水质生物毒性预警系统建设及在海宁市饮用水源保护中的应用

介绍了基于微生物燃料电池原理的水质生物毒性预警系统,说明了其在海宁市饮用水源保护中的应用。该水质生物毒性预警系统具有可感知毒性物质及有机物质污染、响应迅速、灵敏度高、维护管理容易、管理费用低等特点。     

焦化废水生化处理过程中溶解性有机物及毒性变化规律

焦化废水中的溶解性有机物(DOM)作为废水污染物和毒性的主要来源受到广泛关注。厌氧-缺氧-好氧(A-A-O)生物法联合混凝沉淀工艺在焦化废水处理中被广泛应用。于2018年4,7和11月分别采集4座焦化废水处理厂废水,采用光谱学分析手段和水生生物急性毒性试验对A-A-O联合混凝沉淀处理过程中焦化废水的DOM和毒性变化进行分析。结果表明,焦化废水中含有大量不饱和芳香性物质,其中类色氨酸、络氨酸物质占主导,其次为类溶解性微生物代谢产物、类富里酸物质和类腐殖酸类物质;未经处理的焦化废水对藻类和大型溞的急性毒性等级为中毒至高毒。A-A-O联合混凝沉淀处理可去除90%以上的类色氨酸、络氨酸和类富里酸物质,但对类腐殖酸类物质去除率相对较低,仅为约80%,关键去除段为缺氧段和好氧段;该工艺对焦化废水急性毒性削减率为80.51%~94.30%,关键削减段为厌氧段。Pearson相关性分析结果显示,焦化废水溶解性总有机碳(TOC)、类腐殖酸类物质荧光组分C1和类富里酸类物质荧光组分C4与废水急性毒性存在显著正相关关系,可利用其作为水样急性毒性初筛的指示性指标。可为焦化废水生化处理的效能优化和废水毒性控制及安全评估提供科学支撑。     

Practical field application of a novel BOD monitoring system

A biochemical oxygen demand (BOD) monitoring system, based on electrochemically-active bacteria in combination with a microbial fuel cell, has been developed for the purpose of on-site, on-line and real-time monitoring of practical wastewater. A microbial fuel cell that had been enriched with electrochemically-active bacteria was used as the basis of the measurement system. When synthetic wastewater was fed to the system, the current generation pattern and its Coulombic yield were found to be dependent on the BOD5 of the synthetic wastewater. A linear correlation between the Coulombic yields and the BOD5 of the synthetic wastewater were established. Real wastewater obtained from a sewage treatment plant also produced a highly linear correlation between the Coulombic yield and BOD5 in the system. To examine on-site, on-line and real-time monitoring capability, the BOD monitoring system was installed at a sewage treatment plant. Over 60 days, the measurement system was successfully operated with high accuracy and good stability with the measuring period for a sample being 45 min. This application showed that the application of the measurement system was a rapid and practical way for the determination of BOD5 in water industries.     

A 300 year history of lead contamination in northern French Alps reconstructed from distant lake sediment records

Lead concentrations and isotopic ratios were measured along two well-dated sediment cores from two distant lakes: Anterne (2100 m a.s.l.) and Le Bourget (270 m a.s.l.), submitted to low and high direct human impact and covering the last 250 and 600 years, respectively. The measurement of lead in old sediment samples (>3000 BP) permits, in using mixing-models, the determination of lead concentration, flux and isotopic composition of purely anthropogenic origin. We thus show that since ca. 1800 AD the regional increase in lead contamination was mostly driven by coal consumption ((206)Pb/(207)Pb approximately 1.17-1.19; (206)Pb/(204)Pb approximately 18.3-18.6), which peaks around 1915 AD. The increasing usage of leaded gasoline, introduced in the 1920s, was recorded in both lakes by increasing Pb concentrations and decreasing Pb isotope ratios. A peak around 1970 ((206)Pb/(207)Pb approximately 1.13-1.16; (206)Pb/(204)Pb approximately 17.6-18.0) corresponds to the worldwide recorded leaded gasoline maximum of consumption. The 1973 oil crisis is characterised by a drastic drop of lead fluxes in both lakes (from approximately 35 to <20 mg cm(-2) yr(-1)). In the late 1980s, environmental policies made the Lake Anterne flux drop to pre-1900 values (<10 mg cm(-2) yr(-1)) while Lake Le Bourget is always submitted to an important flux (approximately 25 mg cm(-2) yr(-1)). The good match of our distant records, together and with a previously established series in an ice core from Mont Blanc, provides confidence in the use of sediments as archives of lead contamination. The integration of the Mont Blanc ice core results from Rosman et al. with our data highlights, from 1990 onward, a decoupling in lead sources between the high elevation sites (Lake Anterne and Mont Blanc ice core), submitted to a mixture of long-distance and regional contamination and the low elevation site (Lake Le Bourget), where regional contamination is predominant.     

