A review of physicochemical and biological contaminants in drinking water and their impacts on human health

Clean drinking water is one of the United Nations Sustainable Development Goals.Despite significant progress in the water purification technology,many regions still lack access to clean water.This paper provides a review of selected water contaminants and their impacts on human health.The World Health Organization(WHO)guidelines and regional standards for key contaminants were used to characterise water quality in the European Union and UK.The concept of safe drinking water was explained based on the non-observed adverse effect level,threshold concentrations for toxic chemicals,and their total daily intake.Various techniques for monitoring water contaminants and the drinking water standards from five different countries,including the UK,USA,Canada,Pakistan and India,were compared to WHO recommended guidelines.The literature on actual water quality in these regions and its potential health impacts was also discussed.Finally,the role of public water suppliers in identifying and monitoring drinking water contaminants in selected developed countries was presented as a potential guideline for developing countries.This review emphasised the need for a comprehensive understanding of water quality and its impacts on human health to ensure access to clean drinking water worldwide.

Surface flow constructed wetland with composite plant bed for pretreatment of micro-polluted Yellow River raw water in China

In order to investigate the feasibility of pretreating the micro-polluted Yellow River raw water by constructed wetland, an experiment was conducted using a surface flow constructed wetland with composite plant bed. The contamination removal efficiency and their trends in the wetland treatment system were studied under different hydraulic loading rates(HLR). The contamination removal efficiencies were compared according to the seasonal change under optimum HLR. The result shows that in the same season, under different hydraulic loadings ranging from 2 to 6 m3/(m2·d) at the same period, the best HLR is 4 m3/(m2·d) in the experimental system. The average removal rates of COD, TN, ammoniacal nitrogen(NH4+-N), and TP in the constructed wetland are 38.37%, 45.97%, 39.86% and 41.69%, respectively. According to China Standard for Surface Water Resources (GB3838-2002), mean effluent of COD, TN, NH4+-N and TP can nearly reach Grade Ⅲ, GradeⅤ, GradeⅠand GradeⅠ, respectively. Furthermore, treatment efficiency of the system in summer is obvious higher than that in other seasons. The expenditure of constructing the constructed wetland with the average treating capacity of 176 m3/d and lifetime of 20 years is 17075.00 RMB. The average disposal cost is summed up to 0.17 RMB/m3, which shows that the pretreatment of the micro-polluted Yellow River raw water by constructed wetland is feasible.

Application of Green Technology Using Biological Means for the Adsorption of Micro-Pollutants in Water

It is true that the world we have today is not the world we use to know. The Covid-19 pandemic has paralyzed all sector, hence the need for safety and enabling environment for mankind is of high importance. Adsorption technology is far the best and cheapest treatment technology for water and has extensively proven its worth for the uptake of micro-pollutant from surface, ground and water which are the major channels of home water. Over the years activated carbon is considered as the most common and universally used adsorbent for the eradication of different types of micro-pollutants from water. The contamination of surface water by micro-pollutant is a potential threat for the production of high quality and safe drinking water. Adsorption operation onto granulated activated carbon (GAC) in fixed-bed filters is often applied as a remedying step in the synthesis of safe and drinkable water. Activated carbon actively tends to act as a carrier material for a thin usually resistant layer of microorganisms (mostly bacteria) that forms on the coat of various surfaces (biofilm), hence biological simplification can be an alternative removal approach that can be adopted in granulated activated carbon filters. To evaluate the capacity of biofilm to biologically simplify micro-pollutants, it is very imperative to distinguish adsorption from biological simplification (biodegradation) as a removal mechanism. Experiment was carried out under the operating condition of a temperature range of 6?C to 20?C with biologically activated and autoclaved GAC to assess the biological simplification by the biofilm adsorbed on the GAC surface. Five micro-pollutants were selected as model compounds, of which some of them were biologically simplified by the GAC biofilm. Additionally, we observed that temperature can increase or decrease adsorption. Conclusively, comparison was made on the adsorption capacity of granulated activated carbon used for more than 50,000 beds.

Phosphorus limitation in biofiltration for drinking water treatment

Bacterial growth potential(BGP) method and two parallel pilot scale biofilters were used to investigate phosphorus limitation and its effect on the removal of organic matters in biofiltration for drinking water treatment. Addition of phosphorus can substantially increase the BGPs of the samples. Its effect was equivalent to that of addition of a mixture of various inorganic nutrients including phosphorus. The biofilter with phosphate added into its influent performed a higher biological stability of the effluent and a higher COD Mn removal than the control filter. These results suggested that phosphorus was the limiting nutrient in the biofiltration and the removal efficiency of organic matters could be improved by adding phosphate into the influent.

