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Some disinfection by-products (DBPs) in drinking water present a potential safety concern. This study focuses on the elements influencing DBPs formation. A total of 120 water samples were collected from 10 different drinking water facilities spanning 5 counties within Huzhou, Zhejiang Province, China. Concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) were observed to be 14.5 and 27.4 μg/L, respectively, constituting 34 and 64% of the total DBPs. Seasonal fluctuations demonstrated that HAAs, THMs, halonitromethanes (HNMs), and haloacetonitriles (HANs) followed a similar pattern with higher levels in summer or autumn compared to spring. Importantly, the concentrations of HAAs and THMs were markedly higher in Taihu-sourced water compared to other sources. Geographically, Nanxun exhibited the highest levels of total DBPs, HAAs, and THMs, while Deqing and Changxing demonstrated significantly lower levels. Correlation studies between water quality parameters and DBPs revealed that factors such as chloride content, temperature, and residual chlorine positively influenced DBPs formation, whereas turbidity negatively affected it. Principal component analysis suggested similar formation processes for HANs, haloketones (HKs), HNMs, and THMs. Factors such as temperature, chemical oxygen demand (COD), and residual chlorine were identified as significant contributors to the prevalence of HAAs. [ABSTRACT FROM AUTHOR]

In this study, Moringa seeds, aloe vera leaves, and cactus leaves were used as biocoagulants for the treatment of drinking water. The effects of coagulant type, coagulant dosage, and pH were studied on the quality of the treated water. Response surface methodology was used to predict and optimize the parameters. The standard Six Jar test was used to measure the performance of coagulants. Three mixing modes were used in the jar test: quick mixing at 1 min at 120 rpm, slow mixing for 19 min at 40 rpm, and 15 min settling. The characterization results showed that extracts of Moringa seeds, aloe vera leaves, and cactus leaves contain 43.95 + 0.49, 13.9 + 0.42, and 10.94% + 0.37 protein, respectively. It was revealed that coagulant type, coagulant dosage, and the interaction between (coagulant type (MS-SC and AV-SC) and pH) were significant (p, 0.05) for turbidity removal. Jar test results showed a removal efficiency of turbidity 98.83%, and 98.74% and 69.83% using MS-SC, and AV-SC and Ca-SC bio, respectively. These results imply that the three coagulants can be considered as effective, lowcost, and eco-friendly resources for the treatment of drinking water in rural communities of Ethiopia where access to clean water is scarce. [ABSTRACT FROM AUTHOR]

The limiting factor in wide-scale application of membranes for wastewater treatment is membrane fouling. Coagulation has emerged as an effective technique for fouling control. In this research, municipal wastewater was treated using a two-stage treatment. In stage-1, chemically enhanced primary treatment (CEPT) was rendered using an optimum dose of two coagulants, i.e. alum, ferric chloride and a 1:1 mix of both. The optimum doses for coagulants were determined using a jar test. In stage-2, a nanofiltration (NF) membrane was used to further treat the effluent from stage-1. In CEPT, the 1:1 mixture of coagulants showed maximum removals, i.e. 75–77% for the total suspended solids and 73–75% for the chemical oxygen demand (COD). Stage-2 provided 85–95% removals for turbidity (0.88 nephelometric turbidity units), COD (41 mg/L), total dissolved solids (101 mg/L), hardness (11 mg/L as CaCO3), chlorides (80 mg/L), and heavy metals (copper [0.03 mg/L] and lead [0.02 mg/L]). The operational time of the NF membrane was 46 min, 55 min and 70 min using alum, ferric chloride, and mix (1:1), respectively. Significant reduction was observed in membrane fouling for 1:1 mixture of coagulants. The effluent met the US Environmental Protection Agency guidelines for non-potable reuse. HIGHLIGHTS Coagulants (alum and ferric chloride) give best results when used in a 1:1 mix.; Up to 95% removal of turbidity, COD, TDS, and heavy metals using chemically enhanced primary treatment and nanofiltration.; CEPT is an effective technique for NF membrane fouling control.; NF membrane run time is 1.5 and 1.3 times higher when coagulants are used in a mix rather than when used separately.; Effluent met the USEPA guidelines for non-potable reuse.;

