Turbidity Removal Rate Research Articles

Synthesis and evaluation of a novel cationic konjac glucomannan-based flocculant

A novel cationic flocculant of konjac glucomannan-graft-poly-(2-methacryloyloxyethyl)trimethyl ammonium chloride (KGM-g-PDMC), was successfully synthesized by using acidic ammonium cerium (IV) nitrate (CAN) as initiator in homogeneous aqueous solution. The graft copolymer was characterized using Fourier-transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA) and elemental analysis. The influences of degree of substitution (DS) of KGM, concentration of NaCl and pH value on turbidity removal rate of the cationic flocculant were investigated. The results demonstrated that the flocculant exhibited excellent flocculating ability in the presence of salt and a wide range of pH (1<pH<9). With DS of 0.2, the turbidity removal rate of flocculant to 0.1% kaolin suspension could reach more than 90% at pH 7.0. The flocculation mechanisms were investigated by screening effect and means of zeta potential. Holding the positive charge, the KGM-g-PDMC could efficiently remove the negatively charged contaminants such as kaolin suspension.

Performance assessment of modified biosand filter with an extra disinfection layer

Biosand filters (BSFs) have been used widely as an efficient, inexpensive, and appropriate point-of-use technology. Several organizations are promoting filters without adequate testing, which may not lead to sufficiently safe devices. The objective of this study was to evaluate the performance of a modified biosand filter (MBSF) with an extra disinfection layer (brass or zero valent iron (ZVI)) and three layers of underdrain in a range of parameters including Escherichia coli , total coliform, turbidity, pH, and dissolved oxygen. On average, a 91.29% reduction (log 1.43) in total coliform, 98.7% reduction (log 2.6) in E. coli and 88.71% reduction in turbidity were observed for the control. There was a 90.11% reduction (log 1.41) in total coliform, 98.2% reduction (log 2.25) in E. coli , and 88.5% reduction in turbidity for MBSF brass. A 96.93% reduction (log 1.81) in total coliform, 97.33% reduction (log 2.36) in E. coli and 91.5% reduction in turbidity for MBSF ZVI were observed. Adding brass as a disinfection layer in MBSF did not improve bacteria and turbidity removal rates. Adding ZVI as a disinfection layer gave better turbidity and total coliform removal relative to control and MBSF brass. Water quality remained within drinking water standards for all filters.

Research on an emergency treatment technology for black-odor water caused by macrophytes decaying

水草腐烂加速水体耗氧和水体还原性物质的溶出进程,在夏、秋季高温条件下极易引发局部水体黑臭.以太湖沉水植物优势种马来眼子菜(Potamogeton malaianus)、苦草(Vallisneria natans)及浮叶植物优势种莕菜(Nymphoides peltatum)为受试材料,利用太湖原位底泥培养模拟水草腐烂形成的黑臭水体,考察不同的环境材料处置方式(壳聚糖(CTS)、聚合氯化铝(PAC)、聚丙烯酰胺(PAM)、CTS+PAC和PAC+PAM)对黑臭水体浊度、溶解氧浓度、挥发性硫化物等黑臭水体特征污染物的絮凝沉降规律及去除机理.结果表明:(1)絮凝处理24 h后,CTS+PAC组合对黑臭水体的浊度去除效果最佳,浊度去除率达70.3%,上覆水溶解氧浓度明显提高,增加率为261.5%;(2)加石英砂悬浊液加速絮体沉淀,形成絮体之后加石英砂使水体浊度稳步下降,4 h之后,浊度去除率达74.9%,显著高于与絮凝剂一起加入的处理组(29.8%);(3)植物腐烂释放的含硫特征嗅味物质主要为硫化氢(H₂S)、甲硫醚和二甲基三硫醚.不同植物体腐烂释放的含硫挥发性有机物浓度差异显著,马来眼子菜释放的4种含硫有机物总和分别为莕菜和苦草释放的319.8%和252.2%;(4)CTS+PAC处理后苦草及马来眼子菜腐烂水体中挥发性有机硫化物浓度较对照组分别降低了18.6%和44.5%.PAC+PAM组合絮凝处理组对莕菜腐烂水体中H₂S有较好的去除效果,去除率达到52.4%.CTS+PAC絮凝剂组合处理的H₂S浓度均低于对照组,苦草、马来眼子菜和莕菜腐烂后黑臭水体中H₂S浓度分别降低了27.4%、41.0%和28.6%.CTS+PAC组合对H₂S和二甲基硫醚类物质等致臭物释放的抑制效果优于PAC+PAM组合絮凝处理.;Aquatic plants decaying will accelerate the process of dissolved oxygen depletion and promote the dissolution of reducing substance, which can easily lead to partial water black-odor in a hot summer. In this study, dominant species of submerged plants Potamogeton malaianus, Vallisneria natans and floating-leaved dominant species Nymphoides peltatum in Lake Taihu were selected as test material. Then the macrophytes decayed in cylindrical sediment in the culture system in which simulated conditions in situ. The black-odor waters were formed to study the flocculation and sedimentation kinetics, removal mechanism of water turbidity, volatile sulfide, dissolved oxygen and other water and soil interface characteristics which were treated with different environmental material disposals(chitosan(CTS), poly aluminum chloride(PAC), polyacrylamide(PAM), CTS+PAC and PAC+PAM). The results suggest that:(1) After 24 h, the turbidity removal of black smelly water treated by CTS+PAC was optimal, when turbidity removal rate was 70.3%. The CTS+PAC combination can increase the dissolved oxygen in overlying water more significantly than other environmental material disposals, and the increase rate is 261.5%.(2) Taking flocculation experiments by joining flocculants in the black smelly water with different flocculants, the suspension of quartz sand was added at different timing. Quartz sand suspension can accelerate flocculant precipitation, adding quartz sand before flocculant is significantly better than after it with turbidity removal rate 74.9% compared to 29.8%.(3) Sulfur characteristic odor compounds released by decay aquatic plants are mainly hydrogen sulfide(H₂S), dimethyl sulfide and dimethyl trisulfide. volatile organic sulfur compounds(VOSCs) released by difference decayed plants was significantly different. The sum of the four forms of organic sulfur released from Potamogeton malaianus were 319.8% of Nymphoides peltatum and 252.2% of biter grass.(4) Volatile organic sulfur compounds contents of Vallisneria natans and Potamogeton malaianus decaying water treated by CTS+PAC was reduced by 18.6% and 44.5%. Treatment PAC+PAM has a good deodorizing effect on Nymphoides peltatum for the removal rate of H₂S reached 52.4% when treatment CTS+PAC affected both three kind of plants. The content of H₂S reduced by 27.4%, 41.0% and 28.6% in Vallisneria natans, Potamogeton malaianus and Nymphoides peltatum, respectively. The inhibitory effect of odorant(such as H₂S and dimethyl sulfide) in treatment CTS+PAC was higher than that in treatment PAC+PAM.

Treatment of Preserved Wastewater