Effects of coexisting anions on removal of bromide in drinking water by coagulation

Bromo-DBPs (disinfection by-products) are generated by bromide and disinfectant in drinking water disinfection, which have adverse effects on human health. In this study, effects of coexisting anions on removal of bromide by aluminium coagulation were investigated. It was observed that bromide was removed of 62.1-87.0% in raw water, while the removal efficiency of bromide was achieved 82.8-99.2% in deionized water through the combination of Br- with Al(III) in various pathways. The coexisting anions in raw water significantly affected the removal of bromide. Removal efficiency decreased by 11.5, 21.2, 14.6, 8.0 and 40.8% with the addition of HCO3-, SO4(2-), Cl-, NO3- and H2PO4-, respectively, for their affinities with Al(III) or accelerating the formation of Al(OH)3(am). These results demonstrated that bromo-DBPs in drinking water could be controlled though removing bromide by enhanced coagulation.     

Disinfection by-product precursors reduction by various coagulation techniques in Istanbul water supplies

Coagulation process can be used to control natural organic matter (NOM) during drinking water production. The effectiveness of the coagulation process appeared to depend on the pH of coagulation rather than coagulant dosages. Jar tests conducted with depressed pH levels at different coagulation conditions removed more dissolved organic carbon (DOC) than those at moderate pH levels. For low DOC waters, like Omerli Lake Water (OLW), additional treatment would be necessary to achieve enhanced removal of NOM. In this study, three different coagulation techniques were used to remove disinfection by-products (DBP) precursors from three Istanbul surface water supplies. Jar test results indicate that optimize coagulation (OC) can enhance the removal of DBP precursors, and the removal of DOC could be improved from the current average of 15% to an average of 56% at the three sites tested. At lower pH, ferric coagulants generally performed better for removal of DBP precursors than did alum.     

Coagulation/flocculation process and sludge conditioning in beverage industrial wastewater treatment

Attempts were made in this study to examine the effectiveness of coagulation and flocculation process using ferric chloride and polyelectrolyte (non-ionic polyacrylamide) for the treatment of beverage industrial wastewater. Removal of organic matter (expressed as chemical oxygen demand, COD), total phosphorus (TP) and total suspended solid (TSS) using ferric chloride and organic polyelectrolyte during coagulation/flocculation process were investigated. Also, the optimum conditions for coagulation/flocculation process, such as coagulant dosage, polyelectrolyte dosage, and pH of solution were investigated using jar-test experiment. The effect of different dosages of polyelectrolyte in combination with coagulant was also studied. The results revealed that in the range of pH tested, the optimal operating pH was 9. Percentage removals of 73, 95 and 97 for COD, TP and TSS, respectively, were achieved by the addition of 300mg/L FeCl(3).6H(2)O, whereas 91, 99 and 97% removal of COD, TP and TSS, respectively, were achieved with the addition of 25mg/L polyelectrolyte to 100mg/L ferric chloride. The volume of sludge produced, when ferric chloride was used solely, was higher compared to the use of combination of polyelectrolyte and FeCl(3).6H(2)0. The combined use of coagulant and polyelectrolyte resulted in the production of sludge volume with reduction of 60% of the amount produced, when coagulant was solely used for the treatment. It can be concluded from this study that coagulation/flocculation may be a useful pre-treatment process for beverage industrial wastewater prior to biological treatment.     

Feasibility investigation of oily wastewater treatment by combination of zinc and PAM in coagulation/flocculation

Poly-zinc silicate (PZSS) is a new type of coagulant with cationic polymer synthesized by polysilicic acid and zinc sulfate. It has been used in several sorts of wastewaters treatment, but not used in oily wastewater treatment. In this study, we investigated the coagulation/flocculation of oil and suspended solids in heavy oil wastewater (HOW) by PZSS and anion polyacrylamide (A-PAM). The properties of PZSS cooperated with A-PAM were compared with PAC and PFS in dosages, PAMs amount, settling time, pH value and flocs morphology. The results showed that PZSS was more efficient than PAC and PFS. Under the optimum experimental conditions of coagulation/flocculation (dosage: 100mg/L, A-PAM dosage: 1.0mg/L, settling time time: 40min and pH 6.5-9.5), more than 99% of oil was removed and suspended solid value less than 5mg/L by using PZSS cooperated with A-PAM, which could satisfy the demands of the pre-treatment process for HOW to be reused in the steam boiler or recycled into the injecting well.     