Coagulation and flocculation processes play a major role in surface water treatment. The aim of this study was to eliminate the rapid mixing unit in the water treatment plant. This experimental study was conducted on turbid water. Turbid water was synthesized by kaolin powder. The conventional jar test method was used. The flocculation and sedimentation processes were performed on the turbid water without a rapid mixing unit for getting the new optimal condition. When the PACl coagulant was used alone and in conjunction with chitosan, the percentages of turbidity removal in low, medium and high turbidities were obtained as 86.7%, 95.8%, 97.8% and 86.67%, 95.73%, 98.26%, respectively. When the rapid mixing unit was emitted, the efficiency of turbidity removal in the low turbidity was reduced from 5.26% to 21.73%. But, in higher turbidity in two states (presence and absence of the rapid mixing units) it did not have a significant difference. This study showed that the removal of the rapid mix unit on the removal efficiency of turbidity in the low turbidity is effective, but does not have an effect on higher turbid water. Also, using PACl in conjunction with chitosan was effective in the removal efficiency and to reduce residual aluminum. HIGHLIGHTS To decrease the cost of water treatment.; Changing the process related to coagulation and flocculation stages.; To decrease the time and the consumed coagulant.; To increase efficiency of turbidity removal.; Simplicity of process.;

Turbidity reduction by coagulation-flocculation in drinking water reduces microbes and organic matter, increasing effectiveness of downstream treatment. Chitosan is a promising household water coagulant, but needs parameters for use. This study tested the effects of chitosan dose, molecular weight (MW), degree of deacetylation (DD), and functional groups on bentonite and kaolinite turbidity reduction in model household drinking water. Higher MW or DD produced greater reductions. Highest reductions were at doses 1 and 3 mg/L by MW >50,000 or >70% DD (residual turbidity <5 NTU). Higher doses did not necessarily continually increase reduction. For functional groups, 3 mg/L produced the highest reductions by lactate, acetate, and HCl, and lower reductions of kaolinite than bentonite. Doses where the point of zero charge was observed clustered around 3 mg/L. Chitosan reduced clay turbidity in water; effectiveness was influenced by dose, clay type, MW, DD, and functional groups. Reduction did not necessarily increase with MW. Bentonite had a broader effective dose range and higher reduction at the optimal dose than kaolinite. Chitosans with and without functional groups performed similarly. The best of the studied doses was 3 mg/L. Chitosans are promising for turbidity reduction in low-resource settings if combined with sedimentation and/or filtration. [ABSTRACT FROM AUTHOR]

This study has been carried out to evaluate the applicability of the pilot scale hybrid type of stormwater runoff treatment system for treatment of combined sewer overflow. Also, to determine the optimum operation parameter such as coagulation dosage concentration, effectiveness of coagulant usage, surface loading rate and backwashing conditions. The pilot scale stormwater filtration system (SFS) was installed at the municipal wastewater plant serving the city of Cheongju (CWTP), Korea. CWTP has a capacity of 280,000 m³/day. The SFS consists of a hydrocyclone coagulation/flocculation with polyaluminium chloride silicate (PACS) and an upflow filter to treat combined sewer overflows. There are two modes (without PACS use and with PACS use) of operation for the SFS. In case of no coagulant use, the range of suspended solids (SS) and turbidity removal efficiency were 72.0-86.6% (mean 80.0%) and 30.9-71.1% (mean 49.3%), respectively. And, the recovery rate of filter was 79.2-83.6% (mean 81.2%); the rate of remaining solid loading in filter media was 16.4-20.8% (mean 18.8%) after backwashing. The influent turbidity, SS concentrations were 59.0-90.7 NTU (mean 72.0 NTU), 194.0-320.0 mg/L (mean 246.7 mg/L), respectively. The range of PACS dosage concentration was 6.0-7.1 mg/L (mean 6.7 mg/L). The range of SS and turbidity removal efficiency was 84.9-98.2 (mean 91.4%) and 70.7-96.3 (mean 84.0%), respectively. It was found that removal efficiency was enhanced with PACS dosage. The recovery rate of filter was 92.0-92.5% (mean 92.3%) the rate of remaining solid loading in filter media was 6.1-8.2% (mean 7.2%) after backwashing. In the case of coagulant use, the particle size of the effluent is bigger than influent particle size. The results showed that SFS with PACS use more effective than without PACS use in SS and turbidity removal efficiency and recovery rate of filter. [ABSTRACT FROM AUTHOR]

