PO4–P concentration of around 500 mg/l was achieved, which means that roughly 66% of the total phosphorus content of the sludge was brought into solution. In a phosphorus precipitation reactor, after the first separation step, the remaining liquor that contains most of nutrients (phosphorus, ammonium, calcium, and magnesium) is pumped in the phosphorus recovery unit, consisting of two redundant stainless steel reactors with 16 m3 each operated in batch mode. The precipitation process is initiated by dosage of magnesium hydroxide (0.15 l Mg(OH)2 (53%) per m3). Due to the alkaline properties of the hydroxide, the pH is slightly raised to pH 6–6.5. After a reaction time of 0.5 h, sodium hydroxide (1.74 l NaOH (50%) per m3) is dosed to the solution to raise the pH to 9.3–9.4. After 0.5 h reaction time, the precipitated nutrients are separated from the process solution by a centrifuge and the addition of polymer. The dosage of magnesium is under stoichiometric with reference to phosphate in solution to force precipitation of calcium and prevent scaling in the subsequent ammonium stripping unit.

About 40% of the phosphate in the product is bound as struvite (MgNH4PO∙6H2O), 5% as vivianite (Fe3(PO4)∙8H2O), and 55% as calcium phosphate (supposedly hydroxyapatite with low calcium content: Ca9(PO4)5(HPO4)∙OH). The product obtained directly after dewatering has a solid content of 35–40%, which increases quickly by air‐drying to greater than 80%. Table 15.19 shows site‐specific data for the installation of the process in Gifhorn.

Table 15.19 Site‐specific data for the Gifhorn process.

Site‐specific data for the Gifhorn process Data
Size of the WWTP (p.e.) 50 000
Throughput of digested sludge (m3/day) 108 (with 2% TS)
P extraction rate from sludge 66.1 % (for pH 4)
Liquor specific phosphorus yield (%) 93.3%
Sludge specific phosphorus yield (%) 48.7%
Energy consumption including dewatering (kWh/m3 sludge) 7.6
Energy consumption without dewatering (kWh/m3 sludge) 4.5
Energy consumption including dewatering (kWh/kg P in product) 21.6
Energy consumption without dewatering (kWh/kg P in product) 12.9
H2SO4 (96%) (kg/kg P recovered) 14.6
Na2S (15%) (kg/kg P recovered) 8.9
NaOH (50%) (kg/kg P recovered) 2.3
Polymer (100%) (kg/tDM) 14
Molar ratio of magnesium to phosphate (—) 0.19
Percentage of P in the product (weight%) 11.0–12.0

Table 15.20 shows significant amount of chemicals required in the processes. As a result, both the capital cost and the O&M cost are usually very high. All technologies contain an initial sludge treatment step – the dissolution of P from the solid into the aqueous phase – to increase the concentration of dissolved phosphorus in the aqueous phase.

Table 15.20 All the P recovery process components.

Extraction process Metal elimination process Precipitation process
AirPrex × × Airlift reactor
Crystalactor® × × Upflow reactor
Pearl × × Upflow reactor
Struvia (Turbomix/Turboflo) × × Continuous stirred tank reactor
Gifhorn Dosing of H2SO4 NAS precipitation Precipitation and centrifugation
Stuttgarter Dosing of H2SO4 Complexation with citric acid Precipitation and sedimentation
Budenheim CO2 extraction × Precipitation

According to the different process components, several chemicals are consumed. All processes include a precipitation step and hence require the dosing of cation ions such calcium or magnesium. The three processes with an extraction process apply an acidic pH. For the pH increase before precipitation or crystallization, dosing of caustic soda is required. Processes without acidic treatment need a slight adjustment of pH but not necessarily depending on the properties of the sludge. A summary of types of chemicals applied in the processes is given in Table 15.21.

Table 15.21 Summary of chemicals used for the different concepts.

Extraction process Metal elimination process Precipitation process
AirPrex × × MgCl2 (33%), NaOH (30%), or CaCl2
Crystalactor® × × Mg(OH)2, NaOH, or MgCl2 upflow reactor
Pearl × × MgCl2 (33%), NaOH
Struvia (Turbomix/Turboflo) × × MgCl2 (33%)
Gifhorn H2SO4 (96%) NAS precipitation (15%) Mg(OH)2 (53%), NaOH (50%)
Stuttgarter H2SO4 (78%) Citric acid (50%) MgO (92%), NaOH (22%)
Budenheim CO2 × Lime

By adding magnesium components and increasing the pH, most of the processes precipitate or crystallize MAP (struvite). The product of AirPrex, Crystalactor, Pearl, and Struvia processes is a nearly pure struvite. The processes Crystalactor and Struvia are designed to produce calcium phosphate as an alternative product. The product of the Gifhorn and Stuttgarter process contains mainly struvite but also calcium and iron phosphates. The operational experiences differ significantly for the different technologies in terms of plant size and duration of operation. Table 15.22 gives an overview of the duration and sizes of installations of the processes. N and P recovery has positive impact on the operation of the WWTP, which are a reduced phosphorus load for the biological wastewater treatment and a reduction of the amount of sludge to be disposed. All processes that produce struvite additionally reduce the load of ammonium for the biological wastewater treatment. Furthermore all of them reduce the risk of encrustations in the sludge treatment part of the WWTP. However, this positive effect is mainly relevant for WWTPs using enhanced biological phosphorus removal and anaerobic digestion since otherwise the redissolution of phosphorus during the digestion is relatively low.

