The object of this study is to feasibility assesment for co-digestion efficiency of food waste recycling wastewater(FWR) with thermal hydrolysis process dehydration cake (THP Sludge). As a result of THP pre-treatment experimental conditions to 160oC and 30 minutes, the solubility rate(conversion rate of TCOD to SCOD) of the THP sludge increased by 34%. And the bio-methane potential in the THP sludge increased by about 1.42 times from 0.230 to 0.328 m3 CH4/kg VS compared to the non-pre-treatment. The substrates of the co-digestion reactor were FWR and THP sludge at a 1:1 ratio. Whereas, only FWR was used as a substrate in the digestion reactor as a control group. The experimental conditions are 28.5 days of hydraulic retention time(HRT) and 3.5 kg VS/m3-day of organic loading rate(OLR). During the 120 days operation period, the co-digestion reactor was able to operate stably in terms of water quality and methane production, but the FWR digestion reactor deteriorated after 90 days, and methane production decreased to 0.233 m3 CH4/kg VS, which is 67% of normal condition. After 120 days of the experiment, organic loading rate(OLR) of co-digestion reactor was gradually increased to 4.5 kg VS/m3-day and operated for 80 days. Methane production during 80 days was evaluated to be good at the level of 0.349 m3 CH4/kg VS. As a result of evaluating the dehydration efficiency of the sludge before/after 150-180oC THP using a filter press, it was confirmed that the moisture content of the sludge treated before THP at 180oC was 75% and improved by 8% from 83-85% level. Therefore, it is expected that the co-digestion reactor of FWR and THP sludge will ensure stable treatment water quality and increase bio-methane production and reduction effect of dehydration sludge volume.

The performance of the new aerobic digestion system combined with inorganic sludge separation unit and sludge solubilization unit, CaviTec II, is evaluated. Anaerobic digester effluent sludge is used for feed sludge of CaviTec II system. By addition of CaviTec II, the amount of cake generated is reduced by 27%, and the soluble nitrogen is reduced by 92%.

Laboratory experiments were conducted to investigate the effect of digestion temperature on the settleability and dewaterability of anaerobically digested sludge. The digesters were operated at a hydraulic retention time of 20 days with a loading rate of 0.63~0.66kg volatile solids per cubic meter per day at the temperature of $35^{\circ}C$ and $55^{\circ}C$. A mixed primary and secondary municipal sludge was used as a feed. The interface height of the sludge during settling test was recorded to identify settleability. As a measure of dewaterability of the sludge, specific resistance and capillary suction time were also measured with and without chemical conditioning. Higher digestion efficiency was obtained at $55^{\circ}C$ than $35^{\circ}C$. However, the settleability and dewaterability of the sludge at $35^{\circ}C$ were quite higher than those of the sludge digested at $55^{\circ}C$. The optimum dosages of ferric chloride for sludge conditioning were 0.4% and 0.6% at $35^{\circ}C$ and $55^{\circ}C$, respectively. The filtrate COD of the sludge digested at $55^{\circ}C$ was higher than at $35^{\circ}C$, which means that poor dewaterability of the sludge result in high filtrate COD.

This study evaluated the biochemical methane potential (BMP) of primary sludge, secondary sludge, and food waste in batch anaerobic mono-digestion tests, and investigated the effects of mixture ratio of those organic wastes on methane yield and production rate in batch anaerobic co-digestion tests, that were designed based on a simplex mixture design method. The BMP of primary sludge, secondary sludge and food waste were determined as 234.2, 172.7, and 379.1 mL CH4/g COD, respectively. The relationships between the mixing ratio of those organic wastes with methane yield and methane production rate were successfully expressed in special cubic models. Both methane yield and methane production rate were estimated as higher when the mixture ratio of food waste was higher. At a mixing ratio of 0.5 and 0.5 for primary sludge and food waste, the methane yield of 297.9 mL CH4/g COD was expected; this was 19.4% higher than that obtained at a mixing ratio of 0.3333, 0.3333 and 0.3333 for primary sludge, secondary sludge, and food waste (249.5 mL CH4/g COD). These findings could be useful when designing field-scale anaerobic digersters for mono- and co-digestion of sewage sludges and food waste.

