full treatment of landfill leachate by using combined
FULL TREATMENT OF LANDFILL LEACHATE BY USING COMBINED REVERSE OSMOSIS AND SUBMERGED COMBUSTION EVAPORATOR: CASE STUDY D. YUE*, L. ZHANG**, W. ZHANG* * School of Environment, Tsinghua University, Beijing 100084, China ** Key Laboratory for Solid Waste Management and Environment Safety (Tsinghua University), Ministry of Education of China, Beijing 100084, China
SUMMARY: Discharge requirements on landfill leachate are getting more and more stringent. In China, for instance, the leachate must be treated on site and an integrated treatment facility must be built, which is generally more advanced and complicated than that for sewage treatment. Membrane techniques, i.e. nano-filtration (NF) and/or reverse osmosis (RO), which are usually expensive, have to be applied to leachate treatment, and the effluent can meet the discharge limits. With application of membrane filtration technology, the effluent quality can reach a quite high standard, but the pollutants are concentrated in the retention since it is mere a physical separation process. Having accumulated most salinity and pollutants, the treatment of the NF/RO originated retentate has caused remarkable problems. Unfortunately, there are no definite requirements on the retained contaminants within current standards. Some of the concentrate is being transferred to the sewage treatment plants, which means the pollutants are transferred to further treatment following an expensive process of concentration onsite. Submerged combustion evaporation (SCE) is one kind of evaporation process(Yue et al., 2007), in which hot combustion gas bubbles go through the liquid and direct heat-transfer takes place between the hot gases and the liquid without any fixed interface. To remove the volatile organic compounds (VOCs) without additional energy consumption, a two-stage SCE system has been developed, concentrating the NF/RO originated retentate using landfill gas (LFG) as an energy source. This paper introduces a case study of landfill leachate in China. The leachate is treated with a process consisting of membrane bioreactor (MBR), NF, and RO. The retentate of NF and RO was mixed and then sent to the SCE. Both raw leachate and membrane are fully treated. The performance of the entire system is discussed.
1. INTRODUCTION In response to deal with the increasingly serious resource and environmental problems, Chinese government, as the country environment of the public goods providers and protectors, has developed a more stringent leachate discharge standard(He et al., 2015) Facing to the extremely strict standard, a series of combined processes recently came into use in some engineering projects for leachate treatment in China. Bioreactor coupled with membrane techniques and evaporation process, as one of the representatives, were accepted and widely used to dispose leachate and concentrate, respectively. As effective means of method, MBR+NF+RO system for leachate and SCE for the rerentate Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
has been applied for some landfill and incineration in China. This thesis discussed the case located in Haidian district, Beijing, which adopting the above technical proposal and still operated in these days. The purpose of this paper towards the application of full leachate treatment was to describe its basic process flow, principle, and technical characteristics; manifest the performance of the whole process and each unit; and the system was analyzed and explained based on the water balance and energy balance from the influent of the regulation tank to RO and SCE discharge.
2. CASE OVERVIEW In this paper, the treatment center designed to dipose landfill leachate from a municipal solid waste(MSW) landfill in Beijing, has applied the on-site integrated management facility, including Biological wastewater treatment system, Membrane water treatment system, and Evaporation system. The design scale of this landfill was 604000 m2 of area and 4800t of volume, and 600t/d of volume for the center. The effluent of the center was under the Chinese regulation and implemented local standards in Beijing(DB11/307-2013). Basic process flow of entire system was portrayed in Figure 1., Regulation Tank, Anaerobic digestion, Membrane Bioreactor, Nano-filtration (NF), Reverse osmosis (RO) and Submerged combustion evaporation (SCE) units are provided.
Figure 1. Basic process flow of leachate treatment system
Since NF/RO has extensively used, the the interception of pollutants generates a large volume of membrane concentrate, which loaded with mounts of persistent organic compounds and salinity. SCE with design capability of 50m3/d to futher enrich the waste water was adopted in this disposal center and constructed in 2015. Basic process flow of SCE unit was demonstrated in Figure 2.
