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Effect of co-managing organic waste using municipal wastewater and solid waste treatment systems in megacities Masaki Takaoka, Kazuyuki Oshita, Takahiro Iwamoto and Tadao Mizuno

ABSTRACT A model was developed to calculate the mass and heat balances of wastewater and municipal solid waste treatment plants when these plants operate either separately or together with a mutual dependence on mass and energy. Then the energy consumption, life cycle costs (LCCs), greenhouse gas (GHG) emissions and effluent quality were evaluated under various scenarios to identify the most effective co-management and treatment system. The results indicated that co-digestion of kitchen waste and sewage sludge, and their co-combustion reduced LCCs by 30%, energy consumption by 54% and GHG emissions by 41% compared to the base case. However, co-digestion increased the total nitrogen load in the wastewater treatment plant effluent. Even if an advanced wastewater

Masaki Takaoka (corresponding author) Kazuyuki Oshita Takahiro Iwamoto Tadao Mizuno Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, C-cluster, Kyotodaigaku-katsura, Nishikyo-ku, Kyoto 615-8540, Japan E-mail: [email protected]

treatment system was applied to improve total nitrogen concentration, the above indicators were affected but still reduced compared to the base case. Therefore, it was confirmed that the integrated system was beneficial for megacities. Key words

| co-management, energy consumption, lifecycle costs, municipal solid waste, organic waste, wastewater

INTRODUCTION In megacities, large amounts of energy and resources have been consumed following rapid economic growth, urbanization and the widespread improvement in living standards. Alongside increases in municipal solid waste (MSW) and sewage sludge production, greenhouse gas (GHG) emissions have also increased in megacities. To mitigate GHG outputs, the efficient use of resources and energy in the municipal wastewater and solid waste treatment systems of megacities is important. Thus, appropriate methods of handling organic waste, such as kitchen waste and sewage sludge, must be developed. In this study, we assessed the current municipal wastewater and solid waste treatment systems comprehensively and quantitatively, focusing on organic waste such as kitchen waste and sewage sludge in Japan as Japan has two megacities, namely, Tokyo and Kansai, and both systems are currently not integrated although synergistic positive effects are expected. In Japan, 45 million tons of MSW were generated in 2010 and about 80% of MSW was incinerated (Ministry of the Environment Japan ). However, approximately 30–40 wt.% of MSW is doi: 10.2166/wst.2013.777

kitchen waste, which has a high moisture content and decreases the lower heating value (LHV) of MSW. On the other hand, approximately 2.2 million dry base (DS)-t of sewage sludge is produced each year and the amount is gradually increasing with the expansion of wastewater treatment plants (WWTPs). Approximately 31 wt.% of the total amount of sewage sludge (0.69 million DS-t) is used in methane fermentation tanks annually, but few examples of co-digestion with kitchen waste have been reported. After a dewatering process, approximately 68 wt.% of sewage sludge (DS base) is incinerated in WWTPs separately from MSW ( Japan Sewage Works Association ). Here, we developed a model to calculate the mass and heat balance of wastewater and MSW treatment plants when these plants operate either entirely separately or together with a mutual dependency on mass and energy and calculated the energy consumption, operating costs, GHG emissions and effluent quality for several scenarios. On the basis of the results, we identified the most effective co-management and treatment system.

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METHODS Scale and input data of WWTP and MSWI For our model, we assumed that a WWTP and a MSWI (municipal solid waste incinerator) treated the sewage sludge and MSW generated in a megacity of 1,260,000 people in Japan. As the base case, we set 400,000 m3/day as the planned sewage treatment quantity of the WWTP from the specific sewage-generation rate reported for Japan: 0.32 m3/day/capita (Japan Sewage Works Association ). For wastewater, sludge and waste transfers between the WWTP and MSWI in each scenario (explained further below), the scale of the WWTP or digestion tank was altered appropriately, based on a mass balance calculation. Table 1 shows the influent quality to the WWTP. As will hereinafter be described in detail, four fractions of total solids (volatile suspended solids: VSS, volatile dissolved solids: VDS, fixed suspended solids: FSS, and fixed dissolved solids: FDS) were calculated for each process. In addition, the quantity of flow (Q), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) were calculated for the wastewater treatment system operating at a steady state. Each value in Table 1 was determined from data for a WWTP with a separate sewerage system (Shomura et al. ) located at Kansai area in Japan.