Advanced treatment of coking wastewater by coagulation and zero-valent iron processes

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5-31.8% could be achieved under the optimal condition of coagulation, i.e. 400mg/L of Fe(2)(SO(4))3 as coagulant at pH 3.0-5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10 g/L active carbon and 30 g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation-reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000 Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process.     

Inactivation of Chironomid larvae with chlorine dioxide

In this paper, comparative experiments on the inactivation of Chironomid larvae by chlorine dioxide and chlorine were conducted. In addition, batch experiments were performed in order to analyze the influence of pH value, organic precursor concentration and temperature on the inactivation efficiency of Chironomid larvae with chlorine dioxide. Based on it, removal effect of different pre-oxidation followed by coagulation process on Chironomid larvae in raw water was evaluated. The results showed that chlorine dioxide possessed better inactivation performance than chlorine, and complete inactivation of Chironomid larvae was obtained at CT value of 37.5 mg min/L (dose of 1.5mg/L and exposure time of 25 min). The pH in the range of 6-8 did not affect the inactivation efficiency of chlorine dioxide, whereas pH 10 resulted in around 10% decrease in inactivation rate. Meanwhile, the organic precursor had negative effects on inactivation, indicated by the decreased inactivation rate from 100% at TOC concentration of 0mg/L to 62.2% at 8 mg/L when the CT value was 45 mg min/L. With regard to the temperature, the inactivation efficiency of Chironomid larvae was significantly improved with the temperature increasing within the range investigated of 10-25 degrees C. The inactivation rate was reduced by 68.9% when temperature reduced from 25 degrees C to 10 degrees C. The coagulation jar test showed that Chironomid larvae in the raw water could be completely removed by chlorine dioxide pre-oxidation in combination with the coagulation process at CT value of 24.8 mg min/L.     

用混凝-超滤法处理低温低浊水

考察了采用混凝-超滤法处理低温低浊时期松花江水的中试试验效果,并与水厂常规处理水质进行了比较.试验结果表明:混凝-超滤法出水浊度恒低于0.3 NTU;投加20 mg/L聚合氯化铝,超滤膜对CODMn去除率达到50%~58%,膜出水色度为6~8度;此外,投加混凝剂可以使膜渗透性能得以改善.因此混凝-超滤法可以作为低温低浊水处理的有效方法.     

超滤膜净化水库水试验研究

用中空纤维超滤膜处理哈尔滨附近B水库水,以替代混凝、沉淀、砂滤的传统自来水生产方法,研究生产饮用水的新工艺.研究了原水温度、浊度、操作压力和混凝剂的加入量对膜通量的影响.研究发现超滤膜通量与膜进水浊度的对数成反比,跨膜压力增大、适当加入混凝剂,膜通量增加.超滤出水和传统工艺的出水进行了比较,超滤膜出水浊度小于0.2 NTU,明显好于传统工艺的出水浊度.对超滤处理后的出水水质进行了全分析,超滤对铁、铝、锰、色度、好氧量、总有机碳等均有较好的处理效果,完全满足饮用水水质的标准.     

Performance optimization of coagulant/flocculant in the treatment of wastewater from a beverage industry

This study investigated the effect of coagulation/flocculation treatment process on wastewater of Fumman Beverage Industry, Ibadan, Nigeria. The study also compared different dosages of coagulant, polyelectrolyte (non-ionic polyacrylamide) and different pH values of the coagulation processes. The effect of different dosages of polyelectrolyte in combination with coagulant was also studied. The results reveal that low pH values (3-8), enhance removal efficiency of the contaminants. Percentage removal of 78, 74 and 75 of COD, TSS and TP, respectively, were achieved by the addition of 500 mg/L Fe2(SO4)3.3H2O and 93, 94 and 96% removal of COD, TSS and TP, respectively, were achieved with the addition of 25 mg/L polyelectrolyte to the coagulation process. The volume of sludge produced, when coagulant was used solely, was higher compared to the use of polyelectrolyte combined with Fe2(SO4)3.3H2O. This may be as a result of non-ionic nature of the polyelectrolyte; hence, it does not chemically react with solids of the wastewater. Coagulation/flocculation may be useful as a pre-treatment process for beverage industrial wastewater prior to biological treatment.     