Table 15.22 Overview of size and duration of operation.

Duration Scale
AirPrex >2 years Full scale, several sites
Crystalactor® >2 years Full scale, several sites
Pearl >2 years Full scale, several sites
Struvia (Turbomix/Turboflo) >1 year Pilot scale, one site
Gifhorn Months/>2 years Full scale, one site
Stuttgarter >2 years One demonstration site
Budenheim >1 year Lab scale

15.5.2 Capital Cost of P Recovery Systems

To estimate the capital and O&M costs of different process for P recovery, the US EPA provides the following examples. Table 15.23 lists the capital cost of eight recovery systems (Tables 15.24 and 15.25; Figures 15.4 and 15.5).

Table 15.23 Capital cost of the eight designs.

Process Flow (MGD) Total construction cost (1978 $×106) Total indirect cost (1978 $×106) Total capital cost (1978 $×106) Total capital cost (2004 $×106)
Engineering Contingency
AS 1.0 2.24 0.34 0.34 2.91 7.36
10.0 12.03 1.80 1.80 15.64 39.53
20.0 19.95 2.99 2.99 25.94 65.56
50.0 38.95 5.84 5.84 50.64 127.99
100.0 64.60 9.69 9.69 83.98 212.28
AO 1.0 2.72 0.41 0.41 3.54 8.94
10.0 14.27 2.14 2.14 18.55 46.89
20.0 23.51 3.53 3.53 30.56 77.25
50.0 45.48 6.82 6.82 59.12 149.45
100.0 74.92 11.24 11.24 97.40 248.29
AAO 1.0 2.95 0.44 0.44 3.84 9.69
10.0 16.59 2.49 2.49 21.57 54.52
20.0 27.90 4.19 4.19 36.27 91.68
50.0 55.47 8.32 8.32 72.11 182.28
100.0 93.29 13.99 13.99 121.28 306.55
AAO + Al 1.0 2.97 0.45 0.45 3.86 9.76
10.0 16.63 2.49 2.49 21.62 54.65
20.0 27.95 4.19 4.19 36.34 91.84
50.0 55.55 8.33 8.33 72.22 182.54
100.0 93.42 14.01 14.01 121.45 306.98
AAO + Al + S 1.0 3.08 0.46 0.46 4.00 10.12
10.0 17.05 2.56 2.56 22.17 56.03
20.0 28.68 4.30 4.30 37.28 94.24
50.0 57.39 8.61 8.61 74.61 188.58
100.0 97.06 14.56 14.56 126.18 318.94
AAO + Al + S + F 1.0 3.30 0.50 0.50 4.29 10.84
10.0 17.87 2.68 2.68 23.23 58.72
20.0 30.45 4.57 4.57 39.58 100.06
50.0 62.81 9.42 9.42 81.65 206.39
100.0 104.81 15.72 15.72 136.25 344.41
AAO + Al + S + C 1.0 3.38 0.51 0.51 4.40 11.11
10.0 20.05 3.01 3.01 26.07 65.88
20.0 34.38 5.16 5.16 44.69 112.97
50.0 72.39 10.86 10.86 94.11 237.87
100.0 125.06 18.76 18.76 162.58 410.95
AAO + Al + F + UF 1.0 / / / / 12.27
10.0 / / / / 72.79
20.0 / / / / 113.18
50.0 / / / / 277.31
100.0 / / / / 486.18

Table 15.24 The O&M cost estimates for the eight processes.

