Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

Assessment of Nitrogen Pollutant Sources in Surface Waters of Taihu Lake Region

The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.

Genotoxicity evaluation and a primary risk assessment of organic pollutants in the drinking water sources of Nanjing, China

An increasing number of industrial, agricultural, and commercial chemicals in the aquatic environment leads to various deleterious effects on organisms, which is becoming an increasingly serious problem in China. In this study, the comet assay was conducted to investigate the genotoxicity to human body caused by organic concentrates in the drinking water sources of Nanjing City from Yangtze River of China, and health and ecology risk due to expose to these organic pollutants were evaluated with the multimedia environmental assessment system （MEAS）. For all the water samples, they were collected from four different locations in the drinking water sourcr samples, es of Nanjing City. The results of the comet assay showed that all the organic concentrates from the water samples could induce different levels DNA damages on human peripheral blood lymphocytes, and a statistically significant difference （p〈0.01） was observed compared with the solvent control, which demonstrated the genotoxicity was in existence. According to the ambient severity （AS） of individual compound, we had sorted out the main organic pollutants in the drinking water source of the four waterworks, and the results showed that there was some potential hazard to human body for all the source water, namely the total ambient severity （TAS） of health for each water source was more than 1. However, the TAS of ecology for each water source was less than 1, which indicated that it was safe to ecology. The results of this investigation demonstrate the application of the comet assay and the MEAS in aquatic environmental monitoring studies, and the comet assay found to be fast, sensitive, and suitable for genotoxicity monitoring programs of drinking water source.

Legislation on protection of drinking water sources and local management practices in the Pearl River Delta region of China

The protection of drinking water sources is vital to urban development and public health.In this study,the current situation of the mandatory protection area for drinking water source in the Pearl River Delta region was investigated using a method combining Google Earth with the field survey.The gaps between management practices and legislation requirements were analyzed.Finally,several countermeasures for water resource protection were proposed as follows:to promote delineation in a more scientific way,to safeguard the sanctity of the law,to make better plan on water saving,and to encourage public participation in supervision and management.

Sources and health risks of nitrate pollution in surface water in the Weihe River watershed,China

Owing to the significant reductions in streamflow and an increase in human activities in recent years,the quality of surface water in Weihe River continues to pose environmental health concerns.We utilized hydrochemistry and nitrogen and oxygen isotopes to elucidate the status and identify sources of nitrate pollution in the south and north banks for three seasons(flood,dry,and mean-flow periods)in the Weihe River watershed.A Bayesian isotope mixing model was applied to estimate the contributions of four potential NO_(3)-sources to river pollution(manure and sewage,soil nitrogen,inorganic fertilizer,and nitrate in precipitation).The U.S.Environmental Protection Agency(USEPA)evaluation model was implemented to evaluate the health risks associated with nitrate pollution in the surface water.Nitrate pollution was most severe during the dry period because the river flow was small.Due to the influence of the topography and land use type of the Weihe River,the pollution in the main stream was greater than that of the tributaries,and the pollution of the south bank was greater than that of the north bank.During the flood and mean-flow periods,δ^(15)N and δ^(18)O were mainly distributed in the NH_(4)^(+) of the fertilizer and soil nitrogen.During the dry period,δ^(15)N and δ^(18)O were mainly distributed in domestic sewage and manure regions.According to the Stable Isotope Analysis in R(SIAR)model,manure and sewage were the major nitrate sources during the dry period(73%).However,a decrease in the contribution from domestic sewage and manure was observed during the flood period(45%)compared to the dry period,but with a significantly increased contribution from soil nitrogen(23%)and inorganic fertilizer(21%).The health risk value in the dry period was higher than that in the wet and mean flow periods,and children are more susceptible to nitrate pollution than adults.Therefore,reducing the discharge of domestic sewage and manure and improving the utilization rate of nitrogen fertilizers may be effective measures to improve water quality in the watershed.

Integrated Control of Agricultural Non-point Source Pollution to Provide Safe and Healthy Drinking Water for Rural Areas

Agricultural non-point source pollution has become the main part of water pollution prevention and control in China. This paper made a brief introduction to the causes and hazards of agricultural non-point source pollution and the current situation of agricultural non-point source pollution prevention and control in China. In view of the serious agricultural non-point source pollution in water environment of Guangxi and the difference in quality of drinking water between urban and rural areas,it came up with recommendations for strengthening agricultural non-point source pollution prevention and control from scientific distribution,linked operation and maintenance,popular science education,and legal system construction,to guarantee safe and healthy drinking water in rural areas.

