BOD Loading Research Articles

오염총량관리제의 시공간적 미래 토지이용 변화분석을 위한 CLUE-S 모델의 적용 및 평가

The purpose of this study is to predict the spatio-temporal changes in land uses and to evaluate land-based pollutant loads in the future under Total Water Pollution Load Management System using CLUE-S model. For these ends, sensitive parameters of conversion elasticities in CLUE-S model were calibrated and these calibrated parameters of conversion elasticities, level II land cover map of year 2009, and 7 driving factors of land use changes were used in predicting future land uses in 2002 with two scenarios(Scenario 1: non area restriction, Scenario 2: area restriction). This projected land use map of 2020 was used to estimate land-based pollutant loads. It was expected that urban areas will increase in 2020 from both scenarios 1 and 2. In Scenario 1, urban areas are expected to increase within greenbelt areas and deforest would be expected. Under Scenario 2, these phenomena were not expected. Also the results of estimation of BOD and TP pollutant loads, the BOD difference between scenarios 1 and 2 was 719 kg/day in urban areas and TP difference was 17.60 kg/day in urban areas. As shown in this study, it was found that the CLUE-S model can be useful in future pollutant load estimations because of its capability of projecting future land uses considering various socio-economic driving factors and area-restriction factors, compared with conventionally used land use prediction model.

Non-point sources of pollution from cultivated lands in river districts and their contribution to water bodies along the North Han River Basin in Korea

Cultivated lands within the river district are likely non-point sources of pollution that could be directly discharged into rivers and lakes, as well as identified as significantly risky areas for pollutant run-off during floods. In this study, major non-point sources in surface run-offs, from cultivated lands within the river districts, and their effects on the bodies of water in North Han River Basin were examined. It was found that pollutant concentrations in the run-offs from farms appeared to be generally higher than in the run-offs from paddies. Initial concentrations of pollutants during rainy seasons were usually higher than the medians of their concentration ranges, though not necessarily the highest. The unit loads of BOD from cultivated lands within river districts, which were proposed in this study for the first time in Korea, were 4.56, 3.35, and 10.26 kg/km2/year for paddies, farms, and greenhouses, respectively. Likewise the unit loads of total nitrogen (TN) were proposed as 1.54, 8.11, and 5.59 kg/km2/year for paddies, farms, and greenhouse, respectively. Meanwhile, the unit loads of Total phosphorus (TP) were 0.71, 2.79, and 1.11 kg/km2/year for paddies, farms, and greenhouses, respectively. The unit loads for both BOD and TP from paddies and farms in the North Han River basin were higher than those provided by the Ministry of Environment. It was largely attributable to the regional characteristics of the cultivated area, within the river district, that is adjacent to the water system. Three priority standard watersheds, which were believed to contain higher non-point sources of pollution than other standard watersheds, were recommended to undergo restoration. The sum of the discharged total loads per unit area for BOD, TN, and TP from these three standard watersheds (i.e. NHR M2, NHR1, and NHR M) was 71.8, 71.5, and 73.0%, respectively. Restoring cultivated lands within river districts into grasslands could effectively reduce the total load of TP rather than BOD and TN. Therefore, converting cultivated lands within river districts back to grasslands can be an alternative in effectively reducing pollution in bodies of water.

팔당호 상류의 단위유역별 오염물질 유출특성 분석을 통한 중점관리 오염원 선정

Paldang lake which is the most important water resource in Korea is classified as a stream type reservoir and water quality of Paldang lake can be significantly influenced by external pollutant source. So this study was aimed to determine focused control BOD and TP sources of each unit watershed upper Paldang lake through analysis of pollutant source distribution and pollutant runoff characteristics. Generated load, discharge load, delivery load and each load density of 11 unit watersheds upper Paldang lake were calculated using data of water quality and flow rate from pollutant sources and 74 small streams. As a result of generated load, discharge load and delivery load of BOD and TP from pollutant sources, the most BOD generated load was taken by livestock with 66% of total BOD discharge load and domestic had the most BOD discharge load, 42.7%. The ratio of delivery load of livestock and domestic was 36.4% and 34.3%, respectively. Livestock occupied high ratio of TP generated load, discharge load and delivery load with 82.5%, 44.4% and 46.7%, respectively. Gyeongan watershed which had high population density showed the highest BOD delivery load density of 14.6 kg/km/d and the highest TP delivery load density with 1.23 kg/km/d was analyzed in Cheongmi watershed including the biggest number of livestock. From these results, management of domestic sewer and livestock excrement was determined as a focused control pollutant source. And intensive management about domestic sewer in Gyeongan stream and livestock excrement in Cheongmi stream is required for water quality improvement of Paldang lake.