Treatment of palm oil mill effluent (POME) by coagulation flocculation process using peanut–okra and wheat germ–okra

Coagulation–flocculation has been proven as one of the effective processes in treating palm oil mill effluent (POME), which is a highly polluted wastewater generated from palm oil milling process. Two pairs of natural coagulant–flocculant were studied and evaluated: peanut–okra and wheat germ–okra. This research aims to optimize the operating parameters of the coagulation flocculation process in removing turbidity, total suspended solid and chemical oxygen demand (COD) from POME by using a central composite design in the Design Expert^® software. Important parameters such as operating pH, coagulant and flocculant dosages were empirically determined using jar test experiment and optimized using response surface methodology module. Significant quadratic polynomial models were obtained via regression analyses (R²) for peanut–okra (0.9355, 0.9534 and 0.8586 for turbidity, total suspended solids and COD removal, respectively) and wheat germ–okra (0.9638, 0.9578 and 0.7691 for turbidity, total suspended solids and COD removal, respectively). The highest observed removal efficiencies of turbidity, total suspended solids and COD (92.5, 86.6 and 34.8%, respectively, for peanut–okra; 86.6, 87.5 and 43.6%, respectively, for wheat germ–okra) were obtained at optimum pH, coagulant and flocculant dosages (pH 11.6, 1000.1 mg/L and 135.5 mg/L, respectively, for peanut–okra; pH 12, 1170.5 mg/L and 100 mg/L, respectively, for wheat germ–okra). The coagulation flocculation performance of peanut–okra and wheat germ–okra were comparable to each other. Characterizations of the natural coagulant–flocculant, as well as the sludge produced, were performed using Fourier transform infrared, energy-dispersive X-ray spectroscopy and field emission scanning electron microscope. More than 98% of water was removed from POME sludge by using centrifuge and drying methods, indicating that a significant reduction in sludge volume was achieved.     

混凝-微滤工艺提高饮用水生物稳定性的试验研究

以滦河水为处理对象,考察了混凝-微滤工艺对原水中营养物的去除效果和对饮用水生物稳定性的影响.该工艺对DOC的去除率随混凝剂投加量的提高而增加,在FeCl3投加量为2mg/L时,DOC的平均去除率达到22.4%.该工艺可有效去除可生物降解溶解性有机碳(BDOC)和总磷,并分别达到饮用水生物稳定性的阈值要求(BDOC<0.25mg/L和TP<5μg/L);同时,工艺出水的细菌再生长潜力(BRP)比原水降低1个数量级.因此采用混凝-微滤工艺可有效提高饮用水的生物稳定性,控制水中细菌再生长趋势.     

Phosphorus removal performance of acid mine drainage from wastewater

Acid mine drainage (AMD) in Yunfu iron sulfide mine contain Fe(2+), Fe(3+), and Al(3+) up to 8000, 1700 and 1200 mg/L, respectively. Phosphorus removal from synthetic wastewater with 10mg/L of total phosphorus (TP) concentration and second municipal effluent with 3.5-4.0mg/L of TP concentration were conducted with the AMD by jar tests. Dosage of the AMD and initial pH of water are the two most important parameters affecting the performance of phosphorus removal of the AMD. The optimal phosphorus removal efficiency and residual iron ions (TFe) concentration are 97.0% and 3.0mg/L, respectively, at 1.61 Fe/P molar ratio and pH 8.03 for synthetic wastewater, and 92.1% and 0.32 mg/L, respectively, for second municipal effluent at 1.41 Fe/P molar ratio and pH 7.3. Resultant heavy metal concentration in effluents and precipitate was very low, and the risk of resultant heavy metal contamination was very small. The phosphorus removal performance of the AMD was much similar to that of ferric sulfate (FS) and polyferric sulfate (PFS), and better than that of FeSO(4). And residual TFe concentration in treated water arising from utilization of the AMD was similar to that of FeSO(4), and higher than that of FS and PFS. The AMD could be used as coagulant for phosphorus removal from wastewater directly due to the presence of Fe(2+), Fe(3+), and Al(3+) largely.     