Phosphorus limitation on bacterial regrowth in drinking water

Assimilable organic carbon(AOC) test and bacterial regrowth potential(BRP) analysis were used to investigate the effect of phosphorus on bacterial regrowth in the drinking water that was made from some raw water taken from a reservoir located in northern China. It was shown that AOC of the drinking water samples increased by 43.9%—59.6% and BRP increased by 100%—235% when 50 μg/L PO 3- 4-P(as NaH 2PO 4) was added alone to the drinking water samples. This result was clear evidence of phosphorus limitation on bacteria regrowth in the drinking water. This investigation indicated the importance of phosphorus in ensuring biological stability of drinking water and offered a novel possible option to restrict microbial regrowth in drinking water distribution system by applying appropriate technologies to remove phosphorus efficiently from drinking water in China.

Performance of BAC process for treatment of micro-polluted water

Biological activated carbon (BAC) has been developed on the granular activated carbon by immobilization of selected and acclimated species of bacteria to treat the micro-polluted water. The BAC removal efficiencies for nitrobenzene, permanganate index, turbidity and ammonia were investigated. Effects of shock loading and SEM (Scanning Electron Microscope) observation on BAC were studied. Backwashing and its intensity of BAC were also discussed. The results showed that BAC took short time to start up and recover to the normal condition after shock loading. The shock loading studies showed that the removal efficiency of BAC was not completely inhibited even at high concentration of nitrobenzene. Backwashing performed once every 10-20 d, or an average of 15 d. Backwashing intensity was 12-14 L/(s·m2) with air and 3-4 L/(s·m2) with water.

Improving Removal Efficiency of Organic Matters by Adding Phosphorus in Drinking Water Biofiltration Treatment

Objective To investigate phosphorus limitation and its effect on the removal efficiency of organic matters in drinking water biological treatment. Methods Bacterial growth potential (BGP) method and a pair of parallel pilot-scale biofilters were used for the two objectives, respectively. Results The addition of phosphorus could substantially increase the BGPs of the water samples and the effect was stronger than that of the addition of carbon. When nothing was added into the influents, both CODMn removals of the parallel biofilters (BF1 and BF2) were about 15%. When phosphate was added into its influent, BF1 performed a CODMn removal, 6.02 percentage points higher than the control filter (BF2) and its effluent had a higher biological stability. When the addition dose was <20μg. L-1, no phosphorus pollution would occur and there was a good linear relationship between the microbial utilization of phosphorus and the removal efficiency of organic matters. Conclusions Phosphorus was a limiting nutrient and its limitation was stronger than that of carbon. The addition of phosphate was a practical way to improve the removal efficiency of organic matters in drinking water biological treatment.

Novel FGBAC reactor for controlling the leakage of microfauna in drinking water treatment

In order to reduce the microfauna leakage risk from a granular biological activated carbon （GBAC） reactor which employs granular activated carbon （GAC） as adsorption media in drinking water advanced treatment, a novel fiber and granular biological activated carbon （FGBAC） reactor which employs both GAC and activated carbon fiber （ACF） as adsorption media, was developed. The results showed that the species composition of microfauna leaking from FGBAC reactor is almost similar to that leaking from GBAC reactor, however the densities of microfauna leaking from FGBAC reactor is reduced by 26%-81% compared to those leaking from GBAC reactor. In addition, compared to GBAC reactor, FGBAC reactor can increase the removal efflciencies of chemical oxygen demand （COD） and turbidity by 7% and 10%, respectively, during the stable operation period of reactor.

