Particle properties in granular activated carbon filter during drinking water treatment

The elemental composition and bacteria attached in particles were investigated during granular activated carbon （GAC） filtration.The experimental results showed that trapped influent particles could form new,larger particles on GAC surface.The sloughing of individuals off GAC surface caused an increase in effluent particles in the size range from 5 to 25 μm.The selectivity for element removal in GAC filters caused an increasing proportion of metallic elements in the effluent particles.The distribution of molar ratio indicated a complicated composition for large particles,involving organic and inorganic substances.The organic proportion accounted for 40% of total carbon attached to the particles.Compared with dissolved carbon,there was potential for the formation of trihalomethanes by organic carbon attached to particles,especially for those with size larger than 10 μm.The pure carbon energy spectrum was found only in the GAC effluent and the size distribution of carbon fines was mainly above 10 μm.The larger carbon fines provided more space for bacterial colonization and stronger protection for attached bacteria against disinfection.The residual attached bacteria after chorine disinfection was increased to 10 2-10 3 CFU/mL within 24 hours at 25°C.

Particle size distribution and property of bacteria attached to carbon fines in drinking water treatment

The quantitative change and size distribution of particles in the effluents from a sand filter and a granular activated carbon （GAC） filter in a drinking water treatment plant were investigated. The average total concentration of particles in the sand filter effluent during a filter cycle was 148 particles/mL, 27 of which were larger than 2 μm in size. The concentration in the GAC effluent （561 particles/mL） was significantly greater than that in the sand filter effluent. The concentration of particles larger than 2 μm in the GAC filter effluent reached 201 particles/mL, with the amount of particles with sizes between 2 μm and 15 μm increasing. The most probable number （MPN） of carbon fines reached 43 unit/L after six hours and fines between 0.45 μm and 8.0 μm accounted for more than 50%. The total concentration of outflowing bacteria in the GAC filter effluent, 350 CFU （colony-forming units） /mL, was greater than that in the sand filter effluent, 210 CFU/mL. The desorbed bacteria concentration reached an average of 310 CFU/mg fines. The disinfection efficiency of desorbed bacteria was lower than 40% with 1.5 mg/L of chlorine. The disinfection effect showed that the inactivation rate with 2.0 mg/L of chloramine （90%） was higher than that with chlorine （70%）. Experimental results indicated that the high particle concentration in raw water and sedimentation effluent led to high levels of outflowing particles in the sand filter effluent. The activated carbon fines in the effluent accounted for a small proportion of the total particle amount, but the existing bacteria attached to carbon fines may influence the drinking water safety. The disinfection efficiency of desorbed bacteria was lower than that of free bacteria with chlorine, and the disinfection effect on bacteria attached to carbon fines with chloramine was better than that with only chlorine.

Pilot Study on Nanofiltration Combined with Ozonation and GAC for Advanced Drinking Water Treatment

A pilot-scale study of advanced drinking water treatment was carried out in test site, and a combination of ozonation, granular activated carbon (GAC) and nanofiltration was employed as the experimental process. By optimizing the operational parameters of ozonation and GAC, a large quantity of micro-pollutants in drinking water was removed, which made the post-positioned nanofiltration operate more reliably. It was evident that nanofiltration shows good performance for removing residual organic matter, meantime partial minerals can also be retained by nanofiltration. Therefore the quality of drinking water can be further improved. In addition, NF membrane fouling and scaling can be solved by concentrate recycling, anti-scalant dosing and chemical rinsing effectively. By GAC adsorption for the residue chlorine and ozone self-decomposition, their oxidation on NF membrane material can be eliminated completely.