Aluminium sulfate as coagulant for highly polluted cork processing wastewaters: removal of organic matter

This is the first part of a work on the chemistry of aluminium as coagulant in the treatment of highly polluted cork processing wastewater. The main aim of this first part was to determine the removal of organic matter - measured by reductions in chemical oxygen demand (COD), polyphenols (TP), and aromatic compounds (A) - that can be obtained using this physicochemical process. To this end, jar-test experiments were carried out to determine the optimal conditions for the process, in particular, the effective aluminium dosage, contamination level of wastewater, coagulant mixing time, stirring speed, and pH. The ranges of tested parameters for the coagulation process were: coagulant dose (33-166 mgL(-1) of Al(3+)), contamination of the wastewater (COD between 1060 and 3050 mgO(2)L(-1)), mixing time (5-30 min), stirring speed (60-300 rpm) and pH (4-11). The resulting removal capacities were in the ranges of 20-55% for COD, 28-89% for polyphenols, and 29-90% for aromatic compounds. The best results were obtained with a coagulant mixing time of 5 min and a stirring speed of 300 rpm. The optimal choices of pH and coagulant dose fundamentally depended on the contamination level of wastewater.     

Optimization of coagulation-flocculation process for pulp and paper mill effluent by response surface methodological analysis

Coagulation-flocculation is a proven technique for the treatment of high suspended solids wastewater. In this study, the central composite face-centered design (CCFD) and response surface methodology (RSM) have been applied to optimize two most important operating variables: coagulant dosage and pH, in the coagulation-flocculation process of pulp and paper mill wastewater treatment. The treated wastewater with high total suspended solids (TSS) removal, low SVI (sludge volume index) and high water recovery are the main objectives to be achieved through the coagulation-flocculation process. The effect of interactions between coagulant dosage and pH on the TSS removal and SVI are significant, whereas there is no interaction between coagulant dosage and water recovery. Quadratic models have been developed for the response variables, i.e. TSS removal, SVI and water recovery based on the high coefficient of determination (R(2)) value of >0.99 obtained from the analysis of variances (ANOVA). The optimum conditions for coagulant dosage and pH are 1045mgL(-1) and 6.75, respectively, where 99% of TSS removal, SVI of 37mLg(-1) and 82% of water recovery can be obtained.     

微絮凝-砂滤-超滤处理淮河原水的试验研究

采用微絮凝-砂滤-超滤工艺对淮河原水进行了中试规模的试验．重点考察预处理条件如滤速和混凝剂投加量的变化对后续膜处理性能的影响．结果表明，试验工艺去除CODMn的效果随着混凝剂投加量的增加而提高．在投加量(大于4mg／L)不变的条件下，滤速的变化不会影响砂滤出水的浊度和CODMn，当投加量为4mg／L时，较高的滤速导致砂滤出水的浊度和CODMn的增加．由于后续超滤膜的截留作用，膜出水的浊度和CODMn令人满意．     

Application of psyllium husk as coagulant and coagulant aid in semi-aerobic landfill leachate treatment

Landfill leachate is a heavily polluted and a likely hazardous liquid that is produced as a result of water infiltration through solid wastes generated industrially and domestically. This study investigates the potential of using psyllium husk as coagulant and coagulant aid for the treatment of landfill leachate. Psyllium husk has been tested as primary coagulant and as coagulant aid with poly-aluminum chloride (PACl) and aluminum sulfate (alum). As primary coagulant, the optimum dosage and pH for PACl were 7.2 and 7.5 g/L, respectively, with removal efficiencies of 55, 80 and 95% for COD, color and TSS, respectively. For alum, the optimum conditions were 11 g/L alum dosage and pH 6.5 with removal efficiencies of 58, 79 and 78% for COD, color and TSS, respectively. The maximum removal efficiencies of COD, color and TSS were 64, 90 and 96%, respectively, when psyllium husk was used as coagulant aid with PACl. Based on the results, psyllium husk was found to be more effective as coagulant aid with PACl in the removal of COD, color and TSS as compared to alum. Zeta potential test was carried out for leachate, PACl, alum and psyllium husk before and after running the jar test to enhance the results of the jar test experiments.     

