• 상하수도학회지
• /
• 제26권6호
• /
• pp.889-896
• /
• 2012

In this study, simulation results of nitrogen and phosphorus removals and microbial activities for an $A_2O$ process in wastewater treatment plant are presented by using Activated Sludge Models (ASMs). Simulations were performed using pre-calibrated model and layout implemented in GPS-X simulation software. The models were used to investigate variations of SRT, water temperature, DO and C/N ratio effect on nutrients removal and microbial activity. According to the simulated results, the successful nitrification required SRT higher than 10.3 days, whereas increase of $NO_3$-N loading in the anaerobic reactor caused phosphorus release by PAOs; the effluent $NH_4$-N showed rapid change between $12^{\circ}C$(21.7 mg/L) and $13^{\circ}C$(3.2 mg/L); the effluent phosphorus was increased up to 1.9 mg/L at water temperature of $25^{\circ}C$; the DO increase was positive for heterotrophs and autotrophs growths but negative for PAOs growth; the PAOs showed low activity when C/N ratio was lower than 2.5. The experimental results indicated that the calibrated models can assure the prediction quality of the ASMs and can be used to optimize the $A_2O$ process.

• 한국수산과학회지
• /
• 제35권2호
• /
• pp.146-154
• /
• 2002

황토살포에 따른 해수중 영양염 제거효율 및 제거기구를 파악하기 위하여 황토의 입자 크기와 살포농도에 따른 경과시간별 해수중 영양염 농도변화를 실내 실험을 통하여 측정하였다 53$\mu$m 이하에서 500$\mu$m 크기범위의 황토입자를 해수중에 첨가하여 24시간이 경과 후, 인산인의 제거효율은 황토 살포농도에 따라 59$\~$$99\%$까지 변하였으며, 살포농도가 증가할수록 제거효율은 높게 나타났다. 그러나, 황토 입자크기에 따른 인산인의 제거효율의 차는 그다지 크지 않았다 규산규소의 제거효율은 황토입자 크기 및 살포 양의 차이에 관계없이 평균 약 $26\%$가 일정하게 감소하였다. 해수중 황토 살포 후, 인산인의 제거기구를 파악하기 위한 인의 존재형태별 분석결과는 $99\%$ 이상의 인산인이 철성분에 의한 화학적인 결합에 의해 제거된다는 것을 나타내었고, 규산규소는 해수와 황토 내에 들어있는 양이온과의 이온교환에 의하여 제거되는 것을 시사해 주었다

• 대한환경공학회지
• /
• 제35권4호
• /
• pp.283-288
• /
• 2013

침수식물인 Ceratophyllum demersum (C. demersum)의 영양염류 제거 효율과 남조류 성장 억제 능력을 평가하기 위해 총 6개의 반응조에서 9일간 회분식 실험을 실시하였다. 실험이 시작되고 약 84 hr 후 C. demersum는 pH, DO에 대한 안정적인 일주기 경향을 보였다. 영양염류인 $NH_3{^+}$, $NO_3{^-}$, $PO{_4}^{3-}$를 대상으로 저감률을 검토한 결과 실험초기부터 9일간 지속적인 감소를 보였고 특히 24 hr 이내에서 빠른 감소를 나타내었다. C. demersum의 단위면적당 생체량과 영양염류 제거율 사이에 높은 상관관계($r^2{\geq}0.96$, p<0.001)가 도출되었으며, 피복도가 높을수록 오염물 저감 효율이 큰 것으로 나타났다. 하지만 높은 밀도의 반응조에서는 C. demersum의 활성화 차이가 있었으며, 그럼에도 불구하고 수질정화 효과가 나타난 것은 침수식물에 존재하는 부착조류나 미생물의 영향이 큰 것으로 여겨진다. Microcystis aeruginosa (M. aeruginosa)는 C. demersum의 생장밀도 2,500 g $fw/m^2$ (피복도 100%) 조건에서 성장률 0.31 /day를 보였으나 대조구는 0.47 /day을 나타내었다. 세포수 비교에서는 실험구보다 대조구가 약 1.7배 높게 나타나 C. demersum의 남조류 성장 억제 능력을 시사하였다.