Process Flow (MGD) Maintenance (2004 $×106) Taxes and insurance (2004 $×106) Labor (2004 $×106) Electricity (2004 $×106) Chemicals (2004 $×106) Residuals management (2004 $×106) Total O&M cost (2004 $×106)
AS 1.0 0.29 0.15 0.41 0.05 0 0.03 0.93
10.0 1.58 0.79 1.11 0.32 0 0.33 4.13
20.0 2.62 1.31 1.7 0.55 0 0.66 6.84
50.0 5.12 2.56 3.11 1.13 0 1.65 13.57
100.0 8.49 4.25 5.16 1.95 0 3.31 23.16
AO 1.0 0.36 0.18 0.45 0.07 0 0.03 1.09
10.0 1.88 0.94 1.24 0.45 0 0.34 4.85
20.0 3.09 1.55 1.88 0.78 0 0.68 7.98
50.0 5.98 2.99 3.45 1.60 0 1.71 15.73
100.0 9.93 4.97 5.76 2.77 0 3.42 26.85
AAO 1.0 0.39 0.19 0.48 0.07 0 0.04 1.17
10.0 2.18 1.09 1.33 0.45 0 0.38 5.43
20.0 3.67 1.83 2.1 0.78 0 0.75 9.13
50.0 7.29 3.65 3.85 1.62 0 1.88 18.29
100.0 12.26 6.13 6.61 2.8 0 3.77 31.57
AAO + Al 1.0 0.39 0.2 0.49 0.07 0.005 0.2 1.35
10.0 2.19 1.09 1.33 0.45 0.05 1.99 7.1
20.0 3.67 1.84 2.1 0.78 0.1 3.97 12.46
50.0 7.3 3.65 3.85 1.62 0.24 9.93 26.59
100.0 12.28 6.14 6.61 2.81 0.48 19.85 48.17
AAO + Al + S 1.0 0.4 0.2 0.5 0.07 0.007 0.23 1.41
10.0 2.24 1.12 1.35 0.46 0.07 2.26 7.5
20.0 3.77 1.88 2.12 0.79 0.15 4.51 13.22
50.0 7.54 3.77 3.89 1.62 0.37 11.29 28.48
100.0 12.76 6.38 6.69 2.81 0.75 22.57 51.96
AAO + Al + S + F 1.0 0.43 0.22 0.52 0.08 0.007 0.23 1.49
10.0 2.35 1.17 1.42 0.48 0.07 2.33 7.82
20.0 4 2 2.24 0.84 0.15 4.65 13.88
50.0 8.26 4.13 4.14 1.76 0.37 11.64 30.3
100.0 13.78 6.89 7.26 3.08 0.75 23.27 55.03
AAO + Al + S + C 1.0 0.44 0.22 0.61 0.08 0.008 0.24 1.60
10.0 2.64 1.32 1.53 0.51 0.08 2.37 8.44
20.0 4.52 2.26 2.34 0.89 0.16 4.74 14.91
50.0 9.51 4.76 4.21 1.87 0.41 11.85 32.61
100.0 16.44 8.22 7.1 3.31 0.81 23.7 59.58
AAO + Al + F + UF 1.0 0.49 0.25 0.66 0.09 0.02 0.25 1.76
10.0 2.91 1.46 1.50 0.62 0.19 2.5 9.18
20.0 4.53 2.26 2.33 1.12 0.38 5 15.62
50.0 11.09 5.55 4.25 2.46 0.95 12.5 36.80
100.0 19.45 9.72 7.39 4.49 1.90 25 67.95

Table 15.25 Estimated effluent quality of the eight reference designs.

Process TBOD (mg/l) TSS (mg/l) TP (mg/l) P removal (%)
Influent 174 172 7.5 /
Effluent of AS 22 20 5.86 21.8
Effluent of AO 11–20 20 4.12 45.1
Effluent of AAO 11 20 2.95 60.7
Effluent of AAO + M 10 20 1.00 86.7
Effluent of AAO + M+ S 5–10 5 0.325 95.7
Effluent of AAO + M+ S + F 5 1 0.145 98.1
Effluent of AAO + M+ S + C <1 <1 0.10 98.7
Effluent of AAO + M + F + UF <1 <1 0.05 99.3
Total capital cost ($) vs. total P removal (%) displaying 5 curves representing 1 mgd (dark solid), 10 mgd (dark dashed), 20 mgd (dotted), 50 mgd (light solid), and 100 mgd (light dashed).

Figure 15.4 Capital cost curves of the eight designs.

Annual O&M cost ($) vs. total P removal (%) displaying 5 curves representing 1 mgd (dark solid), 10 mgd (dark dashed), 20 mgd (dotted), 50 mgd (light solid), and 100 mgd (light dashed).

Figure 15.5 Annual O&M costs for the eight designs.

15.5.3 Activated Sludge

15.5.4 Two‐Stage Activated Sludge

15.5.5 Three‐Stage Activated Sludge

15.5.6 Three‐Stage Activated Sludge with Alum Addition

15.5.7 Three‐Stage Activated Sludge with Alum and Tertiary Clarifier

15.5.8 Three‐Stage Activated Sludge with Alum, Tertiary Clarifier, and Filtration

15.5.9 Three‐Stage Activated Sludge with Tertiary Clarifier and Activated Aluminum Absorption

15.5.10 Three‐Stage Activated Sludge with Tertiary Clarifier and Activated Absorption

15.6 Entrepreneur in SEE

To truly sustainably manage urban water and wastewater infrastructure, SEE attempts to change the paradigm of traditional design of GI, WTP, and WWTPs. More importantly, innovation and entrepreneur also play a critical role in creative design. Entrepreneur refers to individuals who create their own small business or individuals working for someone else that develop new ventures within their current institution. Before you create your new business, you need to answer: (i) Do I have what it takes to be successful? (ii) Am I starting a business where real and lasting opportunities exist? Managing a small business includes accounting, personnel management, and marketing. Successful entrepreneurs should be (i) opportunity seekers, (ii) future oriented, (iii) committed to being the best, (iv) market driven and customer oriented, (v) team players, (vi) realistic, (vii) tolerant of the tedium, and (viii) resilient. In addition, they should have experience in EE business including design, construction, and O&M of EEIS. Also they should clearly understand the nature of the products, services, customer needs, employees, suppliers, and seasonality in SEE industry.