A laboratory investigation of the treatment potential of a coagulation process in the context of stormwater treatment was undertaken. The initial 25 L road runoff generated from four rain events was collected and subjected to a jar-testing regime with two commercial coagulants. The treatment effect was assessed by analysing the runoff before and after treatment for turbidity, suspended solids and metal content. The coagulation process resulted in particle and total metal reduction of more than 90% compared to 40% for only sedimentation. Up to 40% reduction of dissolved Cr, Cu and Pb was also observed compared to 0% for sedimentation. This study shows that coagulation may be a useful process for stormwater treatment systems when the treatment requirements are high. [ABSTRACT FROM AUTHOR]

The seed of Moringa oleifera (MO) is a well-known coagulant used in water and wastewater treatment, especially in developing countries. The main mechanism of MO seed extract in coagulation is the positive protein component for charge neutralization. The method for efficient extraction of MO seed is very important for high coagulation activity. In this study, the effects of extraction mixing speed and extraction time of MO on coagulation activity were evaluated using a distilled water extraction method. Although the rotation per minute for extraction did not affect the coagulation efficiency, the extraction time strongly affected the coagulation efficiency of the extract. To evaluate the characteristic change of MO extract by extraction time, the charge of MO extract and protein characteristic in MO extract were analysed. As the extraction time was short, more positive charge and higher protein content were observed. For detailed protein analysis, the fluorescence spectroscopic study (EEM analysis) was performed. The tryptophan-like peak increased at longer extraction times. For efficient extraction of MO seed, a short extraction time is strongly recommended. [ABSTRACT FROM AUTHOR]

This work is about organic matter removal from Sidi Bel Abbes wastewater plant (Algeria) by coagulation on pillared clays (PILCs) under pH and PZC (point of zero charge), conditions. Two pillared clays, M/Al-PILCs (M¼ Fe or Mn), were synthesized, characterized, and studied as coagulants. Results showed that Fe/Al-pillared clay exhibits superior efficiency, with 18% higher removal rate than the common coagulants alum (AS) and ferric chloride (FCl), and that sedimentation time has positive effect on turbidity removal, with 95.85% removal rate during 30 min. Moreover PILCs will not cause pH go down too low, which is an advantage for achieving the best overall treatment. The IR and UV bands' reduction reveals the breakdown fragmentation of high molecular weight organic substances into smaller units. The highest total organic carbon (supercritical water oxidation analysis) and chemical oxygen demand adsorption capacities (48.52% and 61.85% respectively) obtained for Fe/Al-PILC can be related to increased basal spacing between adjacent layers, creating favorable adsorption sites in the microporous system. The suggested adsorption mechanism involves strong interactions between pollutants and PILCs leading to PILC-pollutant complex formation. [ABSTRACT FROM AUTHOR]

