The purpose of this study is to investigate the characteristics and performance of nitrogen and phosphorus removal system, Daewoo Nutrients Removal(DNR) system, and to find out the operating parameter for the system. During the study, $10m^3$ pilot plant was operated for the demonstration experiment and the primary effluent was taken from K domestic sewage treatment plant. The TN in the influent had been removed to approximately 70% through the nitrfication in the oxic tank and the denitrfication in the anoxic tank and the $PO_4-P$ and TP in the influent had been removed to 85% and 83% through anaerobic reaction and oxic reaction. The BOD and SS removal rate were 85 to 95% through the system. As the results, the values of effluent BOD, SS and slouble phosphorus were lower than A/O and $A^2/O$ processes. The SPRR (specific phosphorus release rate) at the anaerobic state of DNR system was ranged from 2.2 to 2.6mg SP/g VSS/h. The nutrient removal efficieny of the DNR system in view of the characteristics of the domestic sewage was higher than the pre-established A/O and $A^2/O$ processes. Finally, we believe that the DNR system was superior to the processes deveolped recently.

The feasibility study of using converter slag as a solidifying agent of digested sewage sludge cake has been performed. The availability of converter slag as solidifying agent has been investigated by several trial tests. Based on the trial test results, the optimum mixing ratios of sludge cake and solidification additive are estabilished. Finally the solidification characters of sludge cake are elucidated by SEM and EDS. It is ascertained that converter slag with a small amount of quicklime enhences the solidification. From the result of pH test, overall pH of specimens tends to decrease slowly with curing time. After solidifying specimens had been cured for 7 days, these are water-cured for 24 hours. The weight and strength of all the specimens are nearly the same regardless of the mixed ratios of solidifying agent. The result of leaching tests for four heavy metal ions, Cd, $Cr^{6+}$, Pb and Cu show that the leaching strength becomes below the decision criteria of the specific wastes, respectively. The SEM observation of the delicate structure shows that needlelike crystals appear after solidification which are not observed before. From the EDS analysis, it is found that the main ingredients of needlelike crystals are Ca, Si, Al and O.

연못시스템의 처리정도는 기후조건(氣候條件)과 아주 밀접한 관계가 있다. 기존시스템이 없는 경우 비슷한 기후권의 사례지역을 반드시 비교분석하게 된다. 미국 온대권에 위치한 Corinne과 Eudora 시스템의 기온과 태양복사량을 김포지역과 비교한 결과 아주 유사함이 규명되었다. 특히 태양복사열의 경우, 여름철에 김포지역이 두 시스템보다 조류성장에 유리한 조건이다. 국내 중부지방에 Corinne과 Eudora 시스템과 비슷한 연못시스템을 설치운영(設置運營)하는 데는 문제점이 없음을 알 수 있다. 남부지방은 연중기온이 김포지역보다 높으므로 연못시스템의 이용이 김포지역보다 유리하다. 미국에서는 연못시스템이 2차처리시설(次處理施設)로 합법화되어 있으며, 2차처리 수질기준(水質基準)을 충족시키고 있다. Corinne과 Eudora 연못시스템의 처리수준을 분석한 결과 처리수의 $BOD_5$ 가 30mg/l 이하로 처리되고 있으나, SS 농도가 30mg/l 보다 다소 높은 경우가 있다. Eudora시스템에서 4월에 일어나는 연못하수의 회전기간(回轉期間)을 제외하고는 연못시스템에 적용하는 처리수의 SS기준인 70-100mg/l 이내로 처리되고 있다. 우리나라 중부지방에 Corinne과 Eudora 시스템과 유사한 연못처리시스템을 설치(設置)하면 2차 처리수준으로 하수를 처리할 수 있을 것으로 판단된다. 연못시스템은 양어, 작물생산, 레크레이션이용과 결합시킬 수 있어, 국내의 경우 농촌소도시 지역, 도시경계 생산녹지지역, 내륙 및 하구의 저습지(wetland)에서 소형뿐아니라 대형 시스템으로 활용이 가능하다.

The dewatering characteristics of the sewage sludge was investigated through the experimental observations and model simulations. The activated sludge and the anaerobically digested sludge were examined for the dewaterability evaluation within the pressure range of $0{\sim}10^6N/m^2$. Modified Buchner funnel test and compression test by the consolidometer were conducted to evaluate average specific resistance, porosity, and moisture percentage of filter cake. Shirato's technique of compression-permeability test was followed for the pressure range lower than about $10^2N/m^2$. The flocculation effects on sludge dewatering was also examined for ferric chloride and polymeric flocculant. The application of hydrated lime which can be used for flue-gas desulfurization showed improved moisture percentage, and was thought to have positive feasibility in combined system of sludge dewatering and incineration. Determined characteristic constants were applied to Tiller's cake filtration model to simulate liquid pressure distribution and porosity distribution in cake. Model simulations showed a sharp drop of the porosity close to the cake-medium interface for the highly compressible material such as the activated sludge and the anaerobically digested sludge.