Designing for environments involves (i) ease of disassembly, ease of cleaning, inspection, part replacement, and reassembly, (ii) reusable modular components, and (iii) few fasteners and interfaces. Since the 1970s, products were designed to minimize waste, resources, and energy to achieve a sustainable society. Later, circular economy attempts to minimize material, energy, and water flow without restricting economic growth or social and technical progress. Currently, zero water, wastes, and energy (3Z) is popular in building sustainable communities across the United States. One of the approaches is from cradle to cradle in product design by minimizing wastes through following strategies:

  1. Product design should be optimized for durability, remanufacturing, and recycling.
  2. Remanufacturing and preserving the stable frame of a product after use and replacing only worn‐out parts.
  3. Leasing instead of selling wherein the manufacturer’s interest lies in durability.
  4. Manufacturers should guarantee low pollution use and easy reuse.

Traditional box thinking sets controllable and measurable limits or useful restraints. On the other hand, thinking out of the box refers to knowledge and skill to do creative work, techniques for taking new perspectives on problems and for incubating and persevering on difficult problems, and taking risks with solutions to problems and the desire to solve the problem. Breaking out of box includes the following: (i) relook at the box you think you are in; (ii) look within to solutions you have never considered or can reconsider from the past; (iii) visit other boxes, within or without your organization; (iv) experiment at least part of the time with having no boxes; (v) encourage the use of virtual or transparent wall material for your box; and (vi) teach others the benefits of out‐of‐the‐box thinking. In general, out‐of‐the‐box thinking skills include the following:

  1. Common assumption that creativity is something you have or haven’t got.
  2. Appropriate techniques can bring out anyone’s creative potential.
  3. Creativity to the extent that it is now a practical business discipline.
  4. Traditional management practices predate the current frenetic pace of change.
  5. Creativity is one of a new set of skills necessary to manage in today’s business environment.
  6. Different ways to think outside the box.

15.6.1 Business Plan

The most important step in entrepreneurial world is a good business plan. Typical business plan should have the following components as shown in Table 15.50.

Table 15.50 Business plan for SEE designers.

Executive summary Topics Questions
Table of contents
Overview of the concept 1 Description of market demand and size according to the TDPs of SEE a. What are the market sizes at city, state, country, and global scales?
2 Description of EEIS design b. Why innovative design of EEIS is better than traditional design?
3 Identify options of EEIS c. Is to quantify your design or products significantly better than traditional design in terms of cost or environmental impacts?
4 Market analysis of each EEIS design option a. Is it for new design or retrofit?
b. How big is the market?
c. How many WWTPs will be impacted?
d. What is the competition?
e. What are the drivers of your design, energy efficiency, or material recovery?
f. Will the government accept?
g. How to satisfy the regulatory requirements?
Business models 1 Build, operation, and transfer (BOT) a. What is the time frame?
2 Public–private partnership (PPP) b. What are the percentage from government and your private side?
3 Private finance c. What are the return rates?
Management team 1 Team leader a. How many people and in which area?
2 Technical leader and specialists b. What is the specific expertise required?
3 Financial analyst c. What are the experiences?
4 Contract specialist d. What are the bidding specifics?
5 Legal specialist e. What are the relevant laws?
Execution plan 1 Milestones a. What are the key achievements in a specific time frame?
2 Timeline b. What are the major deliverables in a specific time frame?
3 Financial plan a. Cash flow
b. Capital outlay
c. Funding source
d. Payback or breakeven analysis
e. Facilities/resources
Marketing strategy 1 How to obtain approval? a. Is the product matured?
2 To whom to present? b. Who are the consumers?
3 Format for presentation a. Who are the stakeholders?
b. How do the stakeholders get involved?
c. Short synopsis and briefing
d. Detailed written plan
e. Who are the stakeholders?
f. Why are they important to the decision process?
g. What do they want to hear?
h. What to deliver?
Technological risk 1 Risk identification a. How reliable is the technology?
2 Risk management strategy b. What is plan B if plan A did not go as planned?
3 Risk communication c. Are communications between technical and financial management people efficient and effective?