Influence of Strong Diurnal Variations in Sewage Quality on the Performance of Biological Denitrification in Small Community Wastewater Treatment Plants (WWTPs)

The great diurnal variation in the quality of wastewater of small communities is an obstacle to the efficient removal of high nitrogen with traditional activated sludge processes provided by pre-denitrification. To verify this problem, the authors developed a pilot plant, in which the domestic wastewater of community of 15,000 inhabitants was treated. The results demonstrate that average and peak nitrogen removal efficiencies of over 60% and 70%, respectively, are difficult to obtain because of the strong variations in the BOD5/NO3-N ratios and the unexpected abnormal accumulation of dissolved oxygen during denitrification when the BOD5 load is low. These phenomena cause inhibitory effects and BOD5 deficiency in the denitrification process. The results demonstrate the need for a more complex approach to designing and managing small wastewater treatment plants (WWTPs) provided with denitrification than those usually adopted for medium- and large-size plants.

Contribution of Non-Point Pollution to Water Quality and Runoff Characteristics from Agricultural Area of the Upstream Watersheds of Lake Chinyang

In this study, non-point source(NPS) contribution was investigated based on flow rates and water qualities of streams into the lake during rainfall events. Event mean concentration(EMC) and the pollution loads were calculated to establish a database for NPS control measurement in the survey area, and so on. The runoff characteristics of NPS were investigated and estimated on the basis of the ratio of an agricultural to forest area in the stream of sub-catch basin during rainfall events. Non-point source pollution loads were also calculated to establish a database for NPS control measure in the upstream lake Chinyang. At a rainfall event, BOD concentrations rise sharply at the early peak time of runoff, however, peaks of TSS concentration were observed at the similar time of peak flow. This was a phenomenon shown at the watersheds caused by forest and geological types. The discharged EMC range was 2.9-4.8 mg/L in terms of BOD. The discharged EMC range was 6.2-8.2 mg/L in terms of SS. The discharged EMCs of T-N and T-P were 1.4-2.5 mg/L and 0.059-0.233 mg/L, respectively. Total BOD loading rate through the 3 tributaries to the lake Chinyang was 1,136 kg/d during dry weather. The upper watershed area of the Nam-river dam in this study was divided into 14 catchment basins based on the Korean guideline for total maximum daily load(TMDL) of water quality pollutants. The higher the agricultural land-use ratio, the more NPS loading rate discharged, but the more occupied a forest area, the lower more NPS loading rate discharged. In an agricultural land-use area more than 20%, the increase of NPS loadings might be dramatically diffused by increasing the integrated complex-use like vinyl-house facilities and fertilizer use etc. according to the effective land-use utilization. The NPS loading rates were BOD 0.3 <TEX>$kg/ha{\cdot}day$</TEX>, SS 0.21 <TEX>$kg/ha{\cdot}day$</TEX>, TN 0.02 <TEX>$kg/ha{\cdot}day$</TEX>, TP 0.005 <TEX>$kg/ha{\cdot}day$</TEX> under less than 10% agricultural land-use. In agricultural land-use of 20%-50%, these values were investigated in the range of 0.32 <TEX>$kg/ha{\cdot}day$</TEX>-0.73 <TEX>$kg/ha{\cdot}day$</TEX> for BOD, 0.92 <TEX>$kg/ha{\cdot}day$</TEX>-3.32 <TEX>$kg/ha{\cdot}day$</TEX> for SS, 0.70 <TEX>$kg/ha{\cdot}day$</TEX>-0.90 <TEX>$kg/ha{\cdot}day$</TEX> TN, 0.03 <TEX>$kg/ha{\cdot}day$</TEX>-0.044 <TEX>$kg/ha{\cdot}day$</TEX> for TP.