Combination of chlorine and magnetic ion exchange resin for drinking water treatment of algae

The effectiveness of a magnetic ion exchange resin （MIEX） for the treatment of Hongze Lake water in China was evaluated, The kinetics of natural organic matter （NOM） removal at various MIEX doses and contact time, multiple-loading experiments, impacts of MIEX prior to coagulation on coagulant demands and the effectiveness of combination of MIEX, pre-chlorination and coagulation were investigated. Kinetic experimental results show that more than 80% UV254 and 67% dissolved organic carbon （DOC） from raw water can be removed by the use of MIEX alone. 94% sulfate, 69% nitrate and 98% bromide removals are obtained after the first use of MIEX in multiple-loading experiments. It is suggested that MIEX can be loaded up to 1 250 bed volume （BV, volume ratio of tested water to resin） or more without saturation when regarding organics removal as a target. MIEX can remove organics to a greater extend than coagulation and lower the coagulant demand when combining with coagulation. Chlorination experimental results show that MIEX can remove 57% chlorine demand and 77% trihalomethane formation potential （THMFP） for raw water. Pre-chlorination followed by MIEX and coagulation can give additional organic and THMFP removals. The results suggest that MIEX provides a new method to solve thc problem algae reproduction.

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.

Immobilization biological activated carbon used in advanced drinking water treatment

Bacteria separated from a mature filter bed of groundwater treatment plants were incubated in a culture media containing iron and manganese. A consortium of 5 strains of bacteria removing iron and manganese were obtained by repeated enrichment culturing. It was shown from the experiments of effect factors that ironmanganese removal bacteria in the euhure media containing both Fe and Mn grew better than in that containing only Fe, however, they were unable to grow in the culture media containing only Mn. When comparing the bacteria biomass in the case ofp （DO） ：2.8 mg/L andp （DO） ：9. 0 mg/L, no significant difference was found. The engineering bacteria removing the organic and the bacteria removing iron and manganese were simuhaneously inoculated into activated carbon reactor to treat the effluent of distribution network. The experimental results showed that by using IBAC （ Immobilization Biological Activated Carbon） treatment, the removal efficiency of iron, manganese and permanganate index was more than 98% , 96% and 55% , respectively. After the influent with turbidity of 1.5 NTU, color of 25 degree and oflbnsive odor was treated, the turbidity and color of effluence were less than 0.5 NTU and 15 degree, respectively, and it was odorless. It is determined that the cooperation function of engineering bacteria and activated carbon achieved advanced drinking water treatment.

Effect of typhoon with extreme precipitation on mountain reservoir drinking water treatment: a case study in Ningbo, China

Due to frequent drinking water pollution accidents in the past decade, it is common that mountain reservoirs were used as the source of drinking water in China. However, some coastal areas frequently suffer from typhoon with extreme precipitation, which results in the water quality deterioration of the reservoirs. The influence of typhoons with extreme precipitation on Jiaokou reservoir and the emergency treatment process of Maojiaping water treatment plant in the past three typical typhoons with extreme precipitation from the year of 2012-2015 were studied. It was found that the degradation of water quality, such as the increase of turbidity and bacteria index, may not merely appear during the events, but last for several days. Changing the dosage of water purification agent, such as coagulant and disinfectant at right time and place may be an efficient emergency water treatment process. Based on the analysis of water quality variation rule during and after the events, it was also found that emergency treatment can be fully prepared before the arrival of a typhoon with extreme precipitation. And in order to better respond to the typhoon with extreme precipitation, several suggestions are also proposed in this paper as follows: establishing vegetated buffers at right place, such as macrophanerophytes,shrub or herbage, increasing investments in infrastructure management, merging or cancelling the small-scale water treatment plants, preparing adequate water purification agent before the typhoon comes, etc.

Sonication for advanced drinking water treatment

This paper investigated the feasibility of sonication as an advanced treatment method for drinking water production and used comprehensive indexes of water quality to examine its efficiency. Results show that sonication significantly reduces the toxicity of water. Sonication with 5 W/L at 90 kHz lasting for 30 rain decreases the water SUVA and the disinfection byproduct formation potential （DBPFP） by 38.7% and 27. 2% respectively. Sonication also decreases the UV254 by more than 50% through destroying unsaturated chemical bonds. Higher sound intensity and higher frequency benefit the reduction of TOC and UV254. Besides, sonication significantly increases the affinity of organics with granular activated carbon （ GAC ） , and thus the hybrid sonication-GAC method reduces the water TOC, COD, UV254, and DBPFP by 78.3%, 69.4%, 75.7%, and 70.0% respectively. Therefore, sonication and the hybrid sonication-GAC metbod are proposed as advanced treatment methods for drinking water.