• Ocean and Polar Research
• /
• 제26권1호
• /
• pp.102-111
• /
• 2004

Recirculating aquaculture system (RAS) consists of different treatment compartments that maintain water quality within the ranges commonly recommended for fish cultures. However, common RASs still exert considerable environmental impact since concentrations of organic matter and nutrients in their effluents are high. Compared with the traditional RAS, the model RAS developed here use a sedimentation basin for digestion purposes and then use the released volatile organic matter to stimulate a denitrification process. Different treatment compartments for solids, total ammonia nitrogen, and nitrate removal have been reviewed. This paper provides the basic information on designing different treatment compartments as well as the engineering criteria in closed seawater RAS, consisting of circular tanks for fish cultures; dual drain systems, sedimentation basins and foam fractionators for removal of solids; nitrification biofilters for TAN removal; denitrification biofilters for nitrate removal; and aerators for aeration. The main purpose is to outline a common procedure in designing of closed RAS for marine fish culture with an emphasis on easy management and low expense, as well as reduction of the environmental impact.

• 상하수도학회지
• /
• 제22권3호
• /
• pp.359-366
• /
• 2008

The series of experiments under the various conditions were carried out to evaluate the feasibility of dissolved air flotation (DAF) as an alternative of conventional gravity sedimentation (CGS) and to investigate the decrease of the loadings following to biological wastewater treatment processes in livestock wastewater system. On the basis of the experiment result between CGS and DAF processes, for the other water quality criteria as well as suspended solid the removal efficiency of DAF process was about 20~25 % better than CGS process on average. In addition, the particle removal efficiency of DAF process became higher in proportion as the increase of air to solid (A/S) ratio and the general wastewater treatment efficiency of DAF process was enough to meet the requirement of loading decrease to following biological process even at low A/S ratio range. Though DAF process is widely known as an solid separation unit, there was not the notable relationship between particle separation efficiency and several pollutant removal efficiencies like $COD_{Cr}$ and nutrients (T-N, T-P). Assume that the $COD_{Cr}$ was removed as the fraction of particle separation in this experiment, the removal efficiency of T-N and T-P were sensitive to removal efficiency of $COD_{Cr}$, especially.

• 상하수도학회지
• /
• 제22권4호
• /
• pp.449-454
• /
• 2008

Some pretreatment methods have been proposed to enhance the biodegradability and to shorten the hydrolysis reaction time. By means of efficient pretreatment the suspended solids (SS) can be made of better accessible for the anaerobic bacteria. There are several ways how this can be accomplished, which include biological, mechanical, thermal, and chemical methods. For the sludge solubilization using the cavitation phenomenon, we have tried to develop a pretreatment process consisted of a reactor and pumps. The objectives of this study were to develop a advanced wastewater treatment consisted of IABR and the cavitation with PGA. The most effective removal for organic matter and nutrients were occured when both cavitation pretreatment and ${\gamma}$-PGA were applied at the IABR process. Only small portion of ${\gamma}$-PGA at a rate of 1.38mg/L, was enough to improve sedimentation ability, SS removal efficiencies, and sludge volume reduction. After the sludge solubilization by the cavitation, SCOD increased to 193% and SS decreased to 36%. The removal ratio of BOD was 94.5%, T-N removal ratio was 85.5% and T-P removal ratio was 84.9%. The combination process of the IABR with the cavitation and PGA addition seems to be very effective alternative wastewater treatment process.

• 한국환경보건학회지
• /
• 제23권4호
• /
• pp.133-138
• /
• 1997

The technology of removing phosphorous, considered as one of the most important control nutrients causing eutrophication in various water bodies, have been investigated by many researchers. Recently, phosphorous crystallization process is emerging as a new technology for phosphorous removal. In this study, waste oyster shells which can be easily obtained from the ocean, were used as a seed crystal, and their effects of several physical/chemical factors on the phosphorous removal efficiencies were examined by batch tests. Ca$^{2+}$ and pH affected phosphorous crystallization process using waste oyster shells. As alkalinity of wastewater increased, phosphorous removal efficiencies gradually decreased. Phosphorous removal efficiencies were increased, as specific area and contact efficiency per unit area of waste oyster shells were increased. In case of high temperature, phosphorous crystallization process was rapidly advanced and phosphorous removal efficiencies were increased. Dependig on X-ray diffraction analysis, it was showed that generation materials extracted from the surface of waste oyster shells with short reaction time were dominated by $CaHPO_4\cdot 2H_2O$, but progressed to $Ca_5(OH)(PO_4)_3$. The SEM observation reveals that the evident variations were hardly seen, but particle sizes of waste oyster shells were relatively bigger and showed forms of smaller plate than before.