Table 1

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Influent quality to WWTP

Flow volume

m3/day

400,000

SS

mg/L

166

VSS

mg/L

144

VDS

mg/L

237

FSS

mg/L

23

FDS

mg/L

210

POC

mg/L

49

DOC

mg/L

53

TN

mg/L

30

PN

mg/L

10

SN

mg/L

19

TP

mg/L

4.0

PP

mg/L

4.6

SP

mg/L

2.4

DOC, dissolved organic carbon; PN, particulate nitrogen; POC, particulate organic carbon; PP, particulate phosphorus; SN, soluble nitrogen; SP, soluble phosphorus.

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As the base case, we then calculated 1,252 t/day as the anticipated quantity of MSW from the sewered population and adopted the reported MSW-generation rate for Japan: 0.99 kg/day/capita (Ministry of the Environment Japan ). As for the scaling of the WWTP, the scale of MSWI was altered appropriately, based on a mass balance calculation for each scenario. We used data for the MSW composition of Kyoto City because it has a similar population as this setting condition (Kyoto City Japan ). Table 2 shows the composition and characteristics of MSW used in this study. System boundaries and scenarios We considered the entire WWTP and the MSWI. A flow diagram of the system used in this study is shown in Figure 1. In a WWTP, thickened sludge or the mixture of thickened sludge, kitchen wastes and/or paper wastes is mesophilically digested by methane fermentation. Dewatered sludge is incinerated in a fluidized bed incinerator in a separate case. In a MSWI, only MSW or mixtures of MSW and dewatered sludge are incinerated in a stoker-type incinerator with a waste power generation system. The flue gas treatment consists of a bag filter for dust removal, a wet scrubber for acidic gases removal and a selective catalytic reduction (SCR) system for nitrogen oxides removal. Finally, flue gas is mixed with high-temperature air to prevent the appearance of white smoke. We did not consider sewer culverts, pumping stations and MSW collection systems because their alignments and scales vary widely with terrain. The following scenarios were evaluated. In scenario A, the WWTP and MSWI operated separately from one another. We then considered the six scenarios shown in Table 3 to evaluate the co-combustion of dewatered sludge with MSW in the MSWI (B, C, D, E and F), the treatment of wastewater from the MSWI in the WWTP (B, D and E), the co-digestion of kitchen wastes and sewage sludge in the WWTP (C, D and E), the co-digestion of kitchen wastes, sewage sludge and paper wastes in the WWTP (F) and the operation of A2O biological treatment in the WWTP (E and F). Models and evaluation indicators Referring to previous work by Oshita et al. (), Shomura et al. () and Takaoka et al. (), a combined WWTP and MSWI model was developed in this study. Although the calibration was not performed thoroughly in terms of the calculated results for life cycle costs (LCCs), energy consumption and GHG emissions, we have validated each

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Table 2

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Effect of co-managing organic waste in megacities

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Composition and characteristics of MSW in Japan

Weight

Water

Combustible

Ash

Bulk specific

LHVc

LHVw

MSW

percentage

content

content

content

density

(MJ/

(MJ/

C (%

H (%

O (%

N (%

S (%

Cl (%

P (%

category

(%)b

(%W.B.)

(%W.B.)

(%W.B.)

(kg/L)

kg)

kg)

D.B.)

D.B.)

D.B.)

D.B.)

D.B.)

D.B.)

D.B.)

Kitchen waste

39

79

18

3

0.39

20.4

1.7

46.6

6.9

41.7

3.8

0.1

0.4

0.5

Paper waste

34

20

78

2

0.15

17.0

12.8

44.2

6.0

49.2

0.2

0.0

0.4

0.0

Fiber

3.9

20

79

1

0.22

17.8

13.6

47.2

6.2

44.1

1.6

0.1

0.7

0.0

Wood

0.94

45

52

3

0.23

20.4

9.5

48.6

6.1

43.6

1.2

0.0

0.3

0.2

26

74

0

0.05

33.5

24.1

59.9

6.6

29.9

0.1

0.0

3.4

0.0

14

72

14

0.37

29.3

20.7

67.2

8.1

18.3

1.1

0.3

4.8

0.0

Plastics

14

Rubber

0.42

Glass

1.7

3

0

97

0.39

0

–0.08

0.0

0.0

0.0

0.0

0.0

0.0

0.0

Metal

2.7

10

0

90

0.1

0

–0.25

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0

97

1.22

Ceramics

2.8

3

Kerosene



0.01

Dewatered sludge



a

99.9 a

0.1



a

0.856

0

–0.08

0.0

0.0

0.0

0.0

0.0

0.0

0.0

43.5

43.5

85.9

13.6

0.5

0.0

0.0

0.0

0.0

a

a

a

a

a

a

a

a

a

LHVc, lower heating value (combustible base); LHVw, lower heating value (wet base); W.B., wet base; D.B., dry base. a

