Small hydropower systems have emerged as an attractive solution for areas with low head and flow rates, offering versatility for implementation in diverse locations such as rivers and wastewater treatment plants. This research specifically focuses on exploring the potential of small hydropower generation within wastewater treatment plants. Through the utilization of computational fluid dynamics (CFD) analysis, the study successfully predicted the torque and power generation capacity of the installed turbine. The analysis underscored the effective control of fluid flow achieved through careful turbine design, including considerations of blade shape and quantity. For instance, in the case of the Tancheon wastewater treatment plant, the study revealed the ability to generate a torque of approximately 7000 Nm, translating to an estimated power production of around 48.3 kW per hour. Ultimately, this research significantly contributes to evaluating the feasibility and viability of small hydropower generation within wastewater treatment plants.
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.
본 연구에서는 하수 재이용을 위한 역삼투막 공정에서 전처리 정밀여과막(MF) 손상에 대한 누출되는 다양한 수 질변화로써 막 손상 검지 방안을 제시하였다. 이를 위하여 역삼투막 유입수질 적합성 평가지표인 SDI (silt density index)를 3에서 5의 범위 내에서 막 손상 시 검지 감도를 정량화하기 위하여 전처리 분리막이 1에서 3가닥 파단에 따라 SDI는 1.92에 서 6.11까지 증가한 결과를 확인할 수 있었다. 일반적으로 3을 기준으로 역삼투막 유입수질로 설정하였을 때 분리막이 3가닥 까지 파단이 되어야만 막 손상 검지가 가능하다는 것을 의미하며 역삼투막의 오염은 잠재적으로 가속화되어 효율을 저하시 킬 수 있다. 또한 이때 누출되는 입자성과 유기물질에 대하여 0.45 μm 이상의 크기만 걸러주는 입자계수는 입도분포별 막 파 단 개수에 따라 일정한 패턴을 확인할 수 없었으며, TOC 농도는 약 2배의 변화패턴으로써 SDI와의 상관관계로써 TOC가 막 손상 수질지표로써 신뢰성이 높은 것으로 확인되었다. 수질분석결과와 더불어 USEPA에서 제시하는 막 손상 검지 방법 중 압력손실시험과 이를 기반으로 LRVDIT 모델의 적합성 평가를 한 결과 막 손상 또는 역삼투막 공정으로 유입되는 막오염물질 을 신속하게 확인할 수 있는 SDI 및 TOC를 포함한 LRVDIT 모니터링과 UCL 설정을 병행해야 한다.
The sewer capacity design have been based on the Huff model or the rational equation in South Korea and often failed to determine optimal capacity, resulting in frequent urban flooding or over-sizing. A time distribution of rainfall (i.e., Huff or ABM method) could be used instead of a rainfall hyetograph obtained from statistical analysis of previous rainfalls. In this study, the Huff method and the ABM method, which predict the time distribution of rain intensity, which are widely used to calculate sewage pipe drainage capacity using the SWMM, were compared with the standard rainfall intensity hyetograph of Seoul. If the rainfall duration was 30 minutes to 180 minutes, the rainfall intensity value calculated by the Huff model tended to be less than the rainfall intensity value of the standard rainfall intensity in the initial 5-10 minutes. As a result, more than 10% to 30% of under-design would be made. In addition, the rainfall intensity value calculated by the Huff model from the section excluding the initial 5-10 minutes of rainfall to the rainfall duration was calculated larger than the value using the standard rainfall intensity equation, which would result in an over-design of 10% to 30%. In the case of a relatively long rainfall duration of 360 minutes (6 hours) to 1,440 minutes (24 hours), it showed an lower rainfall intensity of 60 to 90% in the early stages of rainfall, but the problem of under-design had been solved as the rainfall duration time had elapsed. On the other hand, in the alternating block method (ABM) method, it was found that the rainfall intensity at the entire period at each assumed rainfall duration accurately matched the standard rainfall intensity hyetograph of Seoul.
자기공명영상(MRI) 장비의 조영제로 흔히 사용되는 가돌리늄(Gd)은 매우 안정된 상태로 하수처리과정에서 거의 제거되지 않고 수환경으로 유입된다고 알려져 있다. 따라서 본 연구에서는 세 가지의 공법으로 하수처리를 하는 부산 수영 하수처리장에서 채취한 하수 시료의 공정별 용존 희토류 원소의 제거율 및 수환경으로 배출되는 인위적 기원 Gd (Gdanth)의 배출량을 평가하고자 하였다. 용존 희토류 원소는 공정별 처리 단계에 따라 무거운 희토류 원소(Tb-Lu)에 비 해 가벼운 희토류 원소(La-Eu)에서 농도가 감소하는 경향을 보였다. 또한 일부 시료에서 나타난 음의(negative) Sm anomaly (<1)는 생물학적 제거 과정에서 Sm이 입자나 인산염과 흡착되어 함께 제거되었을 가능성을 시사한다. 모든 시 료에서 양의(positive) Gd anomaly (149±50, n=9)를 보였으며, 공정별로 측정된 Gd의 총 농도 중 Gdanth은 약 97% 이 상을 차지하는 것으로 나타났다. 이는 하수처리과정에서 Gdanth 이 거의 제거되지 않고 수영강 하류로 배출된다는 것을 의미한다. 일별 처리용량을 고려하여 각 공정에서 배출되는 Gdanth의 배출량은 259 mmol/day로 추정할 수 있다. 본 연 구의 결과는 하수처리장을 통해 수영만 연안으로 Gdanth이 지속적으로 배출될 것으로 예상되며, 향후 Gd의 중장기적인 관측이 필요함을 시사한다.