Dye wastewater has attracted significant attention because of its wide pH range and high content of color. In this work, the coagulation performances of cucurbit[8]uril for the removal of color from acid red 1 (AR1), orange II (OII), and Congo red (CR) dye wastewaters were investigated. Experimental results showed that color removal rates of greater than 95% for AR1, OII and CR were achieved at pH 6.0, when the dosage of cucurbit[8]uril was 1.51, 3.01 and 0.38 mmol·L-1, respectively. Under identical conditions, the color removal efficiencies of AR1 and CR were higher than OII, due to the larger molecular weights and more active hydroxyl and amino groups. Moreover, steady increases in AR1, OII and CR removal rates were recorded with increasing ionic strength. Such increases may be related to the reduction in thickness of the surface solvent membrane surrounding the dye colloids at high ionic strengths. Furthermore, Fourier transform infrared spectra demonstrated that no new bonds or functional groups were formed during coagulation, which indicates that the removal of AR1, OII and CR was primarily a physical process. The hydrogen bonds and inclusion complexes formed between cucurbit[8]uril and AR1, OII and CR contributed to the removal of color in coagulation predominantly. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the performance of a novel coagulant, i.e. ZrOCl2, for the removal of anthraquinone-based reactive dye fromaqueous solution. An ideal experimental setup was designed based on central composite design using response surface methodology to determine the individual and interactive effects of different operational variables (i.e. pH, coagulant dose and dye concentration) on treatment performance in terms of dye and chemical oxygen demand (COD) removal efficiencies. Total 92.58% dye and 85.33% COD removal were experimentally attained at optimized conditions at low coagulant dose, i.e. 156.67 mg/L for the dye concentration of 105.67 mg/L at pH 2. To validate the working pH of the metal coagulant, the static charge of ZrOCl2 was measured using Eh value. The performance of the coagulant was validated with experimental and predicted values in the selected data set, and R² values for both responses were found to be 0.99 and 0.95 respectively, which shows the reliability of the experimental design. Further, the toxicity of the coagulant was assessed and no such toxicity was found even up to the concentration of 500 mg/L, proclaiming the disposal of sludge may not exhibit any threat to humans. Experimental results suggested that the ZrOCl2 could be used as an eco-friendly coagulant for dye wastewater treatment. [ABSTRACT FROM AUTHOR]

In the present study, nine coagulants having potential to be used for sewage treatment were compared to assess their efficiency in removing total coliform bacteria, Escherichia coli and adenovirus. The coagulants tested were metallic and organic and their efficiency was compared when treating samples of rawand treated sewage (activated sludge). Before the efficiency tests of the coagulants, viral concentrationmethods were compared. Coagulation testswere carried out by using the jar-test system and the doses used ranged from100 ppmto 1,000 ppm. Viral DNA was extracted and subjected to real-time polymerase chain reaction (qPCR) using primers for the gene of AdV hexon. Aluminum sulfate (1,000 ppm) presented the best results for raw sewage among metal coagulants whereas Acquapol® C118 and WW (1,000 ppm) had themost satisfactory resultsamong organic coagulants, both reducing up to 7 logs for coliforms and 4 logs for virus. For the treated effluent, FeCl2 (1,000 ppm) presented best results for metal coagulants, whereas, from organic coagulants, the best removal rates were for Acquapol® 893/11 (1,000 ppm), both reducing up to 3 logs for coliforms and 4 logs for virus. [ABSTRACT FROM AUTHOR]

The required coagulant dosage is strongly related to the quality of raw water or wastewater. Online sensors for most quality parameters are now readily available to treatment facilities, yet remain rarely used in treatment process control. This paper presents the evaluation of an advanced coagulant dosing control system based on online measurements in full-scale processes. The popular multivariate analytical method, partial least square regression, was used to build up the relationship between the coagulant dose and wastewater quality. The system was tested in two wastewater treatment plants (WWTPs) in Norway. Coagulant savings up to 30% in Norwegian plants were observed with feed forward calibrations. The considerable savings reduce sludge production, leading to further cost saving on sludge treatment. This paper presents the method, function and experiences of the full-scale implementation of the system in different WWTPs. [ABSTRACT FROM AUTHOR]

A composite coagulant polyferric magnesium silicate (PFMSi) was synthesized by co-polymerization. The structure and morphology of PFMSi were characterized by X-ray diffraction, Fourier transform infrared spectra and scanning electron microscope microphotographs; meanwhile, the coagulation efficiency was evaluated under different ratios of Fe/Si, Mg/Si, basicity ([OH]/7491;M] ratio), and dosage. The results suggested that the PFMSi coagulant shows an amorphous phase structure, and new chemical compounds had been formed; simultaneously, the different preparation conditions had major effects on coagulation performance. Additionally, the raw water collected from Pearl River was used as a treated water sample to verify the coagulation efficiency of PFMSi. Overall, it is suggested that PFMSi is an efficient coagulant in the removal of turbidity, UV254 and total organic carbon, and it shows a markedly better coagulation performance than polymeric aluminium and non-modified coagulant. The study of coagulation kinetics and zeta potential showed that adsorption-bridging was the main mechanism for the introduction of silicon [ABSTRACT FROM AUTHOR]

