알칼리/오존 병합전처리 기법을 이용한 슬러지 감량화 및 재이용 = Sludge Reduction and Reuse with Combined Use of Alkali and Ozone

다국어 초록 (Multilingual Abstract)

This study suggests the process for sludge reduction using a combined pretreatment of alkali and ozone and crystallization techniques for removing and recovering the ammonium and ortho phosphate ion from the solubilized sludge as struvite and apatite. Also, this process can supply the solubilized sludge as an external carbon source into the biological nutrient removal process to improve the water quality of effluent.
There are three stages to achieve the above objective. The first step is to investigate the lab-scale pretreatment processes for sludge reduction and solubilization under the batch operation. The artificial wastewater was used to evaluate the factors affecting crystallization of struvite and apatite. Also, the products(solubilized sludge) of the pretreatment processes were examined as an external carbon source for the biological nutrient removal process using the NUR(nitrate utilization rate) test. The second step is to investigate the pilot-scale pretreatment processes for sludge reduction and solubilization connected with KSMBR(K-water, Ssangyong and KMS membrane bio-reactor) under the continuous-flow operation. The pilot test was carried out to find an optimal condition for improving the efficiencies of crystallization of struvite and apatite in the real excess sludge. Based on the results of previous study, in the third step, a full scale operation of the process for sludge reduction was implemented. The P release reactor and fermenter were added to improve the crystallizing efficiency in front of the process, while KSMBR was installed to guarantee the effluent water quality in the rear of the process. Through the continuous operation, the feasibility and the stability of proposed process were evaluated.
In the first step of this study, the combined pretreatment method of alkali and ozone(pH 11 + 0.32 gO3/gSS) showed highest efficiency of sludge reduction and solubility among the combined pretreatment methods except combined pretreatment of alkali and ozone(pH 11 + 0.32 gO3/gSS + pH 11). Using this combined pretreatment method, 35.6% of reduction efficiency(TSS), 41.8% of solubilization efficiency, 73.5% of rbCOD(readily biodegradable COD) and 6.5 mgNO3--Ng/MLVSS․hr of SDNR(specific denitrification rate) were achieved. Consequently, combined pretreatment of alkali and ozone(pH 11 + 0.32 gO3/gSS) was selected, as it had been relatively high reduction and solubilization efficiency and optimum method for the continuous-flow operation. Struvite was effectively crystallized at the molar ratio of 1.4:1:1(Mg2+:NH4+:PO43-) and pH of 9.6. Apatite was effectively crystallized at the molar ratio of 1:1(Ca2+:PO43-) and over pH of 8.9.
In the second step of this study, when the P release reactor was added in front of the process for sludge reduction, the concentration of AHP(acid hydrolyzable phosphorus) was slightly reduced, while the concentration of PO43- in STP(soluble TP) was dramatically increased. When the fermenter was added in front of the process for sludge reduction, VFA(volatile fatty acid) concentration in SCOD of solubilized sludge was increased by 2 times. In addition, when KSMBR of 5 m3/d was installed and connected with the process for sludge reduction, the removal efficiency of the total nitrogen was improved up to 60%. In the case of crystallization, struvite was not properly formated with the solubilized sludge. However, apatite was effectively crystallized at the molar ratio of 4:1(Ca2+:PO43-) and pH of 9.6 ～ 10.0. Through the apatite crystallization, 94.3% of PO43- was removed from the solubilized sludge. At a feasibility test for the sludge solubilized as a fertilizer, struvite and apatite crystallized from the excess sludge of KSMBR process, D city and J county fell short of the salinity standard of the Rural Development Administration and Ministry of Environment. On the other hand, they met the standards in terms of all other heavy metals. As the struvite and apatite obtained from KSMBR had about 30 % of P2O5, they can be considered as a raw material for phosphorous fertilizer.
In the last step, when the full scale process for sludge reduction was continuously operated for 5 months, the average efficiencies of sludge reduction and solubility were 35% and 20.4%, respectively. When the KSMBR process was connected in the rear of the process for sludge reduction, the removal efficiency of the total phosphorus was improved up to 40%. In the result of economic feasibility analysis, the cost of operating and maintenance on the process for sludge reduction was 12,550 KRW(Korea Won)/㎥. At the 4,654 KRW/㎥ of dewatering cost and more than 55,500 KRW/㎥ of incineration cost, KSMBR process-process for sludge reduction-mechanical dewatering-incineration is more economical than BNR(biological nutrient removal) process-mechanical dewatering-incineration. Therefore, the suggested process for sludge reduction would have competitive price for the effective sludge treatment.