The frequent detection and occurrence of micropollutants (MPs) in aquatic ecosystems has raised public health concerns worldwide. In this study, the behavior of 50 MPs was investigated in three different domestic wastewater treatment plants (WWTPs). Furthermore, the Kruskal-Wallis test was used to assess the geographical and seasonal variation of MPs in the WWTPs. The results showed that the concentrations of 43 MPs ranged from less than 0.1 to 237.6 μg L-1, while other seven MPs including 17-ethynylestradiol, 17-estradiol, sulfathiazole, sulfamethazine, clofibric acid, simvastatin, and lovastatin were not detected in all WWTPs. Among the detected MPs, the pharmaceuticals such as metformin, acetaminophen, naproxen, and caffeine were prominent with maximum concentrations of 133.4, 237.6, 71.5, and 107.7 μg L-1, respectively. Most perfluorinated compounds and nitrosamines were found at trace levels of 1.2 to 55.3 ng L-1, while the concentration of corrosion inhibitors, preservatives (parabens), and endocrine disruptors ranged from less than 0.1 to 4310.8 ng L-1. Regardless of the type of biological treatment process such as MLE, A2O, and MBR, the majority of pharmaceuticals (except lincomycin, diclofenac, iopromide, and carbamazepine), parabens (except Methyl paraben), and endocrine disruptors were removed by more than 80%. However, the removal efficiencies of certain MPs such as atrazine, DEET, perfluorinated compounds (except PFHxA), nitrosamines, and corrosion inhibitors were relatively low or their concentration even increased after treatment. The results of statistical analysis reveal that there is no significant geographical difference in the removal efficacy of MPs, but there are temporal seasonal variations in all WWTPs.
Conventional wastewater treatment plants (WWTPs) do not fully remove micropollutants. Enhanced treatment of sewage effluents is being considered or implemented in some countries to minimize the discharge of problematic micropollutants from WWTPs. Representative enhanced sewage treatment technologies for micropollutant removal were reviewed, including their current status of research and development. Advanced oxidation processes (AOPs) such as ozonation and UV/H2O2 and adsorption processes using powdered (PAC) and granular activated carbon (GAC) were mainly discussed with focusing on process principles for the micropollutant removal, effect of process operation and water matrix factors, and technical and economic feasibility. Pilot- and full-scale studies have shown that ozonation, PAC, and GAC can achieve significant elimination of various micropollutants at economically feasible costs(0.16-0.29 €/m3). Considering the current status of domestic WWTPs, ozonation and PAC were found to be the most feasible options for the enhanced sewage effluent treatment. Although ozonation and PAC are all mature technologies, a range of technical aspects should be considered for their successful application, such as energy consumption, CO2 emission, byproduct or waste generation, and ease of system construction/operation/maintenance. More feasibility studies considering domestic wastewater characteristics and WWTP conditions are required to apply ozonation or PAC/GAC adsorption process to enhance sewage effluent treatment in Korea.
철근 콘크리트 하수관거는 경제적 장점과 내구성으로 인해 많이 사용되고 있다. 오랜 공용시간 이후 하수관거는 하 수의 산화물과 공용하중에 의해 열화가 진행된다. 본 논문은 초고강도 콘크리트로 갱생한 열화된 콘크리트 하수관거의 구조적 성능에 대해 연구하였다. 실험변수는 초고강도 콘크리트 관거 상부슬래브와 벽체의 두께의 조합으로 구성하였다. 네가지 종류의 초고강도 콘크리트 관거가 극한하중을 받을 때까지 내하력을 파악하기 위해 실험을 진행하였다. 보통 강도 콘크리트에 비해 상 대적으로 작은 두께의 초고강도 콘크리트 관거는 열화된 내부 부분을 치핑하고 갱생함으로써 단면의 손실을 최소화할 수 있다. 실험결과에 의하면 열화된 콘크리트 관거를 갱생하는데 적용된 새로운 얇은 두께의 초고강도 콘크리트 구조물이 재하하중을 만 족하고 실제 공학적 적용에 용이성을 있음을 나타내고 있다.