下水道整備が陸域の有機物負荷量の長期的な変化に与える影響

This paper evaluated the long-term variations of the input loads of BOD and COD from Akashi river (128.4 km2) and sewerage to the sea using the public water quality observation data set and GIS population and land use analyses. We obtained the following results: 1) BOD and COD input loads from rivers from the late 1970s to 2000s have been reduced by 84% and 69%, respectively, 2) BOD input load from river basin including sewage-treated water has been reduced by 40% from the late 1970s to 2000s, while COD input loads are not reduced (6% increase), 2) BOD and COD input loads were provided 70% by the sewerage and did 30% by the river. These results show the sewage improvement makes the restriction of organic pollution in rivers though the population increased about three times since 1980s.

Energy and sustainability of operation of a wastewater treatment plant

The study summarises the energy consumption data obtained from the Slovak wastewater treatment plants. Overall, 51 large WWTPs using mesophilic anaerobic sludge digestion and biogas utilisation (the total capacity of 2.5 mil. p.e.) and 17 small rural WWTPs (the total capacity 15 000 p.e.) were compared in many technological and energy parameters. The average energy consumption in large WWTPs in Slovakia is 0.485 kWh/m and 0.915 kWh/m in small rural plants. The average energy demand related to BOD5 load represents the value of 2.27 kWh/kg BOD5, in Slovak plants. The specific energy production is relatively low – in average 1.2 kWhel/m of produced biogas and 0.1 kWhel/m of treated wastewater, respectively. The average energy autarky in Slovak plants is 25.2%. Some plants have high energy autarky (>65%), despite no external biowastes being dosed to these during operation.

Rapid monitoring and assessment of pollutional load in dairy waste water

In the present scenario, an attempt was made to develop an ideal device (BOD biosensor) with computer-aided software capable of determining the varying BOD load of dairy waste waters and which facilitates instant monitoring. The shelf life of the developed biosensor was more than 400 days. The results of extensive testing of the developed BOD biosensor on dairy waste water over a period of time demonstrate that the BOD values obtained by the device are statistically correlated with conventional BOD values, irrespective of the varying load of waste water (which might occur as a result of different operations in industry). The developed BOD biosensor shows good reproducibility and repeatability over a period of time. Good correlation (r2 = 0.991) was observed between the values obtained from the developed sensor and conventionally estimated values. The repeatability of the measurements with the BOD biosensor dairy industrial waste water samples (inlet and outlet) was within a percentage deviation of ±10%.

울산지역 상수원 호수 환경에 따른 식물플랑크톤 분포

This study presented the phytoplankton communities of the three lakes (Sayeon, Daeam, Hoeya ) using for drinking water in the Ulsan reservoir. The water storage of the Lake Sayeon, Daeam and Hoeya were 25, 13, 21 million ton respectively and most of which were being utilized for industrial and residential purposes. The total precipitation of the Ulsan region in 2010 was 1,162 mm, decreasing 10 % from 1,275 mm of the annual. As for pollutant loads, BOD and TN discharge loads of Daeam was the highest with 3,277 kg/day, 1,931 kg/day and 90 % of them were came from non-point pollutant sources. TP discharge loads showed the highest in the lake Hoeya with 643 kg/day and 97 % of them were came from point sources as household, industry and livestock. We assessed water quality of the lake Sayeon, Daeam and Hoeya using 17 variables. The water quality assessment found that the lake Daeam met the fourth to fifth grade because of high concentration of COD, SS and chlorophyll-a. Eutrophication assessment was conducted by revised Carlson's Index (TSIm, Aizaki) and found that Lake Daeam was more eutrophicated than the other two lakes all the year through as for chlorophyll-a, transparency and the total phosphorus (TP). A total of 95~111 phytoplankton species were identified from the three lake samples. Among them, the largest number of species were Chlorophyceae with 35~51, followed by Bacillariophyceae with 36~45, Cyanophyceae with 9~11, and Cryptophyceae with 6~9 species. The total cell number of phytoplankton was the highest in February (15,254 cells/mL) with Bacillariophyceae in the lake Daeam and the seasonal succession shows that Bacillariophyceae (Stephanodiscus spp.) in the spring, Cyanophyceae (Anabaena spp.) in the summer and the autumn, Bacillariophyceae (Stephanodiscus spp.) in the winter.