With the purpose of improving the ultrafiltration (UF) efficiency, anionic polyacrylamide (APAM) has been used as a coagulant aid in the flocculation-UF process. In this study, the impact of APAM on UF efficiency has been investigated with regard to membrane fouling, membrane cleaning and effluent quality. The results indicated that the optimal dosage of APAM had positive impacts on membrane fouling control, membrane cleaning and effluent quality. According to the flux decline curve, scanning electron microscopy and contact angle characterization, the optimal dosage of APAM was determined to be 0.1 mg/L coupled with 2 mg/L (as Al3þ) poly-aluminium chloride. Under this optimal condition, membrane fouling can be mitigated because of the formation of a porous and hydrophilic fouling layer. APAM in the fouling layer can improve the chemical cleaning efficiency of 0.5% NaOH due to the disintegration of the fouling layer when APAM is dissolved under strong alkaline conditions. Furthermore, with the addition of APAM in the flocculation-UF process, more active adsorption sites can be formed in the flocs as well as the membrane fouling layer, thus more antipyrine molecules in the raw water can be adsorbed and removed in the flocculation-UF process. [ABSTRACT FROM AUTHOR]

More efficient plant utilisation of the phosphorus (P) in sewage sludge is required because rock phosphate is a limited resource. To meet environmental legislation thresholds for P removal from wastewater (WW), primary treatment with iron (Fe) or aluminium (Al) coagulants is effective. There is also a growing trend for WW treatment plants (WWTPs) to be coupled to a biogas process, in order to co-generate energy. The sludge produced, when stabilised, is used as a soil amendment in many countries. This study examined the effects of anaerobic digestion (AD), with or without liming as a post-treatment, on P release from Fe- and Al-precipitated sludges originating from primary WWTPs. Plant uptake of P from Fe- and Al-precipitated sludge after lime treatment but without AD was also compared. Chemical characterisation with sequential extraction of P and a greenhouse experiment with barley (Hordeum vulgare) were performed to assess the treatment effects on plant-available P. Liming increased the P-labile fraction in all cases. Plant P uptake increased from 18.5 mg pot-1 to 53 mg P pot-1 with liming of Fe-precipitated sludge and to 35 mg P pot-1 with liming of the digestate, while it increased from 18.7 mg pot-1 to 39 and 29 mg P pot-1 for the Al-precipitated substrate and digestate, respectively. Thus, liming of untreated Fe-precipitated sludge and its digestate resulted in higher P uptake than liming its Al-precipitated counterparts. AD had a negative impact on P mobility for both sludges. [ABSTRACT FROM AUTHOR]

The effects of temperature, storage time and water pH on the coagulation performance of okra seed protein in water treatment were assessed. In a jar test experiment, okra salt extract achieved a notable improvement in treatment efficiency with storage time and showed good performance in quality after thermal treatment at 60, 97 and 140 °C temperatures for 6, 4 and 2 hours, respectively. The performance improvement of more than 8% is considered to be due to the denaturation and subsequent removal of coagulation-hindering proteins in okra seed. Furthermore, the results of a sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis show two distinctive bands of protein responsible for the coagulation process after denaturation. It was further shown that at optimal coagulant dose, the pH of the treated water remained unaffected as a result of the protein's buffering capability during coagulation. Therefore, denatured okra seed exhibited improved performance compared to the native crude extract and offers clear benefits as a water treatment coagulant. [ABSTRACT FROM AUTHOR]