Comparison of TCPP concentrations in sludge and wastewater in a typical German sewage treatment plant-comparison of sewage sludge from 20 plants

Tris(chloro-isopropyl)phosphate (TCPP) was identified by GC-MS by comparing mass spectra and retention times to original standards. The concentrations in wastewater of a sewage treatment plant's influent and effluent were analysed (520 ng l(-1) and 380 ng l(-1), respectively (mean values). The concentrations of TCPP in the wastewater inflow exhibited a high variability. The elimination of this compound in the sewage treatment plant also exhibits a high variability but is low. Additionally the concentrations in sewage sludge of the same plant were determined (mean value 5100 ng g(-1) dry weight; 1700 ng g(-1) wet weight, respectively). For a comparison sludge samples from twenty other plants were analysed. In these samples concentrations ranging from 1000-20000 ng g(-1)(dry weight) were determined. Thus sorption to sludge does occur to some extent.     

Blood biomonitoring of metals in subjects living near abandoned mining and active industrial areas

A human blood biomonitoring campaign to detect the environmental exposure to metals (Cd, Cu, Cr, Mn, Pb and Zn) in 265 subjects was performed in the South-Western part of Sardinia (an Italian island) that is a particular area with a great history of coal and metal mining (Pb/Zn mainly) activities and large industrial structures (as metallurgy). Subjects living near the industrial plant area had geometric means (GM) of blood Cd (0.79 μg/l), Cu (971 μg/l), Mn (12.2 μg/l), and Pb (55.7 μg/l) significantly higher than controls (Cd, 0.47 μg/l; Cu, 900 μg/l; Mn 9.98 μg/l; Pb, 26.5 μg/l) and than people living nearby the past mining sites. Subjects living next to one dismissed mine were statistically higher in blood Cu (GM, 1,022 μg/l) and Pb (GM, 41.4 μg/l) concentrations than controls. No differences were observed in people living in the different mining sites, and this might be related to the decennial disclosure of mines and the adoption of environmental remediation programmes. Some interindividual variables influenced blood biomonitoring data, as smoke and age for Cd, gender for Cu, age, sex and alcohol for Pb, and age for Zn. Moreover, blood metal levels of the whole population were similar to reference values representative of the Sardinian population and acceptably safe according to currently available health guidelines.     

Determination of six anti-infectives in wastewater using tandem solid-phase extraction and liquid chromatography-tandem mass spectrometry

A rugged and specific method based on tandem solid-phase extraction and liquid chromatography-tandem mass spectrometry for the determination of anti-infectives in raw sewage and wastewater plant effluents was developed. Analyte recoveries from spiked effluents ranged from 68 to 104%. Two specific selected reaction monitoring transitions and their peak area ratios were used to avoid false positives and confirm the presence of the targeted substances. Detection limits allowed low nanogram per litre detection (0.3-22 ng L(-1)). The method was successfully applied to real samples from the Montréal wastewater treatment plant. All the studied anti-infectives were found in the wastewater samples in concentrations ranging from 39 to 276 ng L(-1). Mean flows of anti-infectives were estimated from effluent concentrations and it was found that large amounts (>118 g day(-1) up to 830 g day(-1)) are discharged in the receiving waters of the St Lawrence River.     

Inventory compilation and distribution of heavy metals in wastewater from small-scale industrial areas of Delhi, India