15.6.2 Finance of Environmental Infrastructure

In the United States, government loan programs, such as the Clean Water and Drinking Water State Revolving Loan Funds, will often carry lower interest rates than private bond issues. Capital acquisition costs will be different for the State Revolving Loan Fund (SRLF) financing and private capital. Government loan programs will have loan application and ongoing reporting‐related administrative costs. Private capital acquisition costs typically include financial advisory services, bond counsel, underwriting fees, rating agency fees, closing costs and fees, and bond insurance and will have a mix of recurring costs including those for reporting, accounting, and general administration. Further major project capitalization costs include contributions to specified reserves (e.g. reserve account needs related to annual principal and interest payments, for emergency repairs, and for replacements) or meeting coverage covenants imposed by the financing agency. There are no specific federal SRF requirements for reserves or coverage covenants, although many state SRF programs require one or the other. Through coverage covenants, state SRFs can require that O&M expenses are met and net annual revenues must equal some increment above 100% (e.g. 120%) of the annual debt service payments for principal and interest. Finance cost includes construction, e‐engineering and technical services, pilot studies, environmental review and permitting, bidding and contracts, administration and legal services, commissioning costs, and construction management (Table 15.51).

Table 15.51 Procedure in cost and benefit analysis.

Step Action
1 Account fully for all project capital costs
2 Account fully for operations and maintenance costs
3 Account for the impacts new projects may have on overall utility system costs and revenues
4 Develop a capital financing strategy
5 Determine current revenue adequacy and develop future revenue strategy

15.6.3 EEI Financing

Raising awareness of the true cost of water may be an effective way to involve the stakeholders in financing an EEIS project. Current water rates do not reflect the true cost of supplying drinking water. Replacing the nation’s aging pipes will require additional local investment through higher water rates. Also, a large portion of public supply water is used for watering lawns, flushing toilets, and washing clothes, which are referred as gray water and do not require potable water. Therefore, municipalities should promote the construction of separate lines for potable and nonpotable uses. In the United States, the SRF under the Clean Water Act authorizes minimum federal funding of $20 billion over 5 years. States are allowed to issue bonds for water infrastructure projects at an estimated $6–7 billion annually. The ASCE recommended that a federal Water Infrastructure Trust Fund should be established to finance the national shortfall in funding of infrastructure systems under the Clean Water Act and the Safe Drinking Water Act.

15.6.4 Financial Planning

Financial forecast contains income statement, balance sheet, and cash flow statement. The debt to equity ratio is also important. The income statement should include sales, cost of goods sold, administrative expenses, expenses, accounts receivable, and inventory. In addition, the most likely, most pessimistic, most optimistic, and expected value should be estimated. Cash flow statement should cover combination of the income statement and the balance sheet forecasts, the changes in the cash balance with time, the cash flow statement, the income statement (the monthly values), and the balance sheet (the period‐to‐period changes). A cash flow statement should include total and net operating cash inflows, priority outflows, discretionary outflows, and total financial flows.

15.7 Innovation in SEE

15.7.1 Innovative Technologies

The trillion‐dollar environmental markets in both China and the US require innovative products, technology, process, and systems from the SEE sector. Integrated approach and new concepts emerging from sustainable developments will present huge opportunities for an entrepreneur. For example, element management is practiced in Denmark, waste refinery is booming in European countries, and circular economy is implemented as eco‐friendly industrial park. Waste‐to‐energy becomes more and more dominant in China form in replacing facility landfills. Recognizing the damage by air, water, and soil pollution in China, the ambitious goals to build new smart community and urban city will provide new generation of EEIS designers’ golden opportunity to be the leaders of innovation, creation, and entrepreneur. Indeed, China’s investment in EEI is at its reflection point due to consistent low 2% of GDP having been spent in environmental protection annually because GDP was the only performance evaluation criteria of their leaders. Goldman Sachs predicted that about $1.2 trillion will be spent from 2016 to 2020 on EEI in areas such as solid waste, sludge treatment and disposal, air pollution, and soil remediation. This presents about 60% increase from $0.7 trillion spent in China from 2011 to 2015. In China, 0.77 billion people live in urban cities and this number is expected to be 1.00 billion by 2020. Currently, ecological civilization is on the core agenda for the current government in the next 5 years. New regulations such as 10 rules on air, water, and soil pollution control impose significant financial responsibilities for national and local governmental agencies to finance EEI at unpreceded pace in the following environmental technologies:

  1. Biological denitrification and phosphorus removal technologies.
  2. Membrane separation and manufacturing technologies and equipment.
  3. Manufacturing technology of anaerobic biological reactors.
  4. High‐concentration organic wastewater treatment technology and equipment.
  5. Standardized and modularized water and wastewater treatment equipment with high efficiency.
  6. Water‐saving technologies and equipment.
  7. Water treatment agents.
  8. Monitoring instruments.
  9. Natural water‐body rehabilitation technology.
  10. Artificial intelligence, cloud computing, big data, and wireless technologies.

Among all these technologies, consumer products related to water, air, and solid waste are also important markets for SEE entrepreneur to establish their business in China for one billion people without safe drinking water and decent sanitary infrastructure.