This study was performed to test the feasibility of thermophilic (55oC) co-digestion of municipal sewage sludge and food wastes. The management variables of co-digestion were the mixed ratios of municipal sewage sludge and food waste hydraulic retention times (HRTs). During the operation of thermophilic co-digestion, the reactor pH ranged from 7.0 to 7.5 and the reactor alkalinity remained above 3,200 to 4,000 mg/L as CaCO3. The volatile fatty acids concentration increased as the HRT shortened from 20 days to 10 days and the mixture ratio increased to 1:4, but did not reach toxic levels for co-digestion of sewage sludge and food wastes. Methane productivity increased gradually as the organic loading rate increased. Maximum methane productivity reached 1.03v/v-d at an HRT of 10 days and at the mixture ratio of 1:4. The TVS removal efficiency decreased from 70.6% to 58.3% as the HRT shortened from 20 days to 10 days. TVS removal efficiency ranged from 57.0% to 77% during the entire operation. It is likely that thermophilic co-digestion of sewage sludge and food wastes is a very effective method both to environmentally treat food waste and to economically produce gas for energy.

하수처리과정에서 발생하는 슬러지의 부피를 줄이는 동시에 이들의 유기물 성분을 메탄 등의 바이오가스로 전환하기 위해 중온(35℃)에서의 혐기소화 공정이 널리 적용되고 있다. 혐기소화공정의 안정성이나 에너지 투입량 측면에서는 중온혐기소화가 적합하다고 알려져 있지만, 높은 유기물 부하량(organic loading rate, OLR)을 처리하기 위해 반응속도를 상승시키거나 SRT(sludge retention time)을 줄이기 위해 고온(55℃) 혐기소화를 적용하기도 한다. 고온 혐기소화공정을 새롭게 시작할 때 접종물을 기존의 고온 혐기소화공정으로부터 얻기 힘든 경우 중온혐기소화액을 고온에서 적응시켜 접종하기도 한다. 이때 온도를 적응시키는 방법에 따라 공정 효율이 달라지는데, 연구에서는 중온혐기소화액으로부터 고온 혐기소화 접종물을 제작하기 위한 방법으로 온도를 올리는 방법을 달리하였을 때 이들의 메탄 생산과 미생물 군집에 미치는 영향을 살펴보고자 하였다. 본 연구수행을 위해 광주 제 1 하수처리장에서 중온혐기소화액, 1, 2차 농축 슬러지 등을 샘플링 하여 두 대의 반응기(Working volume : 3L)를 설치하여 회분식(Batch)운전 후 연속교반탱크형반응기(CSTR)로 운전(SRT 20, 40일)하였다. 먼저 한 대의 반응기는 35℃에서 55℃로 한 번에 온도변화를 주었고, 다른 반응기의 경우에는 35℃에서 하루에 1도씩 올려서 약 20일에 걸쳐 55℃로 올린 뒤 55℃로 유지하였다. 반응기의 효율을 확인하기 위해 메탄 발생량, total solids (TS), volatile solids (VS), total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD), soluble components (protein, carbohydrate), pH 등을 측정하였으며, NGS (next generation sequencing)를 활용하여 혐기소화 전/후의 소화액의 미생물 군집변화를 알아보았다.