Alum recovery from water treatment sludge is a promising technique applied to decrease usage of fresh coagulants in the water treatment industry. In addition, alum recovery reduces sludge volume for easy handling. The undertaken work investigated the parametric conditions for alum recovery procedure by acidification. The results show that alum recovery reaches up to 69.03%, and the reduction of sludge volume reaches its highest level at 90%. Moreover, results of the parametric investigation reveal that the mixing time of 60 minutes and mixing intensity of 150 rpm are the optimum conditions of mixing for alum recovery from water treatment sludge. The optimum pH level is 1.50 for alum recovery as indicated by maximum aluminum releasing, maximum reduction of sludge volume, and reasonable dosages of added sulfuric acid. [ABSTRACT FROM AUTHOR]

Primary and chemically enhanced primary wastewater treatment with microsieving (disc or drum filtration) was studied at the large pilot scale at seven municipal wastewater treatment plants in Europe. Without chemical dosing, the reduction of suspended solids (SS) was (on average) 50% (20-65%). By introducing chemically enhanced primary treatment and dosing with cationic polymer only, SS removal could be controlled and increased to >80%. A maximum SS removal of >90% was achieved with a chemical dosing of >0.007 mg polymer/mg influent SS and 20 mg Al3+/L or 30 mg Fe3+/L. When comparing sieve pore sizes of 30-40 µm with 100 µm, the effluent SS was comparable, indicating that the larger sieve pore size could be used due to the higher loading capacity for the solids. Phosphorus removal was adjusted with the coagulant dose, and a removal of 95-97% was achieved. Moreover, microsieving offers favourable conditions for automated dosing control due to the low retention time in the filter. [ABSTRACT FROM AUTHOR]

Chitosan was chosen as an alternative primary coagulant in a complementary coagulation- flocculation treatment of sanitary landfill leachate with the aim of removing recalcitrant organic matter. In order to optimize the process conditions, central composite design and response surface methodology were applied. To evaluate the performance of the process using chitosan, we also carried out tests with aluminium sulphate (Al2 (SO4)3.14 H2O) as coagulant. In addition, acute toxicity tests were carried using the duckweed Lemna minor and the guppy fish Poecilia reticulata as test organisms. The analytic hierarchy process was employed for selecting the most appropriate coagulant. Mean values of true colour removal efficiency of 80% and turbidity removal efficiency of 91.4% were reached at chitosan dosages of 960 mg L–1 at pH 8.5. The acute toxicity tests showed that organisms were sensitive to all samples, mainly after coagulation–flocculation using chitosan. CE50 for L. minor was not determined because there was no inhibition of the average growth rate and biomass production; LC50 for P. reticulata was 23% (v v–1). Multi-criteria analysis showed that alum was the most appropriate coagulant. Therefore, chitosan as primary coagulant was not considered to be a viable alternative in the post-treatment of landfill leachate. [ABSTRACT FROM AUTHOR]

We investigated the effect of coagulant basicity on bacteriophage removal from river water by polyferric chloride (PFC). PFC at three basicities (basicity 0.9-2.1) was prepared by means of base titration (NaOH was added to ferric chloride (FeCl3) solution) and the virus removal efficiencies of those PFCs were compared with that of FeCl3 (basicity 0). The virus removal efficiencies of the PFCs were equal to or less than that of FeCl3 at both pH 6 and pH 8. This suggests that, unlike aluminumbased coagulants, increasing the basicity of iron-based coagulants does not improve virus removal efficiency. Furthermore, the relative abundance of monomeric iron(III) species in the PFCs decreased, whereas that of precipitated iron(III) species increased with increasing basicity, as assessed with a ferron method. Colloid charge density also decreased with increasing basicity. Therefore, it is likely that the reduction in the abundance of monomeric iron(III) species led to the reduction in colloid charge density, which then reduced virus removal efficiency. Thus, the development of novel ironbased coagulants with increased virus removal efficiency may not be possible by simply increasing the basicity of the coagulant. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) absorption characteristics of poly-Al-Zn-Fe (PAZF), a polymerized coagulant containing three kinds of metallic elements prepared from a galvanized-aluminum slag, was analyzed by UV-visible spectrophotometry during its polymerization process. Pollutant removal by PAZF in treating various wastewaters was investigated, in comparison with that of polyaluminum chloride (PAC). The results showed that PAZF can be applied to different wastewaters and had excellent coagulation behavior due to its special internal composition. Various complicated substances having different absorption wavelengths and polymeric properties were produced during the PAZF polymerization process, and the structures of these complicated substances were adjusted continuously with the increasing of the polymerization time. PAZF posed better turbidity and organic matter (chemical oxygen demand, CODCr) removal than PAC for different wastewaters, and the required dosage of PAZF was far lower than that of PAC when achieving the same coagulation performance. For pharmaceutical, sugar, dyeing, simulated pesticide and landscape wastewaters, PAZF gave higher removal of turbidity or CODCr than PAC, by up to 79.5% (coagulant dose: 74 mg/L) or 16% (148 mg/L), 13.4% (111 mg/L) or 10% (185 mg/L), 26.5% (148 mg/L) or 8.1% (18.5 mg/L), 40% (18.5 mg/L) or 13.4% (111 mg/L), and 5% (70 mg/L) or 5% (70 mg/L), respectively. [ABSTRACT FROM AUTHOR]