Values are calculated from the result of mass balance in WWTP.

b

Values are MSW base, dewatered sludge and kerosene were not included.

Figure 1

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Flow diagram of WWTP and MSWI in this study.

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Table 3

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Evaluation scenarios

Scenario

MSW and sludge cocombustion

Wastewater cotreatment

Co-digestion

Biological treatment in WWTP

A

Base case







B

Co-combustion and co-water treatment

O

O



Conventional activated sludge process

C

Co-combustion and codigestion

O



Sludge and kitchen waste

D

C þ co-water treatment

O

O

E

D þ A2O

O

O

F

E þ Paper waste digestion

O

O

system in previous studies and determined that a relative comparison of the results for each scenario was possible by calculating results for each process based on the same configuration (basic unit). For the purpose of this study, precisely calculating the amount of organic matter in sludge was important. The four fractions of total solids (VSS, VDS, FSS and FDS) were determined for each process. In addition, Q, TOC, TN and TP were calculated for the WWTP operating under steady-state conditions. MSW, ash (bottom ash and fly ash), waste gas, combustion air and chemical reagents used to treat waste gas were also calculated for the MSWI operating under steady-state conditions. A heat balance and mass balance of steam generated from the boiler were also calculated. We considered the construction and operating costs of the WWTP and MSWI using an exchange rate of 80 Japanese yen against the US dollar. When determining operating costs, the electric power, fuel, chemical, ash landfill, labor, maintenance and repairing costs were considered. The unit price of electric power purchased from the plant was set at 0.1674 dollar/kWh. A Feed-in Tariff scheme for renewable energy set the unit price of generated power from biomass in a MSWI, generated power from non-biomass in a MSWI and generated power from biogas in a WWTP at 0.2231, 0.06675 and 0.5119 dollar/kWh, respectively. We set conditions whereby all generated power could be sold but we assumed that the electricity requirements could not be covered by generated power but purchased from the electric utilities (The Kansai Electric Power Co. Inc. ). Furthermore, a plant has three stages, construction, operation and decommissioning, but estimating the impact of the first and last stages is difficult due to various uncertainties. The claim has also been made that the impact of the construction stage is less than that of the operation stage (Renou et al. ). Therefore, we only considered energy consumption

A2O process Sludge þ kitchen waste þ paper waste

and GHG emissions from the operation stage in this study. However, we calculated the LCCs including construction and operation cost over a 20-year period. Energy consumption was calculated including electric power and fuel consumption, and also including energy recovery from the biogas generated by digestion. The energy consumption for electric power was transformed into primary energy using the receiving end efficiency estimate of 0.369 [–], which was determined from the known power generation efficiency of a thermal power plant and its electric energy transmission loss. Energy consumption from fuel use was calculated on the basis of the densities and calorific values per unit of each fuel. GHG emissions (CO2, CH4 and N2O) were calculated and combined with CO2 equivalent emissions including the amount of GHG emitted directly from each treatment process (in the CO2 case, biomass derived CO2 were omitted) and GHG emitted indirectly from the production and consumption of energy and chemical reagents in each treatment process by GWP (100 years). In particular, N2O emission factors of wastewater treatment were 0.00016 kg-N2O/m3 for conventional activated sludge process and 0.000023 kg-N2O/m3 for the A2O process based on the actual measurements (Soda et al. ). Moreover, the emission factor of electricity is 0.555 kg-CO2/kWh which is generally used in Japan. Since the electrical mix about this emission factor is in 2005 in Japan, hydroelectric generation, nuclear electricity generation and thermal power generation are 8, 31 and 61%, respectively (Japan Agency for Natural Resources and Energy ). Based on these calculations, the quality of effluent (SS: mg/L, TOC: mg/L, TN: mgN/L, TP: mg/L) in the WWTP, LCC (dollars/20 years), energy consumption (MJ/year) and GHG emissions (t-CO2eq/year) were calculated. These seven indicators were used to evaluate and compare the combined WWTP and MSWI systems.