Delhi has the highest cluster of small-scale industries (SSI) in India. There are generally less stringent rules for the treatment of waste in SSI due to less waste generation within each individual industry. This results in SSI disposing of their wastewater untreated into drains and subsequently into the river Yamuna, which is a major source of potable water in Delhi, thus posing a potential health and environmental risk to the people living in Delhi and downstream. To study the quantity, quality and distribution of heavy metals in liquid waste from industrial areas, wastewater, suspended materials and bed sediments were collected from industrial areas and from the river Yamuna in Delhi. This study has also focused on the efficiency of production processes in small-scale industries in India. Heavy metals such as Fe, Mn, Cu, Zn, Ni, Cr, Cd, Co and Pb were detected using a GBC 902 atomic absorption spectrometer. The concentration of heavy metals observed was as follows: Fe 2-212, Mn 0.3-39, Cu 0.2-20, Zn 0.2-5, Ni 0.6-6, Cr 0.2-53, Cd 0.08-0.2, Co 0.013-0.55, Pb 0.3-0.7 mg L(-1) in wastewater; Fe 5842-78 000, Mn 585-10 889, Cu 206-7201, Zn 406-9000, Ni 22-3621, Cr 178-10 533, Co 17-114, Cd 13-141, Pb 67-50 171 mg kg(-1) in suspended material; and Fe 3000-84000, Mn 479-1230, Cu 378-8127, Zn 647-4010, Ni 164-1582, Cr 139-3281, Co 20-54, Cd 37-65, Pb 228-293 mg kg(-1) in bed residues. This indicates that SSI could be one of the point sources of metals pollution in the river system.     

SEC-ICP-MS studies for elements binding to different molecular weight fractions of humic substances in compost extract obtained from urban solid waste

In this work, the speciation of elements in compost was studied with emphasis on their binding to humic substances. In order to assess the distribution of As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, U, Th and Zn among molecular weight fractions of humic substances, the compost extract (extracted by 0.1 mol l(-1) sodium pyrophosphate) was analyzed by size exclusion chromatography coupled on-line with UV-Vis spectrophotometric and ICP-MS detection. Similar chromatograms were obtained for standard humic acid (Fluka) and for compost extract (254 nm, 400 nm) and three size fractions were operationally defined that corresponded to the apparent molecular weight ranges > 15 kDa, 1-15 kDa and < 1 kDa. The percentage of total element content in compost that was leached to the extract ranged from 30% up to 100% for different elements. The elution profiles of Co, Cr, Cu, Ni and Pb (ICP-MS) followed that of humic substances, while for other elements the bulk elution peak matched the retention time observed for the element in the absence of compost extract. Spiking experiments were carried out to confirm elements' binding and to estimate the affinity of individual elements for humic substances derived from compost. The results obtained indicated the following order of decreasing affinity: Cu > Ni > Co > Pb > Cd > (Cr, U, Th) > (As, Mn, Mo, Zn). After standard addition, further binding of Cu, Ni and Co with the two molecular weight fractions of humic substances was observed, indicating that humic substances derived from compost were not saturated with these elements.     

Toxic effect caused on microflora of soil by pesticide picloram application

The toxic effect of the herbicide picloram on the microbial population of a typical Brazilian red Latosol soil was studied in a series of microcalorimetric experiments. The activity of the soil was stimulated by the addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate, under 34.8% controlled moisture, to a 1.50 mg soil sample, at 298.15 +/- 0.02 K. The net thermal effect due to the addition of the picloram to the soil was determined by interpreting the power-time curves, which were recorded on the microcalorimeter. The total thermal effect evolved by the microorganisms was affected by the increasing doses of herbicide, and varied from 0 to 10.00 micrograms g-1. An increase in picloram exposure caused a decrease of the original thermal effect, reaching a null value above 20.89 micrograms of herbicide per gram of soil. The decreases of the thermal effect evolved by microorganisms and the increase of the lag phase period are associated with the death of the microbial population. The effects caused by picloram application in this typical Brazilian soil resulted in a strong effect on the soil microbial communities.     

Element contents and food safety of water spinach (Ipomoea aquatica Forssk.) cultivated with wastewater in Hanoi, Vietnam