• Environmental Engineering Research
• /
• 제23권4호
• /
• pp.364-373
• /
• 2018

The present study assessed the efficient removal of nutrients and Chlorophyll-a (Chl-a) by using methyl esterified sericite (MES) and pine needle extracts (PNE), a low cost and abundant green hybrid material from nature. For this purpose, the optimal conditions were investigated, such as the pH, temperature, MES and PNE ratio, and MES-PNE dose. In addition, a Microcystis aeruginosa control using MES-PNE was also analyzed with various inhibition models. The removal of the nutrient and Chl-a onto MES-PNE was optimized for over 95% removal as follows: 2-2.5 for the MES-PNE ratio, 7-8 pH and a $22-25^{\circ}C$ temperature. In this respect, approximately 1.52-2.20 g/L of MES-PNE was required to remove each 1 g of dry weight/L of Chl-a. Total phosphorus (TP) has a greater influence on the increase in Chl-a than total nitrogen (TN) according to the correlation between TN, TP and Chl-a. Moreover, the Luong model was the best model for fitting the biodegradation kinetics data from Chl-a on MES-PNE from lake water. The novel hybrid material MES-PNE was very effective at removing TN, TP and Chl-a from the lake and can be applied in the field.

• 한국환경보건학회지
• /
• 제37권1호
• /
• pp.64-72
• /
• 2011

This study was performed to assess the removal efficiency on nitrogen, phosphorus and organic carbon in wastewater by spatial separation and internal recycling in a modified oxidation ditch process (modified OD). The performances of the modified OD were evaluated via laboratory-scale experiments. The process was operated at hydraulic retention times of 6-48 hours and solid retention times of 17-38 days. We found that organic carbon removal efficiency increased after the modified OD operation period. T-N removal efficiency remained stable; average T-N concentration of effluent was 8.02 mg/l after modified OD operation. In contrast, T-P concentration of effluent was over 1 mg/l. Nitrogen and phosphorus removal efficiency of modified OD at HRT 12 hr were 83.1% and 74.1%, respectively. Also, maximum efficiency was found at SRTs from 20 to 30 days. T-N removal efficiency was 83.1% at a C/N ratio from 3.0 to 3.5. However, T-N removal efficiency decreased at C/N ratios over 3.5. Also, T-P removal efficiency increased with HRT at C/P ratios in the same condition. Maximum efficiency was 74.1% at a C/P ratio from 25 to 28. T-N removal efficiency was 79.2% and T-P removal efficiency was 65.3% after M4 mode operation (added to the internal recycle line connected to the anoxic reactor). The modified OD with spatial separation and internal recycling developed in this study is, therefore, believed to be an improvement for solving problems in the nutrient removal technologies.

• 대한환경공학회지
• /
• 제33권5호
• /
• pp.314-324
• /
• 2011

하수를 이용해서 배양된 조류는 바이오디젤 생산에 유용한 자원이다. 그러나 실제 하수에서 조류의 영양염류 신진대사와 하수 세균과의 상호작용에 관한 연구는 미흡하다. 본 연구에서는 하수로 배양되는 대표적 조류균주인 Ankistrodesmus gracilis SAG 278-2에 의한 하수 내 질소, 인 제거 거동을 평가하였고, 조류와 상호작용하는 하수 내의 세균 군집을 분석하였다. 하수 슬러지 세균 군집과 비교하였을 때, 조류-세균 복합 군집은 하수 내보다 높은 영양염류 제거를 보였다. 16S rRNA 유전자 분석 결과, 조류-세균 군집에서 조류가 성장함에 따라 Unclassified Alcaligenaceae 세균이 선택적으로 우점됨을 알 수 있었고, 조류에 의해서 선택적으로 우점화된 하수세균은 자연 수질 환경에서 조류와 공생적으로 상호작용 하는 것으로 알려진 Alcaligenes faecalis subsp. 5659-H와 계통학적으로 가까운 것으로 밝혀졌다. 본 연구의 결과, 하수 내의 높은 영양염류 제거를 보이는 조류-세균 복합 군집에서의 조류의 성장 및 신진대사가 특정 세균의 분포에 영향을 주는 것을 알 수 있었다.