하수처리시설의 방류수 수질기준은 계속적으로 강화되고 있으며, 이러한 기준을 충족시키기 위해 다양한 공법을 적용하려는 노력들이 증가하고 있다. 지금까지는 질소, 인 처리를 목적으로 활성슬러지 공법을 많이 적용해왔지만, 활성슬러지 공법의 경우 용존산소 및 온도 유지, 미생물의 생장에 필요한 탄소원이 부족할 경우 추가적인 메탄올 공급의 필요 등과 같은 문제점들을 가지고 있어 대안책이 필요한 상황이다. 따라서 본 연구에서는 응집제 주입을 통해 유기물 뿐만 아니라 질소, 인 등을 제거하여 활성슬러지 공법을 대체할 수 있는 응집-침전 1차 처리(Chemically enhanced primary treatment, CEPT)의 최적화 과정을 진행하였으며, 추가적으로 CEPT 슬러지를 이용하여 혐기성 소화를 진행하였을 때 메탄 생성효율에는 어떠한 영향을 미치는지 확인하고자 하였다. 먼저 문헌조사를 통해 총 7개의 후보군(FeCl2, FeCl3, FeSO4, PACl, Al2(SO4)3, 키토산, glucan)을 선정하였으며, jar-test를 통해 응집제로써의 적용가능성 및 최적 주입량을 확인하였다. Jar-test의 경우 광주 제 1하수처리장으로 들어오는 하수 원수 500ml를 이용하여 진행하였으며, 급속교반(150rpm, 1분), 완속교반(40rpm, 10분), 침전(10분) 순으로 진행한 뒤 상징액을 통해 저감효과를 확인하였다. 90% 이상의 탁도 저감효과를 보인 FeCl3, PACl, Al2(SO4)3 대상으로 CEPT 슬러지를 제작하여 혐기성 소화를 진행하였다. jar-test에서는 PACl이 응집제 주입량 대비 가장 높은 탁도저감효과를 보인 반면, 혐기성 소화 공정에서는 PACl을 이용하여 제작한 CEPT 슬러지의 메탄 발생효율이 가장 낮고, FeCl3를 주입한 경우에 가장 메탄발생효율이 높은 것으로 나타났다. 이러한 결과는 PACl의 Al 성분이 미생물의 생장을 저해한 반면, FeCl3의 경우에는 Fe3+가 Fe2+로 환원되는 과정에서 유기물로부터 H+를 받아 유기물의 분해속도를 촉진시켰기 때문인 것으로 추측된다.

Methanogenic community shift and comparison were determined by 454 pryosequencing for two different full-scale anaerobic digesters treating municipal sludge. For monitoring long-term of microbial communities, samples were collected for two year at three-monthly basis. The two mesophilic AD bioreactor were operated at similar operating conditions, but different substrate streams. Methanospirillum were identified as the key drivers of methanogenesis in full-scale anaerobic digester treating municipal sludge. In Joongrang (JR) digester, Methanospirillum was dominant (48%±10.3) over almost all period, but the dominant genus move to Methanosaeta and Methanoculleus due to low acetate concentration (0.02 g/L), total ammonia nitrogen concentration, respectively. In Asan digester (AS), Methanospirillum also was dominant (41%±12.6) like JR digester, but methanogenic community shift was examined twice. One of those was from Methanospirillum to Methanophaerula due to pH sharply decrease (<5.5) and second shift was Methanosaeta increase due to low VFAs concentration (0.25 g/L).

According to the elementary analysis on organic wastes, the C/N ratio, a major condition for anaerobic digestion, is 5.40 to 9.23, except for food waste leachate (FWL). Defined by Tchobanoglous’ mathematical biogas prediction model, methane gas and biogas productions increased, depending on the mixing rate of FWL. Furthermore, anaerobic digestion both wastewater sludge and food waste leachate based on the right mixing ratio, increases methane gas productions compared to digesting wastewater sludge alone. In other words, co-anaerobic digestion is more likely to realize biogasification than single anaerobic digestion. We mix food waste leachate and wastewater sludge from the dairy and beer manufacturing industry by the proportion of 1 : 9, 3 : 7 and 5 : 5. It turns out that they produced 118, 175 and 223 CH4 mL/g VS in the dairy manufacturing and 176, 233 and 263 CH4 mL/g VS in beer manufacturing of methane gas. The result suggests that as the mixing rate of food waste leachate rises, the methane gas productions increases as well. And more methane gas is made when co-digesting wastewater sludge and food waste leachate based on the mixing ratio, rather than digesting only wastewater sludge alone. Modified Gompertz and Exponential Model describe the BMP test results that show how methane gas are produced from organic waste. According to the test, higher the mixing rate of food waste leachate is, higher the methane gas productions is. The mixing ratio of food waste leachate that produces the largest volume of methane gas is 1 : 9 for the dairy industries and 3 : 7 for brewery. Modified Gompertz model and Exponential model describe the test results very well. The correlation values (R2) that show how the results of model prediction and experiment are close is 0.920 to 0.996.