Extensive aquatic or semi-aquatic production of water spinach (Ipomoea aquatica Forssk.) for human consumption takes place in Southeast Asia. The aim of this study was to assess the concentrations of 38 elements in soil and water spinach cultivated under different degrees of wastewater exposure in Hanoi, Vietnam. The results showed no effect of wastewater use on the overall element concentrations in soil and water spinach. Mean soil concentrations for selected potentially toxic elements at the studied field sites had the following ranges 9.11–18.7 As, 0.333–0.667 Cd, 10.8–14.5 Co, 68–122 Cr, 34.0–62.1 Cu, 29.9–52.8 Ni, 32.5–67.4 Pb, 0.578–0.765 Tl and 99–189 Zn mg kg⁻¹ dry weight (d.w.). In all samples Cd, Pb and Zn soil concentrations were below the Vietnamese Guideline Values (TCVN 7209-2002) for agricultural soils whereas As and Cu exceeded the guideline values. Maximum site element concentrations in water spinach were 0.139 As, 0.032 Cd, 0.135 Cr, 2.01 Cu, 39.1 Fe, 57.3 Mn, 0.16 Ni, 0.189 Pb and 6.01 Zn mg kg⁻¹ fresh weight (f.w.). The site and soil content of organic carbon were found to have high influence on the water spinach element concentrations whereas soil pH and the total soil element concentrations were of less importance. The estimated average daily intake of As, Cd, Cu, Fe, Pb and Zn for adult Vietnamese consumers amounts to <11% of the maximum tolerable intake proposed by FAO/WHO for each element. It is assessed that the occurrence of the investigated elements in water spinach will pose low health risk for the consumers.     

Metal immobilization and phosphorus leaching after stabilization of pyrite ash contaminated soil by phosphate amendments

In this study we would like to show the importance of a holistic approach to evaluation of chemical stabilization using phosphate amendments. An extensive evaluation of metal stabilization in contaminated soil and an evaluation of the leaching of phosphorus induced after treatment were performed. The soil was highly contaminated with Cu (2894 mg kg(-1)), Zn (3884 mg kg(-1)), As (247 mg kg(-1)), Cd (12.6 mg kg(-1)) and Pb (3154 mg kg(-1)). To immobilize the metals, mixtures of soil with phosphate (from H(3)PO(4) and hydroxyapatite (HA) with varying ratios) were prepared with a constant Pb : P molar ratio of 1: 10. The acetic acid extractable concentration of Pb in the mixture with the highest amount of added phosphoric acid (n(H(3)PO(4)) : n(HA) = 3 : 1) was reduced to 1.9% (0.62 mg L(-1)) of the extractable Pb concentration in the untreated soil, but the content of water extractable phosphorus in the samples increased from 0.04 mg L(-1) in the untreated soil sample up to 14.3 mg L(-1) in the same n(H(3)PO(4)) : n(HA) = 3 : 1 mixture. The high increase in arsenic mobility was also observed after phosphate addition. The PBET test showed phosphate induced reduction in Pb bioavailability. In attempting to stabilize Pb in the soil with the minimum treatment-induced leaching of phosphorus, it was found that a mixture of soil with phosphate addition in the molar ratio of H(3)PO(4) : HA of 0.75 : 1 showed the most promising results, with an acetic acid extractable Pb concentration of 1.35 mg L(-1) and a water extractable phosphorus concentration of 1.76 mg L(-1). The time-dependent leaching characteristics of metals and phosphorus for this mixture were evaluated by a column experiment, where irrigation of the soil mixture with the average annual amount of precipitation in Slovenia (1000 mm) was simulated. The phosphorus concentration in the leachates decreased from 2.60 mg L(-1) at the beginning of irrigation to 1.00 mg L(-1) at the end.     

Assessment of Treatment Alternatives for Laboratory COD Wastewater: a Practical Comparison with Emphasis on Cost and Performance

This study focused on investigation of treatment alternativesfor COD wastewater from academic laboratories, using a number oftechnologies including chemical reduction/precipitation, ion exchange and adsorption by chitosan. Results showed that highconcentrations of 375 mg l^-1 chromium, 1,740 mg l^-1mercury and 993 mg l^-1 silver in COD wastewater can be reduced to 2.34 mg l^-1, 3.65 mg l^-1 and 1.89 mg l^-1 respectively, by the chemical reduction/precipitationprocess. Results from ion exchange at a flowrate of 20 ml min^-1 showed breakthrough effluent concentrations obtainedat 0.59 mg l^-1 chromium, 3.92 g l^-1 mercury and 0.65 mg l^-1 silver corresponding to 75.6 l at 63 hr, 40.8 l at 34 hr and 33.6 l at 28 hr respectively. Kinetic and isotherm studies revealed that chitosan can adsorb Cr⁶⁺, Hg²⁺ and Ag⁺ ions most effectively at a flowrate of 20 ml min^-1 and the optimum pH for feed solution is 4. Chitosan column experiments indicated that average effluent concentrations at breakthrough point for chromium, mercury andsilver are 0.76 mg l^-1, 6.04 mg l^-1 and 0.51 mg l^-1 respectively with throughput volumes and retention times of 120 l at 100 hr, 60 l at 50 hr and 48 l at 40 hr. Results of solidification experiments for chemical sludge and residual chitosan based on compressive strength and metal leachabilitytests showed, that the acceptable ranges of the solidificationparameters were: sludge/cement = 0.1–1.0 (weight/weight), water/cement = 0.5–0.6 (weight/weight) and sand/cement = 0.5–3.0 (weight/weight). Operating cost per litre of COD wastewater treated, based on the current prices in Thailand wasfound to be Baht 19.95 for the chemical reduction/precipitationprocess, Baht 96.35 for ion exchange treatment and Baht 18.29 forchitosan adsorption.     