Pilot Study on Drinking Water Advanced Treatment by GAC-MF System

The pilot performance of the combined GAC-MF membrane process for drinking water advanced treatment was described. In the process of GAC adsorption, under the conditions of 20 min HRT and 6 m/h filtration rate, the removal efficiencies of UV_(254) and trichloromethane could reach 40% and 50% respectively and the UV_(254) and trichloromethane in system effluent was less than 0.015 cm^(-1) and 5μg/L respectively. In the post MF membrane process, MF membrane effectively retained the particles and bacteria in raw water. The effluent turbidity was less than 0.2 NTU and no bacteria were detected at all in permeate. A computer-controlled system was employed to control this system. The membrane operating parameters of backwash interval, duration and flux were studied. The backwash interval of 10-min, 20-min and 60-min was researched respectively, and the variation of trans-membrane pressure was also analyzed. Consequently short backwash interval was recommended under the same water consume.

Problems of drinking water treatment along Ismailia Canal Province, Egypt

The present drinking water purification system in Egypt uses surface water as a raw water supply without a preliminary filtration process.On the other hand,chlorine gas is added as a disinfectant agent in two steps,pre-and post-chlorination.Due to these reasons most of water treatment plants suffer low filtering effectiveness and produce the trihalomethane(THM) species as a chlorination by-product.The Ismailia Canal represents the most distal downstream of the main Nile River.Thus its water contains all the proceeded pollutants discharged into the Nile.In addition,the downstream reaches of the canal act as an agricultural drain during the closing period of the High Dam gates in January and February every year.Moreover,the wide industrial zone along the upstream course of the canal enriches the canal water with high concentrations of heavy metals.The obtained results indicate that the canal gains up to 24.06×106 m3 of water from the surrounding shallow aquifer during the closing period of the High Dam gates,while during the rest of the year,the canal acts as an influent stream losing about 99.6×106 m3 of its water budget.The reduction of total organic carbon(TOC) and suspended particulate matters(SPMs) should be one of the central goals of any treatment plan to avoid the disinfectants by-products.The combination of sedimentation basins,gravel pre-filtration and slow sand filtration,and underground passage with microbiological oxidation-reduction and adsorption criteria showed good removal of parasites and bacteria and complete elimination of TOC,SPM and heavy metals.Moreover,it reduces the use of disinfectants chemicals and lowers the treatment costs.However,this purification system under the arid climate prevailing in Egypt should be tested and modified prior to application.

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.

Efficiency characterization of ceramic filtering materials used for drinking water treatment

For ceramic filtering materials, their adsorption capacities, purification efficiencies to remove organic compounds from drinking water, and correlation between adsorption capacities and pore structures were tested and analyzed. The results show that correlation coefficient between the specific surface area and the adsorptive amount of iodine molecule is 0.99; correlation coefficient between the pore volume and the adsorptive value of tannin molecule is 0.92, and correlation coefficient between the most probable diameter and the adsorption parameter is 1.0. A new method of morphology characterization for ceramic filtering materials was developed, which offered a sort of standard for the evaluation on water purification efficiencies and selection of ceramic filtering materials.

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.