The depth of sewers in residential complexes was determined to prevent the separated sewers from misconnection between storm sewer and sanitary sewer, and from the submersion of the basement by minimizing the phenomenon of backwater when it rains. In residential complexes, main causes of the submersion were the misconnection of sewers, rising of the backwater level at outfall in sewer system, poor maintenance of sewers, and lacking in their cross section. Minimum depth of sewers should be over 1.2~1.5m. According to the economic analysis, the depth of 1.5m~3.0m was appropriate for minimizing the submersion of basements and for making the disposal of domestic wastewater more easily.

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.

Anaerobic Digestion of thickened septage was investigated in this study. Thickening could reduce the volume of septage to be treated to about 40% with 12hr HRT. The VS and BOD removal efficiencies were respectively 28 to 45%, and 75% when digested the thickened septage with 30 day HRT Or $1.4kgVS/m^3/d$. The BOD removal efficiency could be increased to about 90% with subsequent settling tank with about 6 hours HRT. The gas production rate was 0.22 to $0.35m^3gas/kgVSadd$($0.75m^3gas/kgVSrm$), or $1.32m^3gas/kgBOD_{rm}$. In addition, the supernatant of thickener could be returned to the aeration tank treating domestic sewage. In this case, a BOD loading rate of 0.5 to $0.7kgBOD/m^3/d$ or 0.5kgBOD/kgMLVSS/d was proposed for 80% BOD reduction.

미국 캘리포니아주 Orange County에 위치한 Water Factory 21(WF-21)은 생물학적 처리공정을 거친 도시하수를 재생하여, 이 재생수를 지하수지층으로 유입되는 해수의 침투를 막기 위한 Reinjection System에 이용하고 있다. 장치 구성 공정은 Lime처리, Air Stripping, 사여과, 활성탄처리, 역삼투막 및 염소처리 등으로 이루어지며, 이에 대한 각 처리공정의 효율성에 대하여 실험을 실시하였다. 3년간의 장기간에 걸친 실험결과로부터, 도시하수에 대한 RO Membrane 처리수는 음료 수질 기준에 적합한 고수질의 물을 생성할 수 있음을 입증했다. Pilot Plant 실험에선 Lime Clarifier만으로 전처리를 실시하여 성공적인 결과를 얻었으며, 또한 저압 (250 psi)이 적용된 새로운 Membrane을 사용하여 에너지 절약을 통한 비용 절감 효과에 대한 실험도 상당한 가능성을 보여주었다.

This study investigated microbial communities and their diversity in a full-scale mesophilic anaerobic digester treating sewage sludge. Influent sewage sludge and anaerobic digester samples collected from a wastewater treatment plant in Busan were analyzed using high-throughput sequencing. It was found that the microbial community structure and diversity in the anaerobic digester could be affected by inoculation effect with influent sewage sludge. Nevertheless, distinct microbial communities were identified as the dominant microbial communities in the anaerobic digester. Twelve genera were identified as abundant bacterial communities, which included several groups of syntrophic bacteria communities, such as Candidatus Cloacimonas, Cloacimonadaceae W5, Smithella, which are (potential) syntrophic-propionate-oxidizing bacteria and Mesotoga and Thermovigra, which are (potential) syntrophic-acetate-oxidizing bacteria. Lentimicrobium, the most abundant genus in the anaerobic digester, may contribute to the decomposition of carbohydrates and the production of volatile fatty acids during the anaerobic digestion of sewage sludge. Of the methanogens identified, Methanollinea, Candidatus Methanofastidiosum, Methanospirillum, and Methanoculleus were the dominant hydrogenotrophic methanogens, and Methanosaeta was the dominant aceticlastic methanogens. The findings may be used as a reference for developing microbial indicators to evaluate the process stability and process efficiency of the anaerobic digestion of sewage sludge.

With the introduction of the tele-monitoring system (TMS) in South Korea, monitoring of the concentration of pollutants discharged from nationwide water quality TMS attachments is possible. In addition, the Ministry of Environment is implementing a smart sewage system program that combines ICT technology with wastewater treatment plants. Thus, many institutions are adopting the automatic operation technique which uses process operation factors and TMS data of sewage treatment plants. As a part of the preliminary study, a multilayer perceptron (MLP) analysis method was applied to TMS data to identify predictability degree. TMS data were designated as independent variables, and each pollutant was considered as an independent variables. To verify the validity of the prediction, root mean square error analysis was conducted. TMS data from two public sewage treatment plants in Chungnam were used. The values of RMSE in SS, T-N, and COD predictions (excluding T-P) in treatment plant A showed an error range of 10%, and in the case of treatment plant B, all items showed an error exceeding 20%. If the total amount of data used MLP analysis increases, the predictability of MLP analysis is expected to increase further.