Membrane fouling can be significantly mitigated through circulating coagulation, floc breakage and re-growth under appropriate conditions. In this study, unified membrane filtration index (UMFI) was adopted to analyze the membrane fouling. The effect of circulating coagulation pretreatment on both flocs' average diameter and membrane fouling were investigated under different concentrations of coagulant and reflux flocs. When the concentrations of coagulant and reflux flocs were 6 and 10 mg/L, respectively, the average diameter of flocs and UMFI were 565.416 µm and 0.0004. Floc breakage and re-growth existed in the aeration cleaning; circulating coagulation was conducive to the flocs' re-growth and recombination. The recovery rate of flocs' average diameter could reach 90%. In circulating coagulation-membrane filtration process, flocs underwent re-growth and the characteristic of flocs changed which made size distribution uniform, slowed down the growth of transmembrane pressure and mitigated membrane fouling. [ABSTRACT FROM AUTHOR]

Filtration efficiency in a conventional water treatment system was analyzed in the context of pre-hydrolyzed coagulant overdosing. Two commercial coagulants of different aluminum speciation were tested. A study was carried out at a water treatment plant supplied with raw water of variable quality. The lack of stability of water quality caused many problems with maintaining the optimal coagulant dose. The achieved results show that the type of coagulant had a very strong influence on the effectiveness of filtration resulting from the application of an improper coagulant dose. The overdosing of high basicity coagulant (PAC85) caused a significant increase of fine particles in the outflow from the sedimentation tanks, which could not be retained in the filter bed due to high surface charge and the small size of hydrolysis products. When using a coagulant of lower basicity (PAC70), it was much easier to control the dose of coagulant and to adjust it to the changing water quality. [ABSTRACT FROM AUTHOR]

Total photosynthetic pigments (TPP) or chlorophyll-a analysis can be useful in selecting coagulant treatments that will improve phytoplankton removal and reduce treatment costs. The objectives of this study were to compare the efficacy of phytoplankton and turbidity removal when using TPP and turbidity as indicator parameters of appropriate coagulant treatments as well as to evaluate the cost impacts thereof. During seven different sampling occasions, source water samples with substantially different TPP and turbidity contents were collected from two South African freshwater sources (Benoni Lake and Vaal Dam) to conduct jar stirring tests. After sedimentation, TPP and turbidity analyses were performed to assess the efficacy of coagulant treatments (Ca(OH)2-SiO2, Ca(OH)2-organic polymer and organic polymer). Results showed that TPP analysis is indeed a useful indicator parameter to consider purifying source water enriched with phytoplankton. Ca(OH)2-organic polymer treatment was more costly than Ca(OH)2-SiO2 and organic polymer, but the only coagulant treatment that met the removal criteria after sedimentation. Benoni Lake source water (TPP: 34.29 µg/l; 4.29 NTU) was more costly to treat than Vaal Dam source water (TPP: 2.29 µg/l; 80.29 NTU). Findings made from this study confirm that high phytoplankton concentrations in source water due for treatment will increase the treatment costs. [ABSTRACT FROM AUTHOR]