Collaborative Efforts and Strategies for Cholera Outbreak Control in Garissa County, Kenya: Implementation of Water Quality Monitoring Interventions

A multi-faceted Case Area Targeted Intervention (CATI) approach emphasizing the integration of Water, Sanitation and Hygiene (WASH) interventions and Oral Cholera Vaccine (OCV) campaign was employed to respond to the outbreak of cholera in Garissa County. Drinking water sources in areas heavily impacted by cholera were systematically mapped and tested for microbiological quality. The quality assessment was carried out in April 2023 during an ongoing cholera outbreak in the county. A total of 109 samples were collected and tested for thermotolerant coliforms and other in situ parameters. The finding revealed that more than 87% of the samples did not meet the World Health Organization (WHO) standard for thermotolerant coliforms;and 30% had turbidity values above the recommended threshold values. None of the 109 samples had any traceable residual chlorine. Following these findings, the county government implemented the targeted interventions which resulted in a positive impact in the fight against cholera. The WHO supported key interventions which included capacity building in water quality monitoring and prepositioning of critical WASH commodities to the cholera affected areas.

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.

Production of Natural Coagulant from Moringa Oleifera Seed for Application in Treatment of Low Turbidity Water

This study focused on developing an efficient and cost effective processing technique for Moringa oleifera seeds to produce natural coagulant for use in drinking water treatment. The produced natural coagulant can be used as an alternative to aluminum sulphate and other coagulants and used worldwide for water treatment. This study investigates processing Moringa oleifera seeds to concentrate the bio-active constituents which have coagulation activity. Moringa oleifera seeds were processed for oil extraction using electro thermal soxhlet. Isolation and purification of bio-active constituents using chromatography technique were used to determine the molecular weight of the bio-active constituents. The molecular weight of bio-active constitu-ents found to be in a low molecular weight range of between 1000 – 6500 Dalton. The proposed method to isolate and purify the bio-active constituents was the cross flow filtration method, which produced the natu-ral coagulant with very simple technique (oil extraction;salt extraction;and microfiltration through 0.45 μm). The turbidity removal was up to 96.23 % using 0.4 mg/L of processed Moringa oleifera seeds to treat low initial turbidity river water between 34-36 Nephelometric Turbidity Units (NTU) without any additives. The microfiltration method is considered to be a practical method which needs no chemicals to be added com-pared to other researchers proposed methods. The natural coagulant produced was used with low dosages to get high turbidity removal which considered to be a breakthrough in this study and recommended to be scaled up for industry level. The product is commercially valuable at the same time it is minimizing the cost of water treatment.

Water Quality from the Purification Unit of Thiakhar (Diourbel, Senegal) and Impact of Discharges from Treatment on Water Resources

The installation of a purification unit since 2008 in the village of Thiakhar has improved the physico-chemical and bacteriological quality of the water supply. However about 55% of the raw water comes out of the unit as discharges (approximately 14 m3 per day) highly concentrated in fluoride and chloride ions. Based on historical samples, we find that the volumes of water consumed together with the volumes of water discharged are increasingly significant from year to year. The storage of waste water is carried out in a septic tank connected to a leaking cesspool sink. Significant excesses of these discharges are visible on the site and a flow of concentrate is observed creating a puddle of water that attracts birds and straying cattle. The study describes the following substantial impacts on the natural and human environment: 1) contamination of groundwater, 2) soil salinization 3), impact on flora and fauna, 4) impact on health. The study concludes by identifying measures to mitigate the negative impacts related to the discharges and by proposing alternative solution.

One-Step Reverse Osmosis Based on Riverbank Filtration for Future Drinking Water Purification

The presence of newly emerging pollutants in the aquatic environment poses great challenges for drink-ing water treatment plants.Due to their low concentrations and unknown characteristics,emerging pol-lutants cannot be efficiently removed by conventional water treatment processes,making technically,economically,and environmentally friendly water purification technologies increasingly important.This article introduces a one-step reverse osmosis(OSRO)concept consisting of riverbank filtration(RBF)and reverse osmosis(RO)for drinking water treatment.The OSRO concept combines the relatively low-cost natural pretreatment of river water with an advanced engineered purification system.RBF pro-vides a continuous natural source of water with stable water quality and a robust barrier for contami-nants.With the pre-removal of particles,organic matter,organic micro-pollutants(OMPs),and microbes,RBF becomes an ideal source for a purification system based on RO membranes,in comparison with the direct intake of surface water.OSRO treatment removes almost 99.9%of the particles,pathogens,viruses,and OMPs,as well as the vast majority of nutrients,and thus meets the requirements for the chlorine-free delivery of drinking water with high biostability.The OSRO treatment is cost effective com-pared with the standard conventional series of purification steps involving sprinkling filters,softening,and activated carbon.Artificial bank filtration(ABF),which functions as an artificial recharge in combi-nation with a sand filtration system,is proposed as an alternative for RBF in the OSRO concept to supply drinking water from locally available resources.It is also suggested that the OSRO concept be imple-mented with wind power as an alternative energy source in order to be more sustainable and renewable.An OSRO-based decentralized water system is proposed for water reclaiming and reuse.It is suggested that future water treatment focus on the combination of natural and engineered systems to provide drinking water through technically efficient,financially feasible,resource reusable,and environmentally relevant means.