Kinetics of Biotransformation of 2,4-Dichlorophenol using UASB-Reactor

Chlorophenol compounds are environmental pollutants that are both anthropogenic and xenobiotics. Some of these chemicals are carcinogens and are both toxic to a number biochemical processes. Biotransformation of 2,4-dichlorophenol (2,4-DCP) was studied in the presence of glucose on an upflow anaerobic sludge blanket reactor (UASB) using mixed culture. A continuously operated UASB reactor was employed using mixed synthetic wastewater. Results obtained from the 1.8 L volume capacity UASB reactor were subjected to kinetic evaluation constants. Results indicate that the degradation of 2,4-DCP in the presence of glucose was strongly influenced by the concentration of the compound. High degradation levels were observed when the concentration of 2,4-DCP was in the range of 50-150 mg L(-1). Concentrations of 2,4-DCP above 160 mg L(-1) were toxic to microbes even in the presence of glucose. The maximum degradation of 2,4-DCP was found to be 70.4% when initial concentration of 2,4-DCP was 124 mg L(-1) and glucose concentration of 500 mg L(-1) at hydraulic retention time of 13.2 hr. The biodegradation followed first order reaction kinetics with a rate constant (K) of 0.67, Vmax of 0.244 kg m(-3) day(-1), Ks of 0.117 kg m(-3) day(-1) and correlation coefficient of 0.766.     

Seasonal variation of different microorganisms with nickel and cadmium in the industrial wastewater and agricultural soils

Wastewater and soil samples were collected from the industrial area of Ghaziabad City, India from January 2005 to December 2007 and were analyzed for the presence of heavy metals by atomic absorption spectrophotometry. Test samples revealed high levels of Fe, Cr, Cu, Ni, Zn, and Cd as 967.03, 34.63, 27.97, 19.7, 16.70, and 3.20 mg/L of wastewater, respectively. The concentrations of inorganic minerals were higher in the soil samples irrigated with wastewater. Total coliforms were found to be maximum (1,133 × 10⁴ most probable number per 100 mL) during spring and summer followed by winter and postmonsoon in the wastewater samples. The microbial count in soil as well as in wastewater decreases as the metal concentration increases. The concentration 200 μg/mL of nickel and cadmium inhibits majority of the population, while, at some points, it inhibits 100% of the population. The exponential decay model for microbial count at the increasing metal concentrations indicate that asymbiotic N₂ fixers were best fitted to the model. In all the seasons, the order of decline in terms of exponential decay of the population of different microbial groups in soil was asymbiotic N₂ fixers > actinomycetes > fungi > aerobic heterotrophic bacteria. The different microbial groups that have different values of slope in different seasons indicate that the resistant population of microorganisms was variable with seasons.     

The Asiatic clam,Corbicula spp., as a biological monitor in freshwater environments

Asiatic clams, Corbicula spp., are filter-feeding freshwater bivalves that are widely distributed, abundant, and fast growing with a lifespan of 1–3 yrs. A review of the existing literature demonstrates that Asiatic clams can concentrate organic pollutants from both water and sediment and heavy metals from water. In conjunction with these traits, they exhibit a high tolerance for the effects resulting from exposure to toxic substances. While an organism must possess these traits to serve as an effective biological monitor, they have also permitted the Asiatic clam to rapidly colonize natural and industrial environments resulting in purported ecological disturbances and severe economic repurcussions, respectively. Its invasive biofouling attributes therefore restrict the use of Asiatic clams for biomonitoring purposes from Corbicula-free drainage systems.     