In this study the effects of co-digestion of sewage sludge and food waste leachate on the anaerobic digestion efficiencyfrom sewage treatment facilities in S. Korea were investigated. For this study 15 facilities were selected including 9facilities treating sewage sludge only (S-Only) and 6 facilities treating sewage sludge and food waste leachate (S-MIX).The average volatile solid (VS) removal rate of S-Only was 30.7% and that of S-MIX was 45.2%. The COD removalrate of S-MIX (61.3%) was higher than that of S-Only (48.6%). It has been observed that the anaerobic digestion efficiencyof S-MIX was superior to that of S-Only because S-MIX contained more sufficient nutrient with higher VS contents andtotal solid (TS) contents emerging from food waste leachate. Therefore food waste leachate addition in sewage sludgeanaerobic digestion would be the preferred option to treat only sewage sludge.

The objectives of this research was to evaluate the anaerobic digestibility of waste activated sludge (herein after WAS)and waste beverages (herein after WB) in beverages manufacturing industry using actual plant under various conditions.In this study, anaerobic digestion with WAS and WB were evaluated according to different operating conditions. As thebasis operating conditions for anaerobic digestion, the reaction temperature was controlled at 35 and hydraulic retentiontime 30 days. WAS and WB were mixed at the ratio of 1:0, 9:1, 8:2, 7:3, 5:5, Respectively. The organic loadingrate (herein after OLR) was maintained less than 0.5kgVS/m3·day. Biogas productivity in accordance with VS was fedat the each mixing ratio with WAS and WB was increased from 0.92Nm3/kg VSfeed to 1.28Nm3/kg VSfeed, except mixingratio 5:5 (0.19Nm3/kg VSfeed). Also Biogas productivity in accordance with VS was removed at the each mixing ratiowith WAS and WB was increased from 1.13Nm3/kg VSrem to 1.81Nm3/kg VSrem, except mixing ratio 5:5 (0.35Nm3/kg VSrem). It was judged that pH was reduced with WB addition. From the results, it was judged that anaerobic digestionusing WAS and WB could be feasible.

The objectives of this research was to evaluate the anaerobic digestibility of waste actizvated sludge (WAS) and wastebeverages in beverages manufacturing industry using BMP test under various conditions. Also, the effects of physical(ultrasonic) and biological (lactobacillus) solubilization process on anaerobic digestibility of WAS were thoroughlystudied. The soluble chemical oxygen demand (SCODCr)/total chemical oxygen demand (TCODCr) ratio of WAS was 0.15but the SCODCr/TCODCr ratio after solubilization was increased 17.5% by ultrasonic, 18.8% by lactobacillus respectively.The results of BMP test, methane gas productivity as mixing ratio of WAS and waste beverages were 156ml CH4/gCODCr,164ml CH4/gCODCr and 182ml CH4/g CODCr, respectively 9:1, 8:2, 7:3 before the solubilization of WAS. As themixing ratio of waste beverages increase, VFAs concentration and methane productivity was increased. Also, methanegas productivity as mixing ratio after the solubilization of WAS using ultrasonic and lactobacillus was increased3.3~11.3%, 11.1~15.2% respectively. From the results, it was judged that anaerobic digestion using WAS and wastebeverages could be feasible.