Water-lifting and aeration system improves water quality of drinking water reservoirs: Biological mechanism and field application

Reservoirs have been served as the major source of drinking water for dozens of years.The water quality safety of large andmedium reservoirs increasingly becomes the focus of public concern.Field test has proved that water-lifting and aeration system(WLAS)is a piece of effective equipment for in situ control and improvement of water quality.However,its intrinsic bioremediation mechanism,especially for nitrogen removal,still lacks in-depth investigation.Hence,the dynamic changes inwater quality parameters,carbon source metabolism,species compositions and co-occurrence patterns ofmicrobial communitieswere systematically studied in Jinpen Reservoir within a wholeWLAS running cycle.TheWLAS operation could efficiently reduce organic carbon(19.77%),nitrogen(21.55%)and phosphorus(65.60%),respectively.Biolog analysis revealed that the microbialmetabolic capacitieswere enhanced viaWLAS operation,especially in bottomwater.High-throughput sequencing demonstrated that WLAS operation altered the diversity and distributions of microbial communities in the source water.The most dominant genus accountable for aerobic denitrification was identified as Dechloromonas.Furthermore,network analysis revealed that microorganisms interacted more closely through WLAS operation.Oxidation-reduction potential(ORP)and total nitrogen(TN)were regarded as the two main physicochemical parameters influencing microbial community structures,as confirmed by redundancy analysis(RDA)and Mantel test.Overall,the results will provide a scientific basis and an effective way for strengthening the in-situ bioremediation of micro-polluted source water.

17α-Ethinylestradiol removal from water by magnetic ion exchange resin

Magnetic ion exchange(MIEX) resins have received considerable attention in drinking water treatment due to their fast and efficient removal of dissolved organic carbon(DOC). Two types of mechanisms, i.e., ion exchange,reversible and irreversible adsorption, may occur during pollutants removal by MIEX. This work examined the removal mechanism of 17α-Ethinylestradiol(EE2) by MIEX. As one of typical estrogen micro-pollutants,EE2 existed as neutral molecule in natural water, and its charge density was close to zero [(0.00000219 ±0.00000015) meq·(μg EE2)^(-1)] based on the potentiometric titration method. However, the removal of EE2 by MIEX was much higher than that of other micro-pollutants previously reported. Multi-cycle adsorptionregeneration experiments and ion exchange stoichiometry analysis were conducted to elucidate the removal mechanism of EE2 by MIEX resin. The results suggested that the main removal mechanism of EE2 by MIEX was ion exchange instead of reversible micro-pore adsorption. The experimental analysis based on Donnan theory indicated that the internal micro-environment of resin beads was alkaline, in the alkaline environment EE2 would be ionized into negatively charged groups. As a result, ion exchange reaction occurred inside the pore of MIEX resin, and the removal process of EE2 by MIEX was dominated by the ion exchange reaction.

Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment

Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems（DWDSs） composed of annular reactors incorporating three different treatments： ozone, biologically activated carbon and chlorination（O3-BAC-Cl2）;ozone and chlorination（O3-Cl2）; or chlorination alone（Cl2）. The lowest corrosion rate and iron release, along with more Fe3O4 formation, occurred in DWDSs with O3-BAC-Cl2 compared to those without a BAC filter. It was verified that O3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria（NRB）in DWDSs. Moreover, the advantaged NRB induced active Fe（III） reduction coupled to Fe（II） oxidation, enhancing Fe3O4 formation and inhibiting corrosion. In addition, O3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.

Screening for 26 per-and polyfluoroalkyl substances(PFAS)in German drinking waters with support of residents

The occurrence of per-and polyfluoroalkyl substances(PFAS)in water cycles poses a challenge to drinking water quality and safety.In order to counteract the large knowledge gap regarding PFAS in German drinking water,89 drinking water samples from all over Germany were collected with the help of residents and were analyzed for 26 PFAS by high-performance liquid chromatography with tandem mass spectrometry(HPLC-MS/MS).The 20 PFAS recently regulated by sum concentration(PFAS_(∑20)),as well as six other PFAS,were quantified by targeted analysis.In all drinking water samples,PFAS_(∑20 )was below the limit of 0.1μg/L,but the sum concentrations ranged widely from below the limit of quantification up to 80.2 ng/L.The sum concentrations(PFASP4)of perfluorohexanesulfonate(PFHxS),perfluorooctanesulfonate(PFOS),perfluorooctanoate(PFOA),and perfluorononanoate of 20 ng/L were exceeded in two samples.The most frequently detected individual substances were PFOS(in 52%of the samples),perfluorobutanesulfonate(52%),perfluorohexanoate(PFHxA)(44%),perfluoropentanoate(43%)and PFHxS(35%).The highest single concentrations were 23.5 ng/L for PFHxS,15.3 ng/L for PFOS,and 10.1 ng/L for PFHxA.No regionally elevated concentrations were identified,but some highly urbanized areas showed elevated levels.Concentrations of substitution PFAS,including 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate and 2,2,3-trifluor-3-[1,1,2,2,3,3-hexafluor-3-(trifluormethoxy)propoxy]-propanoate(anion of ADONA),were very low compared to regulated PFAS.The most frequently detected PFAS were examined for co-occurrences,but no definite correlations could be found.