The purpose of this study was to evaluate the operational characteristics of wastewater treatment using Sequencing Batch Reactor (SBR) with Aerobic Granular Sludge (AGS) separator in the pilot plant. Pilot plant experiments were conducted using SBR with AGS separator and pollution removal efficiencies were evaluated based on the operational condition and surface properties of AGS. The results of the operation on water quality of the effluent showed that the average concentration of total organic carbon, suspended solids, nitrogen, and phosphorus was 6.89 mg/L, 7.33 mg/L, 7.33 mg/L, and 0.2 mg/L, respectively. All these concentrations complied the effluent standard in Korea. The concentration of mixed liquor suspended solid (MLSS) fluctuated, but the AGS/MLSS ratio was constant at 86.5±1.3%. Although the AGS/MLSS ratio was constant, sludge volume index improved. These results suggested that the particle discharged fine sludge and increased the AGS praticle size in the AGS. Optical microscopy revealed the presence of dense AGS at the end of the operation, and particles of > 0.6 mm were found. Compared to those of belt-type AGS separator, the required area and power consumption of the hydrocyclone-type AGS separator were reduced by 27.5% and 83.8%, respectively.

The role of the distribution basin role is to apportion incoming raw water to the primary sedimentation basin as part of the water treatment process. The purpose of this study was to calculate the amount of water in the distribution basin using computational fluid dynamics (CFD) analysis and to find a way to improve any non-uniformity. We used the Taguchi method and the minitab tool as optimization methods. The results of the CFD calculation showed that the distribution flow had a deviation of 5% at the minimum inflow, 10% at the average inflow, and 22% at the maximum inflow. At maximum flow, the appropriate heights of the 7 weirs(C, D, A, B, E, F, G) were 40 mm, 20 mm, 20 mm, 0, 0, 0, and 20 mm, respectively, according to the Taguchi optimization tool. Here, the maximum deviation of the distribution amount was 9% and the standard deviation was 23.7. The appropriate heights of the 7 weirs, according to the Minitab tool, were 40 mm, 20 mm, 20 mm, 0, 0, 0, and 20 mm, respectively, for weirs C, D, A, B, E, F, and G. Therefore, the maximum deviation of the distribution amount was 8% and the standard deviation was 17.1, which was slightly improved compared to the Taguchi method.

In this study, we evaluated the effect of the type of sewage sludge (digested, non digested) on drying efficiency according to the polymer injection rate. The drying characteristics were shown using a near-infrared ray (NIR) and a microwave. As a result of the drying characteristics with NIR at a polymer dose ratio of 8%, the heating up period is up to 6 minutes after the start of the drying experiment. Afterwards, the constant rate drying period of the digested sludge (A, C and G sites) was 6 minute → 18 minute, showing a rapid decrease in moisture. On the other hand, non digested sludge (B, D, E, F, H, I, J and K sites) showed gradual drying characteristics compared to digested sludge until complete drying (10%). As the polymer dose ratio of 10% and 12%, the heating up period for digested sludge is up to 6 minute after the start of the experiment. Afterwards, the constant rate drying period of the digested sludge was 6 minute → 20 minute, showing a rapid decrease in moisture. On the other hand, the heating up period of non digested sludge was up to 10 minute after the start of the experiment, and the constant rate drying period was 10 minute → 22 minute, which was shorter than digested sludge. As a result of the drying characteristics with microwave at a polymer dose ratio of 8%, 10% and 12%, the constant rate drying period the digested sludge was 4 minute → 20~22 minute, showing a rapid decrease in moisture. On the other hand, non digested sludge of the constant rate drying period was 4 minute → 22~30 minute, which was longer than digested sludge.

This study was initiated to isolate the microorganisms removing phosphorus (P) from domestic sewage and to investigate the effects of environmental factors on the growth and P removal of the isolated bacteria. Microorganisms isolated from the sewage were identified as Chryseobacterium sp., Stenotrophomonas maltophilia, and Bacillus licheniformis. Among them, Bacillus licheniformis was selected as the P removal microorganism. The environmental factors considered in this study included initial phosphorus concentration, temperature, pH, and carbon source. At initial P concentrations of 10, 20, and 30 mg/L, the P removal efficiencies were 100.0%, 84.0%, and 16.5%, respectively. At 20°C, 30°C, and 40°C, the P removal efficiencies were 0%, 75.8%, and 60.6%, respectively. The removal efficiencies of phosphorus according to pH were 1.6%, 91.7%, and 51.1% at pH 5, pH 7, and pH 9, respectively. Using glucose, acetate, and glucose + acetate as carbon sources yielded P removal efficiencies of 80.9%, 33.6%, and 54.1%, respectively. Therefore, the results from the study demonstrated that the P removal efficiencies of Bacillus licheniformis were the highest when the initial P concentration, temperature, pH, and carbon source were 10 mg/L, 30°C, 7, and glucose, respectively.