토지피복도 자료원에 따른 대청댐유역 수질특성 비교

This study compared the influence of water quality according to the data sources of spatial information. Firstly, land cover map was constructed through image classification of Daecheong-dam basin and the accuracy of image classification from satellite image showed high as 88.76% in comparison with the large-scaled land cover map in Ministry of Environment, to calculate Event Mean Concentration (EMC) by land cover that impact on the evaluation of nonpoint source pollutant loads. Also curve number and direct runoff were calculated by spatial overlay with soil map and land cover map from image classification. And Seokcheon and Daecheong-Dam basin showed high in the analysis of curve number and direct runoff. Samgacheon-Joint and Sokcheon-Downstream basin showed high in the nonpoint source pollutant loads of BOD from direct runoff and EMC. And Samgacheon-Joint and Bonghwangcheon- Downstream basin showed high in the nonpoint source pollutant loads of TN and TP. Nonpoint source pollutant loads from image classification were compared with those by the land cover map from Ministry of Environment to present the effectivity of nonpoint source pollutant loads from satellite image. And Daecheong-Dam Upstream basin showed high as 10.64%, 11.70% and 20.00% respectively in the errors of nonpoint source pollutant loads of BOD, TN, and TP. Therefore, it is desirable that spatial information including with paddy and dry field is applied to the evaluation of nonpoint source pollutant loads in order to simulate water quality of basin effectively.

Recovery of Polyvinyl Alcohol from Desizing Wastewater Using a Novel High‐Shear Ultrafiltration Module

AbstractPolyvinyl alcohol (PVA), the major constituent of desizing water constituting 45% of the total BOD load has a significant environmental impact owing to its poor biodegradability. In order to prevent PVA from being discharged by the effluent stream, modern textile industries opt for membrane based separation techniques using ultrafiltration so that the recovery and recycle of PVA in tandem could be achieved. However, the process of ultrafiltration is still not widely accepted as expected due to the well‐known non‐idealities of concentration polarization and pore blockage. In this article, design and performance characterization of a lab‐scale novel shear enhanced ultrafiltration unit, named as spinning basket membrane (SBM) module are discussed. The proposed module is unique in terms of its inbuilt cleaning facility eliminating the effects of polarization and subsequent periodic fouling leading to its uninterrupted production operation. The test fluid, necessarily a solution of PVA was treated in the proposed module under different parametric conditions with polyvinylidene fluoride (PVDF) membranes of two different molecular weight cut‐off (50 and 100 kDa). After 2 h of continuous operation the permeate flux was observed to be within 95–97% of the respective initial fluxes. Such performance is rarely been attained in practice. Hence, the novelty of the present research is achieved. Considering the performance of the present module in terms of flux regeneration and product recovery, it may be regarded as an efficient device and can be potentially deployed for cleaning of other industrial wastewater.

TMDL 지원을 위한 QUAL2E 모델을 이용한 GIS기반의 삭감시나리오 작성 지원시스템 개발에 관한 연구

Abstract : This study was mainly focused on the development of GIS based decision support system to easily make mitigation scenarios and to conveniently simulate water quality for TMDL. The study area was the 31km section of upper Sapgyo stream in Geum river basin, and QUAL2E model was adopted. GIS DB was built through the collection of the data which includes point/ non-point source attributes and various thematic maps. The amounts of discharged loads of BOD, T-N and T-P from unit watershed were estimated respectively. Finally, the system, which can operate water quality simulation through simply modifying their values, was developed. The hypothetical three mitigation scenarios were applied, thereby the most efficient mitigation scenario could be chosen by comparison of the results based on GIS. Therefore, it is expected that the developed system can facilitate the decision makers to select the best alternative through the analysis of the available BMPs. Also, it can be used to develop new scenarios using different methods and algorithms. In the future, more study need to be made to enhance its applicability in the perspective of developing mitigation scenarios through the management of individual pollutant sources and extending study areas.

Validation of MIKE 11 Model Simulated Data for Biochemical and Chemical Oxygen Demands Transport