Genotoxicity evaluation of drinking water sources in human peripheral blood lymphocytes using the comet assay

The potential harm of organic pollutants in drinking water to human health is widely focused on in the wodd; more and more pollutants with genotoxic substances are released into the aquatic environment. Water source samples were collected from 7 different localities of Nanjing City. The potential genotoxicity of organic extracts from drinking water sources were investigated by means of the comet assay in human peripheral lymphocytes. The results showed that all the organic extracts from all the water source samples could induce DNA damages of human peripheral blood lymphocytes at different levels. A significant difference （P 〈 0.01） was observed when compared with the solvent control, The DNA damage increased with the increase of the dosage of the original water source. Significant differences of DNA damage were observed in different drinking water sources, as shown by the multiple comparisons analysis at the dosage of 100x; the degree of DNA damage treated by Hushu waterworks （at town level） was the most serious, the arbitrary units （AU） was 141.62±6.96, however, that of Shangyuanmen waterworks （at city level） was only 109.64±2.97. The analysis also revealed that the genotoxicity of town＇s water sources was higher than that of the city. The results demonstrated that the comet assay can be successfully applied to the genotoxicity monitoring programs of drinking water sources.

Distribution and characterizing sources of polycyclic aromatic hydrocarbons of surface water from Jialing River

Sixteen priority polycyclic aromatic hydrocarbons(PAHs) in surface water samples were analyzed by gas chromatograph-mass spectrometer(GC-MS) to study their distribution and characterizing sources.The water samples were collected from five sites(J1-J5) in the Jialing River of Chongqing downtown area from September 2009 to August 2010.The results demonstrate that the concentration of total PAHs in three samples upstream are relatively higher than those in other two sites downstream,with average concentration of total PAHs for each site ranging from 811.5 ng/L to 1585.8 ng/L.The 2,3 and 4-ring PAHs for sampling stations account for 13.0%,56.6% and 28.6%,respectively,in total PAHs.There are obvious tendencies of seasonal change for PAHs concentration in surface water.The PAHs concentration in April of wet season is 1 301.6 ng/L,which is 1.3 times the lowest amount of total PAHs in August of flood season.Ratios of specific PAH compounds were used to characterize the possible pollution sources.Experimental results indicate that the PAHs in surface water samples are primarily from pyrolytic PAHs because of factories along these sites,while the direct leakage of petroleum products may be significant for two sites,Jiahua Bridge(J4) and Huanghuayuan Bridge(J5),because of the wharf boat nearby.

Physico-Chemical Quality of Selected Drinking Water Sources in Mbarara Municipality, Uganda

The study assessed the physico-chemical quality of selected drinking water sources (springs, boreholes, shallow wells and rainfall) in Mbarara municipality with respect to World Health Organization (WHO) drinking water guidelines and other guidelines in light of the increased anthropogenic activities in the municipality. A total of 70 water samples were collected from purposively selected boreholes, springs, wells and rainwater in Nyamitanga, Kamukuzi and Kakoba divisions of Mbarara municipality with various human activities. The samples were analysed for physico-chemical parameters: Temperature, pH, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Total Dissolved Solids (TDS), Electrical Conductivity (EC) and Total hardness using American Public Health Association (APHA) standard methods. The mean temperature and pH ranged between 18.07 °C - 23.45 °C and 5.74 - 7.54, respectively. The mean DO values were found to be between 4.84 and 12.86 mg/l;whereas mean BOD was within the range of 1.83 - 7.71 mg/l. The mean TDS and EC of the water samples ranged, between 33.40 - 569.20 mg/l and 29.30 - 1139.90 μS/cm respectively. Furthermore, the lowest and highest mean total hardness were 70.00 and 264.00 mg/l, respectively. The recorded mean water temperatures for each of the water sources were above the WHO threshold temperature (15 °C) which makes drinking water palatable. Boreholes in Nyamitanga and Shuhaddea Secondary Schools, spring in Kiswahili, well in Kisenyi and rainwater in Mbarara University of Science and Technology (MUST) had mean pH below the WHO minimum guideline value (6.5) hence acidic. Borehole in Nyamitanga secondary school, spring in Kisenyi, shallow well in Nyamitanga and the rainwater in MUST had mean DO values below the WHO range (10 - 12 mg/l). Borehole in Shuhaddea Secondary School and the well in Kisenyi had average BOD values above the range of European Union guideline values (3 - 6 mg/l). TDS and EC of all the water sources were below the WHO maximum guideline limits of 1000 mg/l and 1500 μs/cm respectively. Total hardness was also below the WHO harmless limit of 1000 mg/l. However rainwater in MUST was moderately soft while the other drinking water sources exhibited moderate to full total hardness. The physicochemical parameters of some of the selected water sources in Mbarara municipality have been compromised mainly by the increased human activities especially croplands, latrines, landfills, transportation, animal and municipal wastes at the vicinity of the water sources. Mbarara municipal council should therefore ensure proper sanitation and water safety plans for these drinking water sources to avoid further contamination from the human activities.