Removal of Stabilized Silver Nanoparticles from Surface Water by Conventional Treatment Processes

Engineered nanomaterials are used in many applications, including pollution sensors, photovoltaics, medical imaging, drug delivery and environmental remediation. Due to their numerous applications, silver nanoparticles (Ag NPs) are receiving a large amount of attention. Ag NPs may occur in drinking water sources either during manufacturing, consumption and/or disposal processes. This potentially leads to the presence of Ag NPs in finished drinking water, which could have public health impacts. The objective of this research was to investigate the removal of several types of stabilized Ag NPs by potable water treatment processes. Specifically, this research achieved these objectives through: 1) Synthesis of Citrate-reduced Ag NPs, Polyvinylpyrrolidone stabilized (PVP) Ag NPs and Branched polyethyleneimine stabilized (BPEI) Ag NPs, 2) Characterization of synthesized Ag NPs to determine their aggregation potential, Zeta potential profiles, (pHpzc) and obtain morphological data from SEM images, and 3) An evaluation of the efficacy of conventional water treatment processes (i.e., coagulation, flocculation, sedimentation and sand filtration) in removing stabilized Ag NPs from natural water. The three NPs were found to be stable at the nano size in natural water. Alum coagulation had no impact on the PVP and BPEI Ag NPs. Flocculation and settling were found to be key steps for removal of these NPs. The three Ag NPs were not permanently removed by means of conventional water treatment processes employed in this study.

Quantitative Detection of <i>Helicobacter pylori</i>by Real Time PCR in Drinking Water—Environmental and Public Health Risk Significance

Helicobacter pylori (H. pylori) is bacteria considered to be present in half of the population and it is a public health problem worldwide. Most patients infected with H. pylori show no clinical symptoms;nonetheless, approximately 10% to 20% of these patients will develop peptic ulcers and 1% will develop gastric cancer. The International Agency for Research on Cancer has classified H. pylori as a Group 1 carcinogen, recognized as the only bacteria capable of producing cancer. Samples of drinking water (n = 44) from aqueducts with chlorination treatment in selected areas with high prevalence of gastric cancer were analyzed in Costa Rica. Samples of drinking water from Panamá (n = 44) from aqueducts supplying untreated water for human consumption in the province of Chiriquí were also analyzed. The molecular marker of H. pylori, glmM, was used, and to optimize the Real Time PCR (qPCR) technique, annealing temperature, concentration of primers and probe were standardized;also, by analyzing different standard curves, the best reaction conditions that allowed detecting and quantifying the gene were determined. The LightCycler&reg 480 II (LC480II) equipment from Roche Diagnostics GmbH was used, as well as the Absolute Quantification Analysis by means of the Second Derivative Maximum Method. In the case of the samples from Costa Rica, it was determined that 79.5% were positive for H. pylori;removing outlier high average, quantification of bacteria was determined in 3.6 × 103 copies/100 mL. For Panamá it was determined that 86% of the samples were found positive for the presence of H. pylori;removing outlier high average quantification of bacteria was determined at 3.3 × 102 copies/100 mL. The difference in values between the aqueducts in both countries revealed an environmental distribution of the bacteria of epidemiological interest in each case.