목차 (Table of Contents)

• 제 Ⅰ 장. 서론 1
• 1.1 연구배경 1
• 1.2 연구의 목적 및 내용 3
• 1.3 참고문헌 5
• 제 Ⅱ 장. 문헌고찰 7
• 2.1 하수슬러지 발생 및 처리현황 7
• ⑴ 국내 하수슬러지 발생 및 처리현황 7
• ⑵ 국외 하수슬러지 처리현황 10
• 2.2 하수슬러지 특성 11
• 2.3 하수슬러지 처리제도 및 정책 15
• ⑴ 런던협약 96 의정서 15
• ⑵ 국내 하수슬러지 처리제도 및 정책 16
• 2.4 슬러지 전처리 기법 21
• ⑴ 열 전처리 22
• ⑵ 기계적 전처리 23
• ⑶ 마이크로파 전처리 24
• ⑷ 초음파 전처리 24
• ⑸ 화학적 전처리 25
• ⑹ 오존 전처리 27
• 2.5 결정화 기법 32
• ⑴ Struvite 및 apatite의 물리 화학적 성질 32
• ⑵ Struvite chemistry 34
• ⑶ Apatite chemistry 37
• ⑷ Struvite 생성에 미치는 영향인자 38
• ⑸ Apatite 생성에 미치는 영향인자 39
• ⑹ 비료로서의 재이용(Struvite 및 apatite) 40
• 2.6 국내외 감량화 기술 45
• ⑴ ATAD(Auto thermal aerobic digestion) 45
• ⑵ Biolysis O 46
• ⑶ 하수슬러지를 오존으로 분해시켜 잉여슬러지의 배출을 감량화한 기술 47
• ⑷ 오존처리 및 가성소다를 이용하여 슬러지를 분해시키고 호기성소화 및
• 침지식 평막을 결합한 하수슬러지 저감기술 48
• ⑸ Lysozyme 분비세균을 이용한 잉여슬러지 감량형 하수 고도처리 기술 49
• 2.7 참고문헌 51
• 제 Ⅲ 장. 병합전처리를 이용한 감량화/가용화 효율평가 및 결정화 영향인자 평가(회분식 연구) 61
• 3.1 서론 61
• 3.2 실험재료 및 방법 63
• ⑴ 병합전처리를 이용한 감량화 및 가용화 효율평가 63
• ⑵ 전처리된 슬러지의 외부탄소원으로 활용 가능성 평가 67
• ⑶ 결정화 영향인자 평가 70
• 3.3 실험결과 및 고찰 71
• ⑴ 병합전처리를 이용한 감량화 및 가용화 효율평가 71
• ⑵ 외부탄소원으로 활용 가능성 평가 75
• ⑶ 결정화 영향인자 평가 79
• ⑷ 슬러지 감량화 공정 제안 94
• 3.4 결론 96
• 3.5 참고문헌 98
• 제 Ⅳ 장. 슬러지 감량형 하수 고도처리 공정 연구(Pilot plant 연구) 103
• 4.1 서론 103
• 4.2 실험재료 및 방법 104
• ⑴ 전처리 시스템의 최적화 및 감량화/가용화 효율평가 104
• ⑵ 감량화 공정의 구성 및 개선 108
• ⑶ 가용화 슬러지에서 결정화를 위한 약품주입량 평가 및 결정물질의 비료 활용 가능성 평가 113
• 4.3 실험결과 및 고찰 116
• ⑴ 전처리 시스템의 최적화 및 감량화/가용화 효율평가 116
• ⑵ 감량화 공정의 구성 및 개선 123
• ⑶ 가용화 슬러지에서 결정화를 위한 약품주입량 평가 및 결정물질의 비료 활용 가능성 평가 136
• ⑷ 실증플랜트 설계 144
• 4.4 결론 146
• 4.5 참고문헌 148
• 제 Ⅴ 장. 슬러지 감량형 하수 고도처리 공정의 실증플랜트 연구 152
• 5.1 서론 152
• 5.2 실험재료 및 방법 153
• ⑴ 실험재료 및 장치 153
• ⑵ 실험방법 161
• 5.3 실험결과 164
• ⑴ 인용출조에서 인 방출 164
• ⑵ 알칼리 및 오존 동시 전처리에 의한 감량화 및 가용화 165
• ⑶ 발효농축조에서의 고액분리/유기산 생성 및 질소거동 166
• ⑷ 결정화 침전조에서의 apatite 생성을 통한 인 제거 168
• ⑸ 슬러지 감량화 공정과 KSMBR공정의 연계 운전 172
• ⑹ 슬러지 감량화 공정의 운영비 분석 및 경제성 검토 179
• 5.4 결론 186
• 5.5 참고문헌 187
• 제 Ⅵ 장. 종합결론 189