Bearing splitting and near-surface source ranging in the direct zone of deep water

Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.

Inactivation Mechanisms of Escherichia Coli in Drinking Water Using Reactive Species Generated from a Surface Discharge

Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface discharge reactor(SDR)is designed:a spiral stainless steel wire attached on the inside wall of a quartz glass tube is used as the high voltage electrode,and the drinking water is the ground electrode.The performance and mechanisms of the method in inactivating of Escherichia coli(E.coli)are analyzed.Experimental results show that 500 mL E.coli-contaminated drinking water(108CFU/mL)is completely sterilized within 4 min.Based on the scanning electron microscope(SEM)analysis,there were plasma-induced cell structure damages of the E.coli in the sterilized water,and the damage resulted in the leakage of protein,which was proved by chemical analyses.Meanwhile,the heating effect concomitantly generated by discharge plasma does not influence E.coli inactivation,and the contribution of direct ultraviolet(UV)irradiation could be neglected too.The ozone generated by SDR and the hydroxyl radicals(·OH)subsequently generated in drinking water play the decisive roles in E.coli inactivation because these reactive species cause the cell rupture.

Bacterial Analysis of Selected Drinking Water Sources in Mbarara Municipality, Uganda

Surveillance of water quality to ensure microbiological safety is a vital public health function to prevent water borne diseases. Bacterial total coliform and Escherichia coli (E. coli) examination provide indication of the hygienic condition of drinking water and are major tools in the assessment of the health risk borne by pathogen in water. Unfortunately, there is insufficient information on the total coliform and E. coli amounts in the common drinking water sources in Mbarara Municipality, Uganda despite the eminent anthropogenic sources of contamination. Hence the study established the sanitary risk and quantified the total coliform and E. coli load in selected drinking water sources in Mbarara Municipality, Uganda. A total of 70 water samples were collected from selected boreholes, springs, wells and rainwater in Nyamitanga, Kamukuzi and Kakoba divisions of Mbarara municipality. The water samples were analysed for total coliform and E. coli abundance using the American Public Health Association (APHA) standard method. The total coliform and Escherichia coli counts were compared with the World Health Organization (WHO) drinking water standard guidelines. The findings indicate that all the studied groundwater sources (boreholes, springs and wells) in Mbarara Municipality were not compliant to either both or one of the WHO total coliform ( ml) and E. coli (0 CFU/100 ml) criteria for drinking water hence they are unsuitable for drinking without treatment e.g. boiling etc. Only rainwater collected from Mbarara University of Science and Technology met the WHO total coliform and E. coli criteria for drinking water thus is suitable for drinking without any treatment. There is a strong linkage between bacterial (total coliforms and E. coli) water quality and water source sanitation, as well as the proximity of latrines, animal farms and landfills around the water sources. Mbarara municipal council should therefore ensure effective and regular operation and maintenance of the drinking water sources through the adoption and promotion of appropriate water safety plans.

Study on the Characteristics of Pollutants in Surface Water Source Based on Risk Assessment

Supervision of urban water source area and the safety of drinking water is one of the important tasks in China's current environmental protection work. By reviewing screening methods of characteristic pollutants in urban water source area,screening system of pollutants based on the framework of environmental risk is introduced in detail: establish database of pollutants→determine the evaluation purpose→determine testing end and screening standard→assignment calculation→prioritization. At the same time,the application of health risk assessment and technology in the risk assessment of urban water source area is introduced,so as to provide technical support and theoretical basis for management and protection of urban water source area.