This paper considers the removal of dissolved organic carbon (DOC) from a typical UK upland reservoir water using three different coagulants; aluminium sulphate/alum (Al2(SO4)3(aq)), polyaluminium chloride/PAX-18 (Aln(OH)mCl3n-m(aq)) and ferric sulphate/PIX-322 (Fe2(SO4)3(aq)). A comparison of DOC quality including fractional character, colour, specific ultraviolet absorption (SUVA) and molecular weight was made between the source water and the supernatants obtained following its coagulation in each case. Trihalomethane formation potential (THMFP) was compared before and after treatment to assess which coagulant performed best in terms of THM amelioration. The conditions (coagulant dose and pH) required to obtain optimal DOC removal were established using bench-scale jar tests. Statistically significant differences in DOC removal rates were observed between the different coagulants. THMFP removal was linked to a combination of high net DOC removal and the preferential removal of THM precursors. This selectivity may also be responsible for the increase in brominated THM species (BrTHMs) observed following treatment. [ABSTRACT FROM AUTHOR]

Wastewater is an important source of pathogenic enteric microorganisms in surface water and a major contaminating agent of drinking water. Although primary and secondary wastewater treatments reduce the numbers of microorganisms in wastewater, significant numbers of microbes can still be present in the effluent. The aim of this study was to test the feasibility of tertiary treatment for municipal wastewater treatment plants (WWTPs) using PIX (FeCl3) or PAX (AlCl3) coagulants and peracetic acid (PAA) the disinfectant to reduce microbial load in effluent. Our study showed that both PIX and PAX efficiently reduced microbial numbers. PAA disinfection greatly reduced the numbers of culturable indicator microorganisms (Escherichia coli, intestinal enterococci, F-specific RNA coliphages and somatic DNA coliphages). In addition, pathogenic microorganisms, thermotolerant Campylobacter, Salmonella and norovirus GI, were successfully reduced using the tertiary treatments. In contrast, clostridia, Legionella, rotavirus, norovirus GII and adenovirus showed better resistance against PAA compared to the other microorganisms. However, interpretation of polymerase chain reaction (PCR) analysis results will need further studies to clarify the infectivity of the pathogenic microbes. In conclusion, PIX and PAX flocculants followed by PAA disinfectant can be used as a tertiary treatment for municipal WWTP effluents to reduce the numbers of indicator and pathogenic microorganisms. [ABSTRACT FROM AUTHOR]

With their increasing use, nanoparticles will become concentrated in urban effluents in the future. Both adequate monitoring methods and water treatment technologies will be necessary to assess and avoid consumer exposure. This paper reports results in these two challenging areas for both organic and inorganic nanoparticles. Treatment experiments indicate that lamellar settling is better adapted than dissolved air flotation for SiO2 nanoparticles removal. The use of 120 mg/L of Aqualenc coagulant without flocculant addition allows 99% removal to be achieved for an initial concentration of 1 g/L. On the other hand, the dissolved air flotation process implemented under the usual industrial conditions does not permit removal of SiO2 nanoparticles. In this case SiO2 removal occurs only by settling in the flocculator tank. Application of a high resolution liquid chromatography/mass spectrometry (LC/MS) technique to a small selection of treated urban effluents indicates that C60 fullerenes are not yet widely distributed in effluents; however non-point sources cannot be entirely ruled out. [ABSTRACT FROM AUTHOR]

This paper describes the use of both the streaming current detector (SCD) and coagulation computer models to provide real-time data for required coagulant feed rates. The method for computer modeling of coagulation and other water treatment processes/operations was originally developed for Lake Michigan Filtration Plant in Grand Rapids, Michigan (MI). Since the initial implementation, a number of water treatment plants (WTPs) in the United States have begun routinely utilizing computer models for chemical feed control and process performance optimization. One plant, Holland WTP in Holland, MI, currently employs both an SCD and a coagulation computer model for chemical feed control. Case studies presented in this paper compare the performance of coagulation computer models and the SCD in full-scale operation. [ABSTRACT FROM AUTHOR]