The aim of the study was to model the discharge, biochemical and chemical oxygen demands (BOD and COD) loads in each cross section of Bertam River in Cameron Highlands, Malaysia. Cameron Highlands form the headwater catchment for two major rivers of the lowlands; Pahang River and Perak River. On the other hand, Cameron Highlands is undergoing rapid development as a popular tourist destination and an area exploited for growing of temperature vegetables, fruits and flowers. It is also a mountainous area subjected to torrential tropical showers. The condition of Bertam River as one of the main rivers in Cameron Highlands has degraded over the years in terms of water pollution and river environment. Approach: Therefore, MIKE 11 a onedimensional hydrodynamic simulation program was utilized to model stream flow transport and water quality processing in the river system. The model was used to generate the river outflow and simulate BOD and COD concentrations in each cross section of Bertam River. Hydrodynamic Module (HD) which uses an implicit, finite difference solver was applied to calculate water level and flow for the river. Next, Rainfall-Runoff Module (RR) which is include unit hydrograph method and lumped conceptual continuous hydrological model was used to combine the meteorological data of the study area to MIKE 11 simulation system. Finally, Advection-Dispersion Module (AD) was used for transported BOD and COD concentrations calculation. Results: Water quality results show the BOD5 varies from 1-2 mg L-1 during pre-monsoon and from 4-10 mg L-1 during post-monsoon. The COD between 39-49 mg L-1 was observed during High Water Flow (HWF). Much lower concentration was detected during Average Water Flow (AWF) which was between 10-14 mg L-1. The comparative analysis between measured and simulated data showed that MIKE 11 is able to predict sufficiently accurate BOD and COD loads at the catchment outlet especially during AWF. Conclusion: Due to higher discharge during HWF some differences between measured and predicted values were observed. Therefore, it is suggested that for better agreement at higher discharges the hydraulic model simulation to be conducted using more measured flow data and by application of more precise differential equation such as RKQC and RK4.

A study on olive oil mill wastewater management in Turkey: A questionnaire and experimental approach

The purpose of this study is to provide profound information about olive oil mill wastewater production in Turkey and to evaluate and optimize the treatment of olive oil mill wastewater (OOMW) by using slow rate land treatment system. Within the scope of the study, about 150 olive oil industries located in the west and south of Turkey were examined by means of a questionnaire survey. The results showed that high percentage of producers in Turkey use three-phase centrifugation generating high amount of wastewater. The use of large evaporation ponds is the common treatment technology for the “reduction” of the wastewater. For the experimental part of the study, nine 65-liter PVC reactors were constructed and operated outside the laboratory. Reactors containing 55kg of sandy-loam soil were planted by Reed (phragmites) and Alfalfa (alphalpha sp.) species and irrigated with olive oil mill wastewater having the same organic loading but different hydraulic loading rate. BOD5 loading rate was 500kgBOD5/haday and hydraulic loading rates were 2, 4, 8 and 12.5m/year. Hydraulic loading is later fixed to 4m/year and organic loading is changed to 125, 250 and 500kgBOD5/haday during the second year. The results of the experiments indicated that COD removal rates were initially high in reactors with plants compared to control reactor without plant. However, the rates decreased in time due to the inhibition observed in the treatment capacity of the combined system.

여자만의 수질관리를 위한 허용유입부하량 산정

여자만은 유기물 오염이 점차 진행되어 가고 있으며, 해역의 수질관리를 위하여 유역으로부터 유입하는 육상기인 오염물질을 GIS 기법을 이용하여 발생부하량과 배출부하량을 산정하였다. 목표수질을 달성하기 위해 해역의 환경용량을 초과하여 유입하는 육상오염물질의 양을 박스모델로 계산하여 삭감부하량과 허용유입부하량을 평가하였다. 여자만의 수질을 해역생활환경기준 I등급으로 회복하기 위한 허용부하량을 산정한 결과, 생물화학적산소요구량은 배출부하의 39.3%, 총인은 30.8%를 삭감해야 하고, 총질소의 경우 6.9%의 낮은 배출부하 삭감률을 나타내었다. 유역의 오염원 현황과 발생부하량 현황을 볼 때 토지계가 차지하는 오염부하 비중이 높고, 배출부하량에서도 가장 큰 비중을 차지하였다. 여자만의 해양환경 보호와 개선을 위해서는 육상기원 오염물질 중 점오염원 뿐만 아니라 축산계 및 토지계 부하 등 비점원 오염원에 대한 관리가 필요하다는 것을 시사한다. Based on the consideration of land based pollutant discharges from the basin and seawater quality related carrying capacity and the seawater quality improvement in receiving water bodies of Yeoja Bay where eutrophication and organic pollution are in progress, were evaluated. The permissible inflow loads of BOD, TN and TP by using the geographical features and box modelling method were estimated. As results, it is shown that the reduction rate of discharged BOD and TP loads were 39.3% and 30.8 %, respectively, however, 6.9% was estimated for TN. According to the pollutant loading in each tributary and generated load of the basin, it is given much weight on the land use group, and also was shown in discharged load estimation. This suggests that it is important to control nonpoint source pollutant such as livestock and land use groups as well as point source to contribute the proposition of the water quality improvement plan according to the characteristics of the bay.