Removal of antibiotics by coagulation and granular activated carbon filtration

Treatment of seven tetracycline classes of antibiotic (TAs) from raw waters (synthetic and river) was evaluated using coagulation and granular activated carbon (GAC) filtration in this study. Both coagulation and GAC filtration were effective for removal of TAs, and the removal efficiency depended on the type of TAs. GAC filtration was relatively more effective for removal of tetracycline (TC), doxycycline-hyclate (DXC), and chlortetracycline-HCl (CTC), which were difficult to remove by coagulation. It was speculated that TAs would be removed through the charge neutralization and sweep coagulation when poly-aluminum chloride (PACl) was added into the raw waters. The charge neutralization of zwitterionic or negative TAs by cationic Al (III) species drove removal of TAs from the synthetic water. When sufficient alkalinity was available (river water), aluminum hydroxide precipitates were formed. TAs could be removed by being enmeshed into or adsorbed onto the precipitates when PACl was added to the river water.     

Optimization of coag-flocculation processes of a newly synthesized quaternized oil palm empty fruit bunch cellulose by response surface methodology toward drinking water treatment process application

An optimization of coagulation and flocculation of kaolin suspension by a newly synthesized quaternized oil palm empty fruit bunch cellulose denoted as a 9QC was investigated using the central composite design of the response surface methodology. The influences of coag-flocculant dosage, pH, and kaolin suspension on turbidity removal efficiency and sludge volume index responses were studied and assessed according to a 2³ full factorial design. The developed quadratic models revealed that the overall optimum values to obtain the highest performance of the responses were 62.5 mg/L of coag-flocculant dosage, pH 7, and 1400 mg/L of kaolin concentration. The predicted optimum responses were found to be in close proximity to the observed responses. The coag-flocculating of river water using 9QC carried out at the optimum values showed encouraging results as compared to alum which is commonly used in drinking water treatment process.     

A quantitative comparison between electrocoagulation and chemical coagulation for boron removal from boron-containing solution

This paper provides a quantitative comparison of electrocoagulation and chemical coagulation approaches based on boron removal. Electrocoagulation process delivers the coagulant in situ as the sacrificial anode corrodes, due to a fixed current density, while the simultaneous evolution of hydrogen at the cathode allows for pollutant removal by flotation. By comparison, conventional chemical coagulation typically adds a salt of the coagulant, with settling providing the primary pollutant removal path. Chemical coagulation was carried out via jar tests using aluminum chloride. Comparison was done with the same amount of coagulant between electrocoagulation and chemical coagulation processes. Boron removal obtained was higher with electrocoagulation process. In addition, it was seen that chemical coagulation has any effect for boron removal from boron-containing solution. At optimum conditions (e.g. pH 8.0 and aluminum dose of 7.45 g/L), boron removal efficiencies for electrocoagulation and chemical coagulation were 94.0% and 24.0%, respectively.     

Coagulation–flocculation process with metal salts,synthetic polymers and biopolymers for the removal of trace metals (Cu,Pb, Ni,Zn) from municipal wastewater

To ensure compliance with regulatory standards, it is important to examine the potential of treatment technologies to enhance trace metal removal from wastewater. This study investigated the effectiveness of coagulation–flocculation at removing trace metals from humus effluent with ferric chloride (FeCl₃), the synthetic polymer polyethyleneimine (PEI) and the biopolymers chitosan and floculan. Effluent samples were collected from a trickling filter treatment works operating in the UK and contained 21 ± 4 μg/L Cu, 0.8 ± 0.1 μg/L Pb, 4 ± 1 μg/L Ni and 43 ± 9 μg/L Zn. The influence of coagulant dosage and the velocity and time of the slow mixing stage were studied via a series of jar tests. Chitosan and PEI had a moderate effect on the removal of trace metals (≤ 35%). FeCl₃ removed 48% Cu, 56% Pb and 41% Zn at the optimised dose of 0.10 mg/L. At the optimised dose of 0.25 mg/L, floculan removed 77% Cu, 68% Pb and 42% Zn. The dominant mechanism for particle removal by FeCl₃ was enmeshment in the precipitates (i.e. sweep flocculation), whereas, for floculan, inter-particle bridging was the dominant removal mechanism. Overall, FeCl₃ and floculan were found to be most effective at removing trace metals from wastewater.