15.7.2 Innovative Consumer Products

15.7.2.1 SteriPEN

SteriPEN is a small pen‐like electronic device that emits an UV light and purifies either half a liter or one full liter of water at a time. The device operates off batteries and works with clear water by killing the DNA of harmful microbes and bacteria. A light wand sticks out of one end of the device – which gets submerged into the bottle of water. By pushing the button either once or twice, you can choose to purify a full liter of water or a half liter. The light turns on and stays on while you agitate the water with the light wand until the dose is complete. Once the water is safe to drink (about 1 min later), the light turns off and flashes green – if it flashes red, you have to repeat the dose because something went wrong (if you accidentally lift the wand out of the water during a treatment, a sensor will flag it that the water was not properly treated and flash red). The product website is http://www.steripen.com/.

Most models are reusable for up to 8000 l for over 7 years of safe drinking water. SteriPEN avoids plastic pollution by keeping thousands of plastic water bottles out of the waste cycle. UV light destroys over 99.9% of bacteria, viruses, and protozoa like Giardia and Cryptosporidium. SteriPEN is certified effective by the Water Quality Association and has won multiple industry awards. The major advantage is that travelers do not have to purchase bottled water by carrying Nalgene bottles with the SteriPEN.

15.7.2.2 Drinkable Book™

Dr. Theresa Dankovich from Carnegie Mellon teaming with WATERisLIFE introduced The Drinkable Book, the first ever instructional manual that provides safe water, sanitation, and hygiene education and serves as a tool to kill deadly waterborne diseases by providing the reader with an opportunity to create clean, drinkable water from each page and teaching methods and ways to share the message through training, storytelling, and discussions in communities and schools worldwide where there is a desperate need. Each book can provide a user with clean water for up to 4 years. WATERisLIFE has introduced a campaign to move into full production of the Drinkable Book. WATERisLIFE is working in partnership with the Drinkable Book on research and production. It plans to begin global distribution of the Drinkable Book in 2016.

SunSpringTM is a solar‐powered microbiological water treatment system. It is a lifesaver for entire communities, medical facilities, or schools. The SunSpring is Gold Seal Certified to the US EPA standard for microbiological water purifiers. The SunSpring physically removes particulate matter, turbidity, bacteria, viruses, and cysts from virtually any water source, including rivers, lakes, streams, ponds, shallow wells, rainwater, unsafe municipal supplies, and springs. This ultra‐purification technology is self‐contained, is designed for community‐level water output, and has an automated self‐cleaning maintenance system. Each SunSpring filtration unit can filter up to 5000 gal of clean water per day. WATERisLIFE has installed the first unit in Northern Haiti, providing clean water to 2000 residents per day. The company’s website is http://waterislife.com/clean‐water/new‐technology.

15.7.3 Future of SEE

By 2050, human population would reach 10 billion on this planet. 70% of the people will live in urban areas. If the design criterion is 100 gal/capita/day, the total WRRF capacity would be 0.7 trillion gallon/day. Since the average flow rate of WWTPs in the United States is 3 MGD, there would have 233 000 WWTPs by 2050. Therefore, the market for SEE designers to either retrofit the old WWTPs or to build new WRRFs is in trillion US dollars. In the United States and China alone over the next several decades, SEE designers are fortunate to have a trillion‐dollar market to apply the TDPs of the SEE to design sustainable EEIS. If all the 15 000 WWTPs in the United States and 5 000 WWTPs in China were to be retrofitted to WRRFs, these two markets could be $0.5 trillion dollars, respectively. The SEE TDPs could also transform the design of air, and solid waste management infrastructure systems is another half trillion market. Therefore, a trillion‐dollar market is waiting for the future SEE designers to take the lead. The roadmap could be simple: after a decade, 100% water reuse rate by 2030, energy neutral or positive by 2040. By 2050, the standardized and modulated WRRFs could be significantly more economic than current WWTP. As a result, nutrients and materials were recovered at the WRRFs, which could be revenue generating facilities instead of a liability of a water utility by 2050.

To achieve these ambitious targets, fast adoption of innovative technologies would increase both the reliability and resiliency of EEIS. For example, 3D printing could produce a model of a unit process or a system of minimal footprints in just a few days. Mobile wireless technologies could monitor environmental parameters at real time. Supervisory control and data acquisition (SCADA) could monitor and optimize the integrated EEIS in real time. One important application of SCADA is to forecast the infiltration/inflow through sanitary sewer system according to anticipated precipitation. As computer and internet technologies advances, deep learning, machine learning, and artificial intelligence could help SEE designers to achieve performance metrics and energy benchmarks of EEIS. Internet of Things (IoT) could connect millions of water meters through the Internet and eliminate manual reading of water meters. Sensor technologies and automatic control system could adjust the precise ratio of NH3:NO2− to achieve the maximal efficiency of Anammox. Virtual reality changes the way we educate and train plant personnel. Mining data pattern from big data of water distribution and use could identify major leak to reduce water loss. Cloud computing would increase computing capacity and allow SEE designer’s access sophisticated software, which might not be accessible to current engineers. Blockchain technology significantly reduces the cost of the governmental bidding and procurement. For these reasons, SEE designers should keep an open mind and track all the new technology breakthrough and apply them to their design. When SEE designers systematically apply the TDPs and continuously update their knowledge on innovative technologies, human society and economic prosperity could be decoupled from environmental degradation. Only in this way human would coexist with the nature in harmony!