液相色谱-串联质谱法同时测定污水中10种精神活性物质

建立了采用液相色谱-串联质谱法(LC-MS/MS)同时测定污水中10种精神活性物质的分析方法。污水样品经甲酸与甲酸铵调节pH后,加入氘代内标混匀,离心并过滤膜后可直接上样分析。研究表明,在1~250 ng/L的线性范围内,10种精神活性物质的线性相关系数均大于0.992,定量限均低于0.5 ng/L。在3个加标水平下,10种精神活性物质的加标回收率为87.2%~114%,相对标准偏差为0.53%~3.60%(n=3)。将该方法应用于某区域10份生活污水样品的检测,在3份水样中检出吗啡、甲基苯丙胺、氯胺酮等精神活性物质,对应的质量浓度范围分别为3.41~9.55、0.90~1.63、1.06~1.78 ng/L。与经固相萃取前处理后的分析方法相比,该方法可在10 min内完成分离和检测的全过程,具有简单、快速、节约的优点,可用于污水样品中10种痕量水平精神活性物质的定量分析。     

毒性废水稀释中强度改变与浓度改变的跟随性研究

适用于已知毒物和毒性应用剂量测定的经典技术方法，以样品稀释过程中毒性强度改变与浓度改变的等比率跟随性为基础。废水中的毒性物质常以未知和混合为特征，高毒性的样品现状浓度距离方法预试验中最小全致死浓度较远，以已知毒物重铬酸钾毒性为对照，形成5种毒物高层级等强度毒性，通过这些高毒性废水同步等比率稀释后毒性改变的同步性测定试验，证明毒性废水稀释中强度改变与浓度改变的跟随状态具有不确定性。     

Influence of paint chips on lead concentration in the soil of public playgrounds in Tokyo

Lead concentration in the surface soils from 31 playgrounds in a ward in Tokyo was measured to examine if paint chips, peeled off from playing equipment installed in the playgrounds, contribute to elevated Pb concentration in the soil of public playgrounds. Lead concentration in the paint chips sampled from playgrounds ranged from 0.003 to 8.9%. Lead concentration in the surface soil ranged from 15.2 to 237 mg kg(-1) (average, 55.5 mg kg(-1)) and higher Pb concentration was found in the soil near painted playing equipment indicating that paint chips from playing equipment contributed to increase soil Pb level of playgrounds in Tokyo. The degree of peeling-off of paint on the surface of playing equipment in the public playground (peeling-off index: POI) positively correlated with Pb concentration in the soil (Spearman rank-correlation coefficient, r = 0.366, p = 0.043). The stronger correlation between Pb concentration and isotope ratios (207Pb/206Pb and Pb conc., r = 0.536, p = 0.002, 208Pb/206Pb and Pb conc. r = 0.600, p < 0.001) than that between Pb and POI indicated that gasoline Pb contributed more to the playground-to-playground variation in soil Pb concentration. It was concluded that both gasoline Pb of the past and paint chips contributed to increased Pb concentration in the surface soil of playgrounds in Tokyo, though the contribution of paint chips is smaller than gasoline Pb.     

Effects of land use and municipal wastewater treatment changes on stream water quality

This study was undertaken to analyze the quantitative impact of a municipal wastewater treatment operation on the long-term water quality changes in a tributary of the Han-river, Korea from 1994 to 1999. Changes of land use pattern in the study watershed are quantitatively analyzed on the basis of land use maps that were created by classifying Landsat TM images acquired in April 1994 and March 1999. During this period, the average increase of land use area in terms of residence, cultivation, and barren was 5.89, 0.13, and 0.12%, respectively, and the corresponding decrease in water and forest area was 0.21 and 0.16%. The annual average reductions of BOD, T-N, and T-P by the municipal wastewater treatment operation were about 89, 11 and 27%, respectively. Spatial analysis of the pollution discharge from watershed was undertaken using a geographic information system (GIS) based model. A clear reciprocal relationship was found between the basin-wide self-purification coefficient and the watershed form ratio excepting a catchment area with water drain facilities. Due to land use changes over the five year study period, water quality change in terms of BOD, T-N, and T-P were (+)1.04 mg l(-1) (corresponding to a 13.7% increase of pollution), (+)0.58 mgl(-1) (10.0% increase), and (-)0.01 mg l(-1) (1.6% decrease). On the other hand, the effect of water quality restoration assessed by outward appearance during the same period was about 67.6, 39, and 36.5%, respectively. Consequently, it is understood that total stream water quality recovery in terms of BOD, T-N, and T-P were 81.3, 49.0, and 38.1% respectively, and that this included a negative contribution resulting from increased land use and a positive contribution due to the wastewater treatment operation at Inchon.