This study has cross checked the change of internal sludge-recycle in Anaerobic-Digestion, and researched about not only the improvement of Bio-gas production from the digested sludge but also the efficient method of sludge minimization. Ultimate object of the study is to reduce the amount of sludge by the improved efficiency of contact with the organic-matter and the microbes in Anaerobic-Digestion. The sludge-recycle fluidized sludge layer and raised the activity of the sludge, the optimal sludge-recycle ratio, VS and COD removal ratio were 1,000%, 28.2% and 27.7%, respectively. Through these results of this study, it may be of use to treat waste sludge by the sludge-recycle ratio in terms of minimization and circulation of resources.

The purpose of this study was to improve low digestibility in anaerobic digestion facility of the sewage treatment plant. To perform this research, sludge digestion and digestion gas purification facilities in sewage treatment plant was applied. In the result of this study, it was very effective for sludge reduction from the improvement of digestive efficiency. In addition, it was confirmed that high purity CH4 (methane) was produced. This results can be useful as basic data to improve the low digestibility in anaerobic digestion processes.

In this study, the effect of hydrogen peroxide (H2O2) pre-treatment for sewage sludge prior to anaerobic digestion wasassessed using a batch test with an objective to decrease nitrogen, dissolved sulfide and siloxane in sewage sludge. Atotal of 6 sets of experiments (Blank, 20, 40, 60, 80 and 100g H2O2/kg wet sludge) were carried out, each with duplicates.To assess the effect of different dosages of H2O2 on anaerobic digestion, the treated sewage sludge was used for biochemical methane potential (BMP) test and SCODcr concentration. Due to the H2O2 pre-treatment, solubilization of SCODcr in pretreated sludge increased by 89% compared to raw sewage sludge, whereas T-N and NH3-N concentrationdecreased. Cumulative methane yields were increased for all pretreated samples due to increased sludge solubilizationthrough H2O2 pre-treatment. In addition, dissolved siloxane concnetrations were decreased for all pretreated samples. Thus,a reduction in dissolved siloxane concenrtation can decrease the siloxane generation potential of sludge during anaerobicdigestion. However, dissolved sulfide concentration remained same. Although H2O2 dosage did not show any furtherimpact on dissolved sulfide, they have significantly decreased T-N, NH3-N and dissolve siloxane concentrations beforeanaerobic digestion.

Waste activated sludge (WAS) and food waste (FW) are available year round at low cost and have the potential to promote synergism in anaerobic digestion (AD). The goal of this study was to clarify the synergism in co-digestion of WAS and FW. A slight amount of FW at various ratios was added to WAS as an auxiliary substrate, and anaerobic batch tests were performed under mesophilic conditions. By adding FW, total CH₄ produced was increased, where most of them were come from WAS, clearly suggesting synergism. Also, lag period was shortened and CH₄ production rate was increased by FW addition. It was hypothesized that enhanced performance was owing to the facilitated hydrolysis of WAS by FW addition, which was revealed by the increased activities of hydrolytic α-amylase and protease.

In this study, anaerobic co-digestion experiments for mixtures consisting of sewage sludge with food wastewater and livestock wastewater were conducted to assess the methane yields, the volatile solids (VS) removal rates and the dynamic kinetics. An augmented simplex centroid design (ASCD) was employed to design the mixing rate of organic wastes for the anaerobic co-digestion. Also, synergistic effects on the anaerobic co-digestion were studied using models obtained by the ASCD. As a result, synergistic effects were not observed in terms of methane yield and VS removal rate. It was just showed that there was a linear relationship between the cumulative methane yield and the mixing rate of food wastewater. The results might be attributable that the sewage sludge and the livestock wastewater had very lower C/N ratio compared with food wastewater that had a C/N ratio within a range required for a correctly operating anaerobic co-digestion. Therefore, increasing mixing rates of food wastewater increased the methane yield and VS removal rate, but there was not a synergistic effect by the anaerobic co-digestion.