Health Risk Assessment of Centralized Drinking Water Sources in Small Towns of Chongqi City: A Case Study of Beibei District

Based on the health risk assessment model of water quality recommended by United States Environmental Protection Agency (USEPA), the health risk of five centralized drinking water sources in small towns of Beibei District, Chongqing City was evaluated. The results showed that the risk of health hazard of chemical carcinogen arsenic did not exceed the acceptable level recommended by the International Commission on Radiological Protection (ICRP)(5.0×10 -5 a -1 ), but was still at the same order of magnitude as the recommended value of ICRP. The risk of the highest health hazard was 127 times higher than the maximum acceptable level recommended by Sweden EPA and Holland EPA (1.0×10 -6 a -1 ). The health risk of As in genetic toxic substances at monitoring points A, B, and C accounted for 99.99% of the total risk, showing that As was the main pollutant that posed the health risk, so priority should be given to the prevention and control of As pollution in the centralized drinking water sources in Chongqing towns.

Suitability of Drinking Water Sources from Nyaruzinga Wetland for Domestic Use in Bushenyi Municipality, Uganda

This study determined the physico-chemical and bacterial quality of raw (bore-hole, springs, wells) and tap water sources from Nyaruzinga wetland for domestic use in Bushenyi Municipality. Forty samples of raw water were randomly collected from Kacuncu, Kyeitembe and Kikuba tributaries of the wetland and 40 samples of tap water generated from the same wetland were randomly drawn from Ishaka, Nyakabirizi and Central divisions of the Municipality. The samples were analyzed for apparent colour (AC), turbidity, electrical conductivity (EC), total hardness, pH, total iron, residual alum, free residual chlorine and faecal coliforms using standard methods and their values compared with standard local UNBS (2008) and international WHO (2011) drinking water quality guidelines. The results showed that the mean pH of the protected spring below Kikuba Hill (5.21);the AC (Pt/Co) of the borehole below Bweranyangi Junior School (17.28) and the surface well below Nyandozo Primary School (157.58) both situated in Kacuncu as well as the free residual chlorine (mg/L) in tap water at Kanyamabona Trading Centre, Ishaka division (0.192) were below the standard values of WHO (pH, 6.0 - 8.0;free residual chlorine, 0.2 - 0.5) and UNBS (AC, <15). The electrical conductivity, EC (μS/cm) and total hardness (mg/L) of all the selected water sources were within the WHO standards (EC, <1500 (raw water), 0 - 300 (tap water);total hardness, <1500 (raw water), <100 (tap water)). The residual alum (mg/L) in all the tap water sources was also within the WHO guideline (<0.2). On the other hand, the turbidity (27.38 NTUs) and total iron content (0.32 mg/L) of the surface well below Nyandozo Primary School were above WHO guidelines of <15 and <0.3 respectively. Furthermore, the mean faecal coliform counts (CFU/100 ml) in the surface well below Nyandozo Primary School (6.90) and the borehole below Bweranyangi Junior School (16.83) including the surface well below Kyeitembe Trading Centre (9.25) were above the WHO standard faecal coliform count (≤3 TCUs). Only the tap water at Kanyamabona Trading Centre recorded mean faecal coliform counts (0.25 TCUs) beyond the WHO standard (0 TCU). Hence the quality of tap water within the municipality tapped from Nyaruzinga wetland was generally better than the raw drinking water sources (borehole, springs, wells) from the same wetland. Thus the use of piped tap water by the urban inhabitants as opposed to raw water sources needs to be promoted to increase access to safe water.

Double-endpoint Genotoxicity Quantification and PAHs Characterization of Drinking Water Source alongside Polluted Yinghe River with High Tumor Mortality

The etiology for the high tumor mortality in heavy polluted Yinghe river basin is still unclear and polycyclic aromatic hydrocarbons(PAHs)belong to the priority pollutants in water based on the former surveillance data.In order to explore the potential genotoxicants contributing to the double-endpoint genotoxicity of polluted drinking water source,12 groundwater and 3 surface water samples were collected from 3 villages and the nearby rivers alongside Yinghe river basin,respectively and their comprehensive genotoxicity was estimated with a bioassay group of sOS/umu test and micronucleus(MN)test(MNT).Some groundwater samples showed positive genotoxicity and all surface water samples were highly genotoxic.Eight groundwater samples showed DNA genotoxic effct with the average 4-NQO equivalent concentration(TEQ_(4-NQO))of 0.067μg/L and 0.089μg/L in wet and dry season,respectively.The average MN ratios of groundwater samples were 14.19‰ and 17.52‰ in wet and dry season,respectively.Groundwater samples showed different genotoxic effect among 3 villages.The total PAHs concentrations in all water samples ranged from 8.98 to 25.17 ng/L with an average of 14.97±4.85 ng/L.BaA,CHR,BkF,BaP and DBA were the main carcinogenic PAHs contributing to the genotoxicity of water samples.In conclusion,carcinogenic PAHs are possibly related to the high tumor mortality in the target area.Characterization of carcinogenic PAHs to genotoxicity of drinking water source may shed light on the etiology study for high tumor mortality in Yinghe river basin.Key words:genotoxicity test;drinking water source;high tumor mortality;Yinghe river basin;polycyclic aromatic hydrocarbons(PAHs)