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RESULTS AND DISCUSSION Effluent quality Figure 2(a) shows the effluent quality from the WWTP in each scenario. Comparing scenario A to scenario B, no great influence of the co-combustion and wastewater cotreatment in the WWTP was observed on effluent quality. This is because the quantity of wastewater from the MSWI was much smaller than that produced by the WWTP. Comparing scenario C and D to scenario A, the TN concentrations in the effluent produced under both scenario C and D were 1.13 times higher than that produced under scenario A. This is because kitchen waste was co-digested with sewage sludge, and reverse water, including dewatered filtrate, had a higher concentration of TN in scenarios C and D, whereas the

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influence of TP in kitchen waste on the effluent quality was limited. In scenarios E and F, which included the A2O process in the WWTP, TN concentrations in the effluent decreased from 25.8 to 12 mgN/L. However, the TP concentrations of effluent in scenarios E and F were slightly higher than those in scenario C, despite the A2O process. This was likely to have been caused by TP removed from wastewater to excess sludge in the A2O process being re-eluted under the anaerobic conditions of the digestion tank and settling into the dewatered filtrate and reverse water (Matsuda et al. ). The median actual treatment target concentrations (TTCs) for SS, TN and TP, calculated from the Japan Sewage Works Association (), are 30 mg/L, 14 mgN/L and 1.9 mgP/L, respectively. Comparing these values with the calculated values from Figure 2, scenarios E and F were the most desirable for situations requiring strict water quality control at the effluent destination. Life cycle cost

Figure 2

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Effluent quality in WWTP and life cycle cost in each scenario.

Figure 2(b) shows the calculated LCCs for each scenario. In scenario B, compared with scenario A, the co-combustion of MSW and dewatered sludge in a MSWI with co-treatment of wastewater in a WWTP had little influence on the LCC. In scenario C, compared with scenario A, the construction cost of the WWTP increased by 0.34 × 108 dollars/20 years because it required a larger digestion tank, a kitchen waste crusher and a centrifugal dewatering machine. However, the construction costs of the MSWI, which accounted for the greatest proportion of the total construction cost, decreased by 0.48 × 108 dollars/20 years because the amount of MSW, including dewatered sludge, decreased by 30 t/day due to the co-digestion of sewage sludge and kitchen wastes. In terms of operating costs, fuel and chemical costs decreased by about 0.64 × 108 dollars/20 years. Moreover, 483 t/day of kitchen waste were placed into the WWTP digestion tank for co-digestion and biogas power generation, and the electricity cost in WWTP subsequently decreased by 4.15 × 108 dollars/20 years. The total LCC of scenario C was 5.33 × 108 dollars/20 years (about 30%) lower than that of scenario A. In scenario D, the LCC was 0.35 × 108 dollar/20 years lower than that of scenario C due to the wastewater co-treatment, which was the lowest of all the scenarios. Comparing scenario C to scenario E, the LCC of scenario E increased because of the introduction of the A2O process to the WWTP. Comparing scenario A to scenario E, the total LCC of scenario E was 3.7 × 108 dollars/20

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years lower than that of scenario A because the cost reduction of the co-digestion of kitchen wastes and sewage sludge in the WWTP was more effective than the cost increase due to the introduction of the A2O process. The introduction of the co-digestion of kitchen waste, sewage sludge and paper wastes in scenario F resulted in an additional decrease in the electricity costs in the WWTP. Incineration of dewatered sludge, including the digestion residue of paper wastes and kitchen waste and a separate MSWI handling materials without paper and kitchen wastes, increased the LCC by 3.06 × 108 dollars/20 years more than scenario E, largely because of the decrease in LHVw and the increased fuel cost for the MSWI. Energy consumption Figure 3(a) shows the energy consumption for each scenario. In scenario A, the energy produced from waste power generation was calculated to be 2.30 × 109 MJ/year.