15.8 Exercise

15.8.1 Questions

  1. Optimal pipe diameter is determined by what costs?
  2. AOP as emerging technology is to replace phase transfer processes such as carbon adsorption. Why AOP should be a better choice than carbon adsorption?
  3. What are the major causes preventing WWTPs to recover N and P?
  4. What are the key elements in developing a new technology?
  5. Why WTP and WWTP design have not changed for last 100 years, yet iPhone has its new product every year?
  6. What are the major areas in SEE markets that you would like to devote to develop, design, manufacture, and market new products?
  7. What are the market sizes of your new products in developed and developing countries, respectively?

15.8.2 Calculations

  1. Moving bed biofilm reactors (MBBR) separates solid retention time (SRT) from hydraulic retention time (HRT) by growing nitrification and denitrification bacteria on the biofilm fillers. It could significantly increase total nitrogen removal and reduce sludge production. If the aeration tank has volume of 30 000 m3 for a WWTP of 100 MGD, 60% will be filled with the filter media of the biofilm reactors, and the unit cost of the filter media is $500/m3, answer the following questions:
    1. What would be the total cost of the filter media of the biofilm reactor if the aeration tanks be filled with 60% of the biofilm reactors?
    2. If the N and P concentration of wastewater effluent is significantly decreased from 17 and 1 mg/l to 1 and 0.02 mg/l, respectively, 40 MGD of the discharge effluent could be reused for irrigation and recharge the aquifer. How many years of the retrofitting capital cost could be recovered due to the water reuse if the reclaimed water is valued at $3/1000 gal?
  2. If Miami‐Dade Water and Sewer Department (WASD) is to design and build the state‐of‐the‐art 40 MGD West Dade WRRF with nutrient recovery, estimate the capital and O&M costs in recovering nutrients of eight different processes by using the examples presented in this chapter. If the West Dade WRRF is to use the reclaimed water for irrigation or aquifer recharge, conduct the life cycle cost and benefit analysis and estimate the years of return of capital cost of this WRRF.

15.8.3 Projects

To effectively design SEEI system, six criteria are listed as follows:

  1. All the GI, WTP, and WWTP have to be modulated and standardized so that further expansion and retrofitting are easy to achieve. When the industry shifts to pipe reactors, critical technologies such as FO, MBR, MF, NF, RO, and SPVR will be designed according to the same industrial standards.
  2. Decentralized WWT should be encouraged to break utility monopoly. As a result, competition will brew innovation and race with time. If there was no competition, Tesla will not invent his alternative current electrical generator, Wright brothers would delay in building their first airplane, and Bill Gates would not launch his first Window operating system so quickly. Under competition, each player will be challenged and pressurized to deliver her/his maximal potential.
  3. Students should be introduced to at least three critical industrial trend setting technologies in designing WRRFs. More importantly, the students should be motivated to stay on the technology as early and as long as possible. Throughout the students’ curriculum, students should be motivated so much that by the end of graduation, meaningful creative design or innovation should be expected under the mentoring of professors.
  4. According to SEE students’ academic strength and personal passion, each student should select at least one critical technology. Product development as well as innovative design or solving one community environmental unsustainable problems by using modern design tools should start from this course. Students should stay with the problem by following peer‐reviewed journal papers and current industrial products.
  5. Complicated environmental problem should be broken into several pieces. Each group will then be in charge to solve smaller problems under the leadership of team leader. Different students have different passion and skills. More importantly, the team needs to incorporate electrical engineers for electrical control by SCADA, mechanical engineers for innovative design of critical technologies, and computer scientists to optimize the process and automatic control and monitoring of WTP or WWTP.
  6. SEE students need to learn how to effectively pitch their innovative products to the financial market. Chinese industrial parks served as powerful bridges between academy and industry. Since most industrial parks are located so close to major universities, many would be garage inventors that are nurtured in the industrial parks. SEE students should select one product to collect information on its design, improvement, and manufacture. All the key components need to be updated as technology advances.

According to the aforementioned six criteria, develop a comprehensive business plan for Xiongan and your hometown that you have chosen.

15.8.3.1 Xiongan Project

  1. Develop a business plan for Xiongan to achieve zero water, waste, and energy in 5, 10, 20, and 50 years.
    1. What are the major design variables?
    2. What are the major challenges?
    3. What are the major strategies to achieve 3Z?
  2. Design integrated air, water, solid waste, and soil management system that can be used for Xiongan in the next 5, 10, and 50 years using the TDPs of SEE. Your design has to be assessed according to life cycle cost and benefit analysis. Write one milestone for your venture to establish an innovative company and make it specific to your product or service.
  3. Propose milestone for your venture and make it specific to your product or service.
  4. Develop a list of events for your venture and develop a flow diagram showing the relationship between the events for your venture.
  5. Discuss how the events selected relate to the assumptions you have developed. Do you have at least one event for every assumption?
  6. Which events are time sensitive? Why?
  7. What skills, abilities, and knowledge should an SEE entrepreneur have?
  8. What kind of education, work experience, and motivation should an SEE entrepreneur have?