Form Distribution Characteristics of Nitrogen in a Reservoir as Drinking Water Source

Based on field detected water quality data, the distribution characteristics of different forms of nitrogen in a reservoir as drinking water source in Dongguan, which locates at the Pearl River Delta of China, have been analyzed in order to provide theoretical bases for prevention and reduction of eutrophication. The analyzed results show that nitrogen forms in the influent area of the reservoir are given priority to ammonia nitrogen and nitrate nitrogen, whose proportion is more than 45% respectively, and this is probably caused by the pollution of inflow water quality;but in the effluent area, the forms are given priority to nitrate nitrogen, whose proportion is as high as 96% and above;also the proportion of ammonia nitrogen drops by more than 80% during the process from the influent area to the effluent area, and this shows that the natural process of nitrification and denitrification can be well accomplished in the reservoir. We recommend here that to reduce the input amount of ammonia nitrogen and organic nitrogen into the reservoir is the most efficient way to prevent or mitigate eutrophication of water body.

Riparian habitat quality as an indicator of land use/land cover effects on riverine water quality

Riparian land use/land cover(LULC)plays a crucial role in maintaining riverine water quality by altering the transport of pollutants and nutrients.Nevertheless,establishing a direct relationship between water quality and LULC is challenging due to the multi-indicator nature of both factors.Water quality encompasses a multitude of physical,chemical,and biological parameters,while LULC represents a diverse array of land use types.Riparian habitat quality(RHQ)serves as an indicator of LULC.Yet,it remains to be seen whether RHQ can act as a proxy of LULC for assessing the impact of LULC on riverine water quality.This study examines the interplay between RHQ,LULC and water quality,and develops a comprehensive indicator to predict water quality.We measured several water quality parameters,including pH(potential of hydrogen),TN(total nitrogen),TP(total phosphorus),T_(water)(water temperature),DO(dissolved oxygen),and EC(electrical conductivity)of the Yue and Jinshui Rivers draining to the Han River during 2016,2017 and 2018.The water quality index(WQI)was further calculated.RHQ is assessed by the InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model.Our study found noticeable seasonal differences in water quality,with a higher WQI observed in the dry season.The RHQ was strongly correlated with LULC compositions.RHQ positively correlated with WQI,and DO concentration and vegetation land were negatively correlated with T_(water),TN,TP,EC,cropland,and construction land.These correlations were stronger in the rainy season.Human-dominated land,such as construction land and cropland,significantly contributed to water quality degradation,whereas vegetation promoted water quality.Regression models showed that the RHQ explained variations in WQI better than LULC types.Our study concludes that RHQ is a new and comprehensive indicator for predicting the dynamics of riverine water quality.

Drinking water production by uitrafiltration of Songhuajiang River with PAC adsorption

In recent years, membrane ultrafiltration （UF） of surface water for drinking water treatment has become a more attractive technology worldwide as a possible alternative treatment to conventional clarification. To evaluate the performance of ultrafiltration membranes for treatment of surface water in North China, a 48-m^2 low pressure hollow fiber membrane ultrafiltration pilot plant was constructed. Ultrafiltration was operated in cross-flow and with powdered activated carbon （PAC） adsorption. Turbidity was almost completely removed to less than 0.2 NTU （below Chinese standard 1 NTU）. It was found that PAC addition enhanced organic matter removal. The combined process of PAC/UF allowed to 41% removal of CODMn, 46% removal of DOC and 57% decrease in UV254 absorbance. The elimination of particles, from average 12000/ml in the raw water to approximately 15/ml in the permeated, was observed. When PAC concentration was below 30 mg/L, backwashing could recovery the membrane flux with backwash interval/backwashing duration of 1/30.