Figure 2. Basic process flow of SCE unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3. EFFICIENCY OF INDIVIDUAL UNIT AND ENTIRE PROGRESS 3.1 COD degradation efficiency Removal efficiency of COD/NH3-N in entire procedure was made on the basis of amount of operation data collected over a period of time. To manifest the performence in the steady operation stage, we selected steady running data for one month (in February 2017), involving each unit and the whole system (in Figure 3-10). Effluent
Removal Efficiency
18000
0,8
16000
0,7
14000
0,6
12000
0,5
10000
0,4
8000
0,3
6000 4000
0,2
2000
0,1
0
COD(C/C0)
COD(mg/l)
Influent
0 0
5
10
15
20
25
30
Date
Figure 3. COD concentration of influent and effluent in Anaerobic Digestion unit.
Influent
Effluent
Removal Efficiency
6000
0,8 0,7
5000
0,5
3000
0,4 0,3
2000
COD(C/C0)
COD(mg/l)
0,6 4000
0,2 1000
0,1
0
0 0
5
10
15
20
25
30
Date
Figure 4. COD concentration of influent and effluent in Membrane Bioreactor unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Effluent
Removal Efficiency
3000
1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0
COD(mg/l)
2500 2000 1500 1000 500 0 0
5
10
15
20
25
COD(C/C0)
Influent
30
Date
Figure 5. COD concentration of influent and effluent in NF unit.
Influent
Effluent
Removal Efficiency
1200 0,9 0,7
800
0,5
600 400
0,3
200
0,1
0
COD(C/C0)
COD(mg/l)
1000
-0,1 0
5
10
15
20
25
30
Date
Figure 6. COD concentration of influent and effluent in RO unit.
By analysing the removal efficiency of COD in entire procedure, it showed that the reduction occured in every uint and the highest removal rate (more than 90%) achieved in RO unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3.2 Ammonia removal efficiency Effluent
Removal Efficiency
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0
0,07 0,05 0,03 0,01
NH3-N(C/C0)
NH3-N(mg/l)
Influent
-0,01 -0,03 0
5
10
15
20
25
30
Date
Figure 7. Ammonia concentration of influent and effluent in Anaerobic Digestion unit. Influent
Effluent
300
NH3-N(mg/l)
250 200 150 100 50 0 0
5
10
15
20
25
30
Date
Figure 8. Ammonia concentration of influent and effluent in Membrane Bioreactor unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Influent
Effluent
10
15
300
NH3-N(mg/l)
250 200 150 100 50 0 0
5
20
25
30
Date
Figure 9. Ammonia concentration of influent and effluent in NF unit.
Effluent
Removal Efficiency
300
1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0
NH3-N(mg/l)
250 200 150 100 50 0 0
5
10
15
20
25
NH3-N(C/C0)
Influent
30
Date
Figure 10. Ammonia concentration of influent and effluent in RO unit.
By analysing the removal efficiency of ammonia in entire procedure, it showed that the reduction mainly occured in Anaerobic Digestion uint, the removal rate was about 99%. 3.3 Routine index removal efficiency of SCE Removal efficiency of some basic index in SCE was represented on the basis of operation data collected in the steady operation stage (in Table 1).
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Table 1. Basic index of influent concentrate and steam residue. TDS pH TS FDS
Concentrate
Steam residue
33-43 7.1-7.7 35-45 11-15
220-330 8.4-8.8 300-400 40-80
4. WATER BALANCE OF THE INTEGRATED PROCESS The running scale of this center was actually 400m3/d of volume.Therefore, when establishing the water balance model, it was set as the input volume. And the water balance model through the entire procedure presented in Figure 11.
Figure 11. Water balance of the integrated process. AKNOWLEDGEMENTS The authors are grateful for the financial support from the Special Fund of Environmental Protection Research for Public Welfare of China (No. 201509055). REFERENCES He, R., Wei, X.M., Tian, B.H., Su, Y., Lu, Y.L., (2015). Characterization of a joint recirculation of concentrated leachate and leachate to landfills with a microaerobic bioreactor for leachate treatment. Waste management, vol. 46, 380-388. Yue, D., Xu, Y., Mahar, R.B., Liu, F., Nie, Y., (2007). Laboratory-scale experiments applied to the design of a two-stage submerged combustion evaporation system. Waste management, vol. 27, 704-710.