某市供水系统饮用水中有机物的毒性及其影响因素

为了解某市饮用水中有机物的生物毒性及其影响因素,在2018年6月至2019年9月期间采集该市A、B两个水厂的水源水、出厂水和管网水,测定水样有机提取物对费式弧菌(Vibrio fischeri)发光的抑制作用,计算引起50%发光抑制的浓度(EC_(50)),并分析其与水样在254 nm波长处的紫外吸光度值(UV_(254))、溶解性有机碳(DOC)浓度的关联。结果表明:饮用水有机提取物EC_(50)值范围为0.23~98.97 REF(相对富集系数),中位数为3.37 REF。水文期、常规饮用水处理工艺、管网输送过程及水源水UV_(254)和DOC浓度水平对饮用水中有机物的毒性无明显影响。饮用水UV_(254)、DOC浓度与有机提取物EC_(50)的Spearman相关系数分别为-0.025(P=0.807)、-0.237(P=0.020),表明不能用UV_(254)、DOC浓度检测代替毒性测试来监测饮用水有机物污染的潜在健康风险。

饮用水厂含藻原水加压处理的实验研究

饮用水厂的原水多取自湖泊和水库等封闭水体,较高浓度的含藻原水影响居民用水质量,现有除藻技术对含藻原水处理效果差,或使藻细胞破裂、释放胞内物质,造成二次污染。本研究采用加压处理含藻水,消除藻类对饮用水质的影响。通过小试实验研究了加压预处理的除藻效果和参数。结果表明,加压处理对典型微囊藻类——铜绿微囊藻有较为明显的去除效果,当压强增大到0.7 MPa时效果最佳,可达到最大除藻效果。加压使囊泡破裂是一个瞬间且不可逆的过程,加压不会使藻细胞破裂,其内容物未释放而污染水体。

高级氧化工艺对饮用水控藻除嗅的研究进展

当前各水源地水华暴发现象频发,导致水源水质污染严重。土臭素(GSM)和2-甲基异莰醇(2-MIB)是较为常见的藻类代谢嗅味产物,也是导致水体产生土臭味的主要原因。常规除藻技术虽然能够去除水体中的藻类,但对其生成的嗅味产物去除效果不佳,因此,亟需新技术在除藻的情况下实现同步去除嗅味产物。文中结合藻类与嗅味产物的相关性,综述常规除藻技术的局限性,介绍高级氧化工艺(AOPs)对于两者去除的研究应用,并认为AOPs将成为同步除藻除嗅技术的研究热点,为同时除藻除嗅技术进一步研究与应用提供理论依据。

净水厂生物活性炭微生物解析和风险研究进展

系统梳理了活性炭表面存在的微生物类群和优势物种,其中原核生物中变形菌门和拟杆菌门常为其中的优势菌门,真核生物以原生动物和微型后生动物为主;并对某些优势菌群在污染物去除过程中的潜在功能进行了总结,大多数为好氧的化能有机异养微生物。还探讨了可能存在的风险微生物,水源性耐氯细菌病原体属于放线菌亚纲、芽孢杆菌纲和γ-变形菌纲;并归纳了影响微生物群落的因素,包括载体、水质条件、剩余臭氧和进水流向。研究结果有望为净水厂臭氧/生物活性炭工艺的精确调控提供理论依据和技术支撑。

废生物活性炭制备粉末炭的热再生效能

为实现水厂废生物活性炭资源化利用,本文将废生物活性炭研磨成粉末炭,探讨热再生温度对粉末炭理化性质的影响,观测再生粉末炭对水中典型有机污染物的去除效能。结果表明:粉末炭的热解经历了水分子脱附(35~105℃)、易挥发有机物脱附(105~400℃)和沸点较高有机物热解(400~735℃)3个过程;热再生能够显著恢复粉末炭的孔隙结构,碘值、亚甲基蓝值的恢复率分别达到83.1%、75.9%,并且恢复率随着再生温度升高逐渐升高;热再生会导致粉末炭的酸性官能团含量减少,碱性官能团含量增加,而表面氧元素含量随着再生温度升高先增加后降低;热再生降低了粉末炭水溶性有机物浸出;通过热再生能够显著提升粉末炭对原水中典型有机污染物的控制效果,有机污染物去除率提高了7.7%~35.9%。