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This value corresponded to 2.36 × 108 kWh/year in electricity production and to 516 kWh/t-waste in terms of electricity produced per ton of MSW as a base unit. The base unit of power generation for a MSWI with a 20% power generation efficiency was reported to be 600 kWh/twaste by Martin et al. (), which is almost the same as that found in this study. The energy consumption of the WWTP was approximately 4.4 × 108 MJ/year, as shown in Figure 3(a). This value corresponded to 3.02 MJ/m3 as the amount of energy consumed per m3 of wastewater as a base unit of energy consumption and fell within the previous range reported by Suda et al. (). Figure 3(a) shows that in scenarios A and B, the co-combustion of MSW and dewatered sludge in the MSWI with cotreatment of wastewater in the WWTP had little influence on the energy consumption between systems. Although in scenario B, energy consumption derived from fuel in sludge incineration was trivial, by decreasing the LHVw of the input waste to the MSWI and increasing the mass of waste, an increase in electricity and fuel consumption in the MSWI was required despite the increase in waste power generation. Comparing scenario A to scenario C, the co-digestion of sewage sludge and kitchen waste reduced the fuel consumption in both systems and increased the electricity generated from biogas. The energy consumption in scenario C was approximately 5.7 × 108 MJ/year lower than that in scenario A. However, the introduction of the A2O process to the WWTP increased energy consumption by 2.8 × 108 MJ/year due to the greater electricity usage in scenario E compared to scenario C. Co-digestion with kitchen waste, sewage sludge and paper wastes and the incineration of dewatered sludge in scenario F resulted in an increase of energy consumption of approximately 8.1 × 108 MJ/year due to the fuel use in the MSWI in scenario F. GHG emissions

Figure 3

|

Energy consumption and GHG emissions in each scenario.

Figure 3(b) shows the GHG emissions for each scenario. Initially, the GHG emissions from the MSWI were 6.04 × 104 t-CO2-eq/year for scenario A. This value was equal to 132 kg-CO2-eq/t-waste in the MSW as an emission factor, which was similar to the value reported by Inaba et al. (). The GHG emissions from the WWTP were 4.15 × 104 t-CO2-eq/year in scenario A. This value was equal to 0.284 kg CO2-eq/m3 as an emission factor, which in this study fell within the range of emission factors reported by Fukushima & Somiya () and was considered reasonable. From Figure 3(b), a comparison of scenarios A and B indicates little difference in GHG emissions. Although in

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scenario B, the GHG emissions derived from N2O and fuel consumption from sludge incineration were trivial, decreasing the LHVw of the input waste to the MSWI and increasing its mass resulted in greater electricity and fuel consumption in the MSWI. Comparing scenario A to scenario C, the co-digestion of sewage sludge and kitchen waste reduced GHG emissions by 4.26 × 104 t-CO2-eq/year due to the reduction in electricity and fuel energy consumption due to biogas generation and the lower fuel requirements for a MSWI with co-digestion. However, the introduction of an A2O process to the WWTP increased GHG emissions by approximately 8.9 × 103 t-CO2-eq/year due to a greater electricity usage in scenario E compared to scenario C. The co-digestion of kitchen wastes, sewage sludge and paper wastes and the incineration of dewatered sludge in scenario F resulted in an increase in GHG emissions of approximately 9.1 × 104 t-CO2-eq/year due to the higher fuel consumption in the MSWI compared to scenario C.

CONCLUSIONS In this study, we produced a simulation program that could calculate the mass and heat balance of wastewater and MSW treatment plants when these plants operate separately, or are mutually dependent on mass and energy. Considering the effluent quality, LCC, energy consumption and GHG emissions, scenario D or E would be most desirable. These scenarios treat wastewater from the MSWI in the WWTP with the conventional activated sludge process or the A2O process as a biological treatment, co-digest kitchen wastes and sewage sludge in the WWTP and co-combust dewatered sludge and MSW. When strict water quality controls exist in the effluent destination, scenario E is considered the more desirable scenario. However, the collection of waste was not included in the model. Thus, the actual application of this model requires a more detailed study.

ACKNOWLEDGEMENT This research was financially supported by the Global Centers of Excellence (GCOE) Program entitled ‘Global Center for Education and Research on Human Security Engineering for Asian Megacities’.