N-nitrosodimethylamine (NDMA) is a potent carcinogen that is frequently detected nitrosamine from water chloramination. This study investigated the occurrence of NDMA and its potential precursor, ranitidine (RNT), in four wastewater treatment plants (WWTPs). Additionally, the effects of chloramination methods and oxidative pretreatment on the NDMA formation potential (FP) were assessed. Concentration levels of NDMA in the WWTPs waters ranged from 2.5 (detection limit) to 72.6 ng/L, while RNT values ranged from 1.32 to 186.9 ng/L. Further study indicated that the NDMA-FPs from chloraminated wastewaters varied between 36.2 and 227.8 ng/L. Nonetheless, chloramination methods and oxidative pretreatment significantly impacted the NDMA-FP levels. For example, breakpoint chlorination and stepwise chloramination promoted NDMA-FP when compared to preformed chloramination, which could be attributed to the formation of dichloramine and chlorine species. In contrast, prechlorination was found to effectively mitigate NDMA-FP, based on integrated ultraviolet (UV) irradiation. Notably, UV irradiation with free chlorine (UV/Cl2) or permanganate (UV/MnO4 -) reduced NDMA-FP by up to 70%. This study suggests that UV/MnO4 - and UV/Cl2 may be used as alternative mitigation strategies for reducing nitrosamine-FP in the water treatment process.
Due to the global climate change, Korean peninsula is has been experiencing flooding and drought severely. It is hard difficult to manage water resources sustainably, because due to intensive precipitation in short periods and severe drought has increased in Korea. Reused water from the wastewater treatment plant (WWTP) could be a sustainable and an alternative water source near the urban areas. In order to understand the patterns of water reuse in Korea, annual water reuses data according to the times and regional governments were investigated from 2008 to 2019. The reused water from WWTP in Korea has been mainly used for river maintenance flow and industrial use, while agricultural use of water reuse has decreased with time. Metropolitan cities in Korea such as Seoul, Busan, Daegu, Ulsan, and Incheon have been mainly used reused reusing water for river maintenance flow. Industrial water reuse has been limitedly applied recently for the planned industrial districts in Pohang, Gumi, Paju, and Asan. By using the collected annual water reuse data from the domestic sewerage statistics of sewerage, the optimistic and pessimistic future estimations of for future annual water reuse were suggested from 2020 to 2040 on a five year interval for every five years.
Due to the large-scale production and use of synthetic chemicals in industralized countries, various chemicals are found in the aquatic environment, which are often termed as micropollutants. Effluents of municipal wastewater treatment plants (WWTPs) have been identified as one of the major sources of these micropollutants. In this article, the current status of occurrence and removal of micropollutants in WWTPs and their management policies and options in domestic and foregin countries were critically reviewed. A large number of pharmaceuticals, personal care products, and industrial chemicals are found in WWTPs’ influent, and are only partially removed by current biological wastewater treatment processes. As a result, some micropollutants are present in WWTPs’ effluents, which can negatively affect receiving water quality or drinking water source. To better understand and assess the potential risk of micropollutants, a systematic monitoring framework including advanced analytical tools such as high resolution mass spectrometry and bioanalytical methods is needed. Some Western European countries are taking proactive approach to controlling the micropollutants by upgrading WWTP with enahnced effluent treatment processes. While this enahnced WWTP effluent treatment appears to be a viable option for controlling micropollutant, its implementation requires careful consideration of the technical, economical, political, and cultural issues of all stakeholders.
The quantified analysis of damages to wastewater treatment plants by natural disasters is essential to maintain the stability of wastewater treatment systems. However, studies on the quantified analysis of natural disaster effects on wastewater treatment systems are very rare. In this study, a total disaster index (DI) was developed to quantify the various damages to wastewater treatment systems from natural disasters using two statistical methods (i.e., AHP: analytic hierarchy process and PCA: principal component analysis). Typhoons, heavy rain, and earthquakes are considered as three major natural disasters for the development of the DI. A total of 15 input variables from public open-source data (e.g., statistical yearbook of wastewater treatment system, meteorological data and financial status in local governments) were used for the development of a DI for 199 wastewater treatment plants in Korea. The total DI was calculated from the weighted sum of the disaster indices of the three natural disasters (i.e., TI for typhoon, RI for heavy rain, and EI for earthquake). The three disaster indices of each natural disaster were determined from four components, such as possibility of occurrence and expected damages. The relative weights of the four components to calculate the disaster indices (TI, RI and EI) for each of the three natural disasters were also determined from AHP. PCA was used to determine the relative weights of the input variables to calculate the four components. The relative weights of TI, RI and EI to calculate total DI were determined as 0.547, 0.306, and 0.147 respectively.