SUMMARY: Discharge requirements on landfill leachate are getting more and more stringent. In China, for instance, the leachate must be treated on site and an integrated treatment facility must be built, which is generally more advanced and complicated than that for sewage treatment. Membrane techniques, i.e. nano-filtration (NF) and/or reverse osmosis (RO), which are usually expensive, have to be applied to leachate treatment, and the effluent can meet the discharge limits. With application of membrane filtration technology, the effluent quality can reach a quite high standard, but the pollutants are concentrated in the retention since it is mere a physical separation process. Having accumulated most salinity and pollutants, the treatment of the NF/RO originated retentate has caused remarkable problems. Unfortunately, there are no definite requirements on the retained contaminants within current standards. Some of the concentrate is being transferred to the sewage treatment plants, which means the pollutants are transferred to further treatment following an expensive process of concentration onsite. Submerged combustion evaporation (SCE) is one kind of evaporation process(Yue et al., 2007), in which hot combustion gas bubbles go through the liquid and direct heat-transfer takes place between the hot gases and the liquid without any fixed interface. To remove the volatile organic compounds (VOCs) without additional energy consumption, a two-stage SCE system has been developed, concentrating the NF/RO originated retentate using landfill gas (LFG) as an energy source. This paper introduces a case study of landfill leachate in China. The leachate is treated with a process consisting of membrane bioreactor (MBR), NF, and RO. The retentate of NF and RO was mixed and then sent to the SCE. Both raw leachate and membrane are fully treated. The performance of the entire system is discussed.
1. INTRODUCTION In response to deal with the increasingly serious resource and environmental problems, Chinese government, as the country environment of the public goods providers and protectors, has developed a more stringent leachate discharge standard(He et al., 2015) Facing to the extremely strict standard, a series of combined processes recently came into use in some engineering projects for leachate treatment in China. Bioreactor coupled with membrane techniques and evaporation process, as one of the representatives, were accepted and widely used to dispose leachate and concentrate, respectively. As effective means of method, MBR+NF+RO system for leachate and SCE for the rerentate Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
has been applied for some landfill and incineration in China. This thesis discussed the case located in Haidian district, Beijing, which adopting the above technical proposal and still operated in these days. The purpose of this paper towards the application of full leachate treatment was to describe its basic process flow, principle, and technical characteristics; manifest the performance of the whole process and each unit; and the system was analyzed and explained based on the water balance and energy balance from the influent of the regulation tank to RO and SCE discharge.
2. CASE OVERVIEW In this paper, the treatment center designed to dipose landfill leachate from a municipal solid waste(MSW) landfill in Beijing, has applied the on-site integrated management facility, including Biological wastewater treatment system, Membrane water treatment system, and Evaporation system. The design scale of this landfill was 604000 m2 of area and 4800t of volume, and 600t/d of volume for the center. The effluent of the center was under the Chinese regulation and implemented local standards in Beijing(DB11/307-2013). Basic process flow of entire system was portrayed in Figure 1., Regulation Tank, Anaerobic digestion, Membrane Bioreactor, Nano-filtration (NF), Reverse osmosis (RO) and Submerged combustion evaporation (SCE) units are provided.
Figure 1. Basic process flow of leachate treatment system
Since NF/RO has extensively used, the the interception of pollutants generates a large volume of membrane concentrate, which loaded with mounts of persistent organic compounds and salinity. SCE with design capability of 50m3/d to futher enrich the waste water was adopted in this disposal center and constructed in 2015. Basic process flow of SCE unit was demonstrated in Figure 2.