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REFERENCES Fukushima, T. & Somiya, I.  The general evaluation on the reduction of environmental load in a sewage treatment plant. J. EICA 15 (2/3), 89–97 (in Japanese). Inaba, R., Nansai, K., Fujii, M. & Hashimoto, S.  Hybrid lifecycle assessment (LCA) of CO2 emission with management alternatives for household food wastes in Japan. Waste Manag. Res. 28 (6), 496–507. Japan Agency for Natural Resources and Energy  Outline of the 2007 Annual Report on Energy, 181 (in Japanese). Available from: www.enecho.meti.go.jp/topics/hakusho/ 2007/2-1.pdf. (Last accessed: 21 October 2013) (in Japanese). Japan Sewage Works Association  Japan Sewage Statistics in 2008 FY. Tokyo, Japan (in Japanese). Japan Sewage Works Association Flow chart of the treatment and utilization amount of sewage sludge in Japan. Available from: www.jswa.jp/data-room/data.html. (Last accessed: 30 November 2012) (in Japanese). Kyoto City, Japan  Project summery of Environmental Policy Bureau, Kyoto City, 85–92 (in Japanese). Available from: www.city.kyoto.lg.jp/kankyo/cmsfiles/contents/0000091/ 91984/6gomisyori.pdf. (Last accessed: 30 November 2012) (in Japanese). Martin, P., Michal, T. & Ladislav, B.  Energy efficient processing of waste. Chem. Eng. Trans. 21, 841–846. Matsuda, A., Ide, T. & Fujii, S.  Behavior of nitrogen and phosphorus during batch aerobic digestion of waste activated sludge – continuous aeration and intermittent aeration by control of DO. Water Res. 22 (12), 1495–1501. Ministry of the Environment, Japan  Statistical Handbook of Waste Treatment in Japan, 1–3 (in Japanese). Available from: www.env.go.jp/recycle/waste_tech/ippan/h21/data/ disposal.pdf. (Last accessed: 30 November 2012) (in Japanese). Ministry of the Environment, Japan  Establishing a Sound Material-Cycle Society, Milestone Toward a Sound Material-Cycle Society Through Changes in Business and Life Styles, 11–57. Available from: www.env.go.jp/en/ recycle/smcs/a-rep/2010gs_full.pdf. (Last accessed: 30 November 2012). Oshita, K., Takaoka, M., Takeda, N. & Matsumoto, T.  Optimization of sludge and wastewater treatment systems: a case study of sewage treatment facilities around Lake Biwa. In: Proceedings of IWA Conference on Management of Residues Emanating from Water and Wastewater Treatment, Johannesburg, South Africa, August 9–12. Shomura, S., Oshita, K., Takaoka, M., Matsumoto, T. & Morisawa, S.  A comparative evaluation of sewage treatment systems from the perspective of energy consumption. In: Proceedings of IWA Sludge Conference 2009, Harbin, China, August 8–11. Soda, S., Arai, T., Inoue, D., Ishigaki, T., Ike, M. & Yamada, M.  Statistical analysis of global warming potential, eutrophication potential, and sludge production of wastewater treatment plants in Japan. J. Sustain. Energy Environ. 4, 33–40.

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Suda, R., Somiya, I., Wakisaka, K. & Yamada, A.  Trend analysis of specific energy consumption at sewage treatment plants. J. Japan Sewage Works Assoc. 45 (10), 107–113 (in Japanese). Takaoka, M., Mizutani, K., Oshita, K. & Mizuno, T.  Effect of energy recovery technologies on reduction of GHG emission from municipal solid waste incinerator. J. EICA 16 (2/3), 12– 21 (in Japanese). The Kansai Electric Power Co., Inc. The electricity prices table for consumers using extra-high voltage at Kansai in Japan

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(www1.kepco.co.jp/yakkan/high_1.html) and The electricity prices table for electric power purchase from renewable energy power generation (biomass power generating). Available from: www1.kepco.co.jp/energy/kaitori/images/ biomass.pdf. (Last accessed: 24 December 2012) (in Japanese). Renou, S., Thomas, J. S., Aoustin, E. & Pons, M. N.  Influence of impact assessment methods in wastewater treatment LCA. J. Clean. Prod. 16, 1098–1105.

First received 8 August 2013; accepted in revised form 20 November 2013. Available online 19 December 2013

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Effect of co-managing organic waste using municipal wastewater and solid waste treatment systems in megacities.

A model was developed to calculate the mass and heat balances of wastewater and municipal solid waste treatment plants when these plants operate eithe...
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