给水厂嗅味及溴化物复合微污染原水处理试验与工程应用

随着农村城市化、农业工业化的推进,水环境受到了污染。针对水的浑浊度、菌类仅采用混凝、沉淀、过滤、消毒工艺的水厂不能大幅度降低水中溶解杂质,不可避免地引起了自来水水质变化。以山东省新泰市Q水厂为例,自2010年开始,水库水源水因网箱养鱼和支流河道污水汇入,导致藻类繁殖,高锰酸盐指数(COD_(Mn))、氨氮等污染物含量增加,水质恶化。藻类破裂释放的微囊藻毒素和放线菌代谢产生的土臭素(geosmin,GSM)、2-甲基异莰醇(2-methylisoborneol,2-MIB)严重影响了饮用水供水水质。根据微污染杂质的主要成分、变化规律及产生的环境因素、生物因素等,特对强化常规处理法、物理吸附法、化学氧化法、生物降解等微污染水源水处理方法进行比较分析。认为采用臭氧(O_(3))氧化还原能有效氧化藻致嗅化合物和微囊藻毒素。考虑到当地水源水中含有溴化物的特点,选用O_(3)氧化和生物活性炭(BAC)过滤联用较为合理。经对Q水厂出厂水试验,在水温为10℃左右、O_(3)投加量≤2.0 mg/L、BAC滤池空床接触时间为12 min,具有去除CODMn50%、氨氮40%以上、溴酸盐≤0.01 mg/L的效果。按此工艺实施Q水厂升级改造工程,实现了出厂水水质稳定达标。通过对O_(3)-BAC工艺的处理效能持续监测和低温条件下的强化处理运行管控研究发现:低温季节,气水冲洗活性炭滤层摩擦剧烈,生物膜脱落,增殖缓慢,降低生物氧化降解作用,除污染效果变差。调整冲洗方式后,改善了这一现象;选用水并联、O_(3)化氧气串联的完全混合连续式反应器(CSTR)溶解臭氧化气体,增大气、水接触面积和气体浓度差、加快液膜紊动更新,和通用的水串联、O_(3)化气体并联的鼓泡式反应器相比,极大提高了O_(3)化气体溶解度。理论计算,制水成本减少了44.63%。

家用反渗透净水机系统匹配方法研究

随着人民生活水平的提高,对净水产品的需求逐年增加。本研究通过实验分析,探讨了反渗透技术在家用净水机中的应用,针对中国特有的水质情况,提出了一套反渗透系统的合理配置方法。通过对比测试,本研究证实了采用优化后的家用反渗透净水系统,能够高效净化自来水,出水水质满足饮用水卫生安全标准要求,证明了其在实现饮用水深度净化方面的优势。

Effects of advanced oxidation pretreatment on residual aluminum control in high humic acid water purification

Due to the formation of disinfection by-products and high concentrations of Al residue in drinking water purification, humic substances are a major component of organic matter in natural waters and have therefore received a great deal of attention in recent years. We investigated the effects of advanced oxidation pretreatment methods usually applied for removing dissolved organic matters on residual Al control. Results showed that the presence of humic acid increased residual Al concentration notably. With 15 mg/L of humic acid in raw water, the concentrations of soluble aluminum and total aluminum in the treated water were close to the quantity of Al addition. After increasing coagulant dosage from 12 to 120 mg/L, the total-Al in the treated water was controlled to below 0.2 mg/L. Purification systems with ozonation, chlorination, or potassium permanganate oxidation pretreatment units had little effects on residual Al control; while UV radiation decreased Al concentration notably. Combined with ozonation, the effects of UV radiation were enhanced. Optimal dosages were 0.5 mg O 3 /mg C and 3 hr for raw water with 15 mg/L of humic acid. Under UV light radiation, the combined forces or bonds that existed among humic acid molecules were destroyed; adsorption sites increased positively with radiation time, which promoted adsorption of humic acid onto polymeric aluminum and Al（OH） 3 （s）. This work provides a new solution for humic acid coagulation and residual Al control for raw water with humic acid purification.