Figure 2. Basic process flow of SCE unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3. EFFICIENCY OF INDIVIDUAL UNIT AND ENTIRE PROGRESS 3.1 COD degradation efficiency Removal efficiency of COD/NH3-N in entire procedure was made on the basis of amount of operation data collected over a period of time. To manifest the performence in the steady operation stage, we selected steady running data for one month (in February 2017), involving each unit and the whole system (in Figure 3-10). Effluent
Removal Efficiency
18000
0,8
16000
0,7
14000
0,6
12000
0,5
10000
0,4
8000
0,3
6000 4000
0,2
2000
0,1
0
COD(C/C0)
COD(mg/l)
Influent
0 0
5
10
15
20
25
30
Date
Figure 3. COD concentration of influent and effluent in Anaerobic Digestion unit.
Influent
Effluent
Removal Efficiency
6000
0,8 0,7
5000
0,5
3000
0,4 0,3
2000
COD(C/C0)
COD(mg/l)
0,6 4000
0,2 1000
0,1
0
0 0
5
10
15
20
25
30
Date
Figure 4. COD concentration of influent and effluent in Membrane Bioreactor unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Effluent
Removal Efficiency
3000
1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0
COD(mg/l)
2500 2000 1500 1000 500 0 0
5
10
15
20
25
COD(C/C0)
Influent
30
Date
Figure 5. COD concentration of influent and effluent in NF unit.
Influent
Effluent
Removal Efficiency
1200 0,9 0,7
800
0,5
600 400
0,3
200
0,1
0
COD(C/C0)
COD(mg/l)
1000
-0,1 0
5
10
15
20
25
30
Date
Figure 6. COD concentration of influent and effluent in RO unit.
By analysing the removal efficiency of COD in entire procedure, it showed that the reduction occured in every uint and the highest removal rate (more than 90%) achieved in RO unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3.2 Ammonia removal efficiency Effluent
Removal Efficiency
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0
0,07 0,05 0,03 0,01
NH3-N(C/C0)
NH3-N(mg/l)
Influent
-0,01 -0,03 0
5
10
15
20
25
30
Date
Figure 7. Ammonia concentration of influent and effluent in Anaerobic Digestion unit. Influent
Effluent
300
NH3-N(mg/l)
250 200 150 100 50 0 0
5
10
15
20
25
30
Date
Figure 8. Ammonia concentration of influent and effluent in Membrane Bioreactor unit.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Influent
Effluent
10
15
300
NH3-N(mg/l)
250 200 150 100 50 0 0
5
20
25
30
Date
Figure 9. Ammonia concentration of influent and effluent in NF unit.
Effluent
Removal Efficiency
300
1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0
NH3-N(mg/l)
250 200 150 100 50 0 0
5
10
15
20
25
NH3-N(C/C0)
Influent
30
Date
Figure 10. Ammonia concentration of influent and effluent in RO unit.
By analysing the removal efficiency of ammonia in entire procedure, it showed that the reduction mainly occured in Anaerobic Digestion uint, the removal rate was about 99%. 3.3 Routine index removal efficiency of SCE Removal efficiency of some basic index in SCE was represented on the basis of operation data collected in the steady operation stage (in Table 1).
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Table 1. Basic index of influent concentrate and steam residue. TDS pH TS FDS
Concentrate
Steam residue
33-43 7.1-7.7 35-45 11-15
220-330 8.4-8.8 300-400 40-80
4. WATER BALANCE OF THE INTEGRATED PROCESS The running scale of this center was actually 400m3/d of volume.Therefore, when establishing the water balance model, it was set as the input volume. And the water balance model through the entire procedure presented in Figure 11.
Figure 11. Water balance of the integrated process. AKNOWLEDGEMENTS The authors are grateful for the financial support from the Special Fund of Environmental Protection Research for Public Welfare of China (No. 201509055). REFERENCES He, R., Wei, X.M., Tian, B.H., Su, Y., Lu, Y.L., (2015). Characterization of a joint recirculation of concentrated leachate and leachate to landfills with a microaerobic bioreactor for leachate treatment. Waste management, vol. 46, 380-388. Yue, D., Xu, Y., Mahar, R.B., Liu, F., Nie, Y., (2007). Laboratory-scale experiments applied to the design of a two-stage submerged combustion evaporation system. Waste management, vol. 27, 704-710.