Woven Fabric Bioreactor (WFBR) as the Filter Material for Wastewater Treatment

Conventional and modified membrane bioreactors (MBRs) are effective increasingly used in small sized wastewater treatment plant. However, their widespread applications are hindered by their elevated energy consumption and the high costs of investment for the membrane modules. In this study, we investigated a modified an improved MBR system that utilized a cost effective woven fabric instead of nonwoven as the filter material in MBR modules. The woven fabric bioreactor (WFBR) system was operated in a continuous mode at HRT from 33 to 12h. Under the operational conditions of BOD loading rates from 0.12 to 0.28 kg BOD/kg MLSS /d, the WFBR system was able to reduce up 93.57% COD. The 38μm woven fabric performed well in solid-liquid separator, with an average suspended solids retention of 99.47% at MLSS of 4710~9951 mg/L. The WFBR system eliminated suction pumping by using a gravity head in the membrane filtration of the effluent over the entire operational period of 60 d.

Effect of initial MLSS on operation of submerged membrane activated sludge process

The submerged membrane activated sludge processes were examined for application to the septic tank. The bench scale experiments of this process were carried out at various initial MLSSs under volumetric BOD loadings ≈ 0.50kq/(m3·d) without withdrawal of the mixed suspended liquid. The average MLSS conversion ratio of this process was about 0.2kg-MLSS/kg-BOD, which was about 33% of that for a conventional activated sludge process. When the initial MLSS is very low (high F/M ratio), the supernatant TOC was high and the organic matters in influent could not be degraded completely, and the suction pressures fluctuated greatly. When the initial MLSS is very high, suction pressures increased rapidly after intermediate treatment time due to high MLSS in the bioreactor. Therefore a long-term stable operation could not be performed in low and high initial MLSS, and could be done in moderate initial MLSS (about 3000–5000mg/L).

Technical challenges with BOD/DO modeling of rivers in Taiwan

Many rivers and streams in Taiwan receive significant BOD and ammonia loads from domestic and industrial wastewaters. These loads are characterized by excessive strength (high concentrations and wastewater flows) – often with great spatial intensity. In many cases, an additional significant load enters the stream before the upstream input is fully stabilized in the receiving water. The classic DO sag and recovery curve in rivers associated with single point source BOD loads (as found in most textbooks) are therefore rare in Taiwan’s rivers. As a result, a different modeling approach must be adopted to address technical challenges associated with modeling for water quality management in Taiwan. In this paper, the modeling results of two rivers in Taiwan are presented to demonstrate the associated technical issues and difficulties, as well as recommend further effort to meet these challenges.

Evaluation of a lab-scale tidal flow constructed wetland performance: Oxygen transfer capacity, organic matter and ammonium removal

Oxygen transfer capacity and removal of ammonium and organic matter were investigated in this study to evaluate the performance of a lab-scale tidal flow constructed wetland. Average oxygen supply under tidal operation (350 g m −2 d −1) was much higher than in conventional constructed wetlands (<100 g m −2 d −1), resulting in enhanced removal of BOD 5 and NH 4 +. Theoretical oxygen demand from BOD 5 removal and nitrification was approximately matched by the measured oxygen supply, which indicated aerobic consumption of BOD 5 and NH 4 + under tidal operation. When BOD 5 removal increased from 148 g m −2 d −1 to 294 g m −2 d −1, neither exhausted oxygen from the aggregate matrix during feeding period (111 g m −2 d −1) nor effluent dissolved oxygen (DO) concentration (2.8 mg/L) changed significantly, demonstrating that the oxygen transfer potential of the treatment system had not been exceeded. However, even though DO had not been exhausted, inhibition of nitrification was observed under high BOD loading. The loss of nitrification was attributed to excessive heterotrophic biofilm growth believed to induce oxygen transfer limitations or oxygen competition in thickened biofilms.

INDUSTRIAL WASTEWATER TREATMENT AND ITS IMPACT ON WATER QUALITY"CASE STUDY

Ceramic industry wastewaters not only contain high total suspended solids but also significant amounts of dissolved organics resulting in high BOD or COD loads. Suspended solids can be removed from the wastewater by chemical precipitation. However, dissolved BOD/COD compounds can only be removed by biological or chemical oxidation.