Project 1:

The major environmental challenges in Xiongan district are the following:

  1. Current heavy and vast pollution of air, water, and soil.
  2. Energy structure is coal‐based power.
  3. Old industrial and agricultural plants and farms.

Using TDPs that you learned and computer skills you mastered, develop design alternatives for retrofitting current WWTPs in the district and remediation of contaminated air, water, and soil.

Project 2:

  1. Develop alternatives that include the type of technologies and how it will be installed and operated on building, community, city, and the special district. Develop renewable energy alternatives to replace electricity from coal due to its high pollution rates.
  2. Develop specifications, drawings, and calculations of each alternative in achieving zero energy with minimal environmental impacts using LCA and life cycle cost and benefit analysis.

Project 3:

  1. Design zero water on house, community, city, and the special district scales.
  2. Design color‐coded system for blue, green, gray, brown, and black water to achieve zero water design.
  3. Each alternative should be assessed using the LCA.
  4. Provide any applicable specifications or drawings to demonstrate the system design and location.

Project 4:

Develop a comprehensive resource recovery strategy plan:

  1. Type of resources such as water, energy, and nutrients to be recovered.
  2. Descriptions and specification on system used.
  3. Estimated annual quantity recovered.
  4. Estimated impact on total building resource production (i.e. approximately what percent of the identified resource is recovered).
  5. What are the strategies that support both sustainable communities and green infrastructure?
  6. How to organize stakeholders.
  7. Use three color‐coded strategies to reduce use of potable water for irrigation purposes.
  8. What are the efficiency standards for plumbing fixtures?
  9. How much deep‐well geothermal energy is available?
  10. What are the recommendations according to life cycle assessment and cost–benefit analysis, respectively? Why is the recommendation of different alternatives?

15.8.3.2 Community Project Proposal

  1. Students should compile the inventory data from their corresponding hometown on following:
    1. Annual industrial production.
    2. Annual agricultural production.
    3. City population and predicted population in the next 5, 10, 20, and 50 years.
  2. Use the US EPA emission factor handbook to estimate the following:
    1. Total annual air, water, and soil pollutants.
    2. What are the net pollutants that may subject to environmental tax and estimate environmental tax on each category of pollutants?
    3. Estimate the market size for air, water, and soil pollutants.
  3. Develop a business plan on retrofitting GI, WTP, and WWTPs in your local community according to the business plan outline in this chapter. Do the same as above for your community.

15.8.3.3 Course Project and Beyond

The Xiongan project has a much bigger purpose. It attempts to develop true sustainable modern urban smart city to achieve zero water, waste, and energy design. It is a flagship of new urban design and construction for China's One Belt and Road initiative. Therefore, in the EEIS design, theoretical potential, benchmark data, design standards, and actual technical parameters should be carefully evaluated so that design standards, codes, and criteria can be developed for zero water, waste, and energy according to the TDPs. The key to make major contribution to SEE design is to apply the TWPs of SEE in different EEIS design on different spatial and temporal scales. More importantly, all the developed technical standards, codes, and criteria should be rapidly adopted across the country to replace the traditional unsustainable EE design to decouple environmental deterioration from economic development. As a result, we can coexist with the nature in harmony for generations to come.

References

  1. Cullen, N., Baur, R., and Schauer, P. (2013). Three years of operation of North America’s first nutrient recovery facility. Water Science & Technology 68 (4): 763–768.
  2. Falbe, J. and Regitz, M. (1995). Römpp Chemie Lexikon, 9. Auflage, Band 4, S. 3386 ff. Stuttgart: Thieme Verlag.
  3. Kabbe, C. (2015) Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency. P‐REX project report. Berlin: Kompetenzzentrum Wasser Berlin gGmbH.
  4. Kunst, S. (1991). Untersuchungen zur biologischen Phosphorelimination im Hinblick auf ihre abwassertechnische Nutzung. Hannover: Veröffentlichungen des Institutes für Siedlungswasserwirtschaft und Abfallwirtschaft, Heft 77.
  5. Pinnekamp J., Baumann, P., Cornel, P. et al. (2013). Stand und Perspektiven der Phosphorrückgewinnung aus Abwasser und Klärschlamm – Teil 1, KA Korrespondenz Abwasser. Abfall, 60/10, 837–844.
  6. Pinnekamp, J., Montag, D., Gethke, K. et al. (2007). Rückgewinnung eines schadstofffreien, mineralischen Kombinationsdüngers Magnesiumammoniumphosphat – MAP aus Abwasser und Klärschlamm. UBA‐Texte 25/07, Dessau‐Rosslau.
  7. US Environmental Protection Agency (2005). UV disinfection guidance manual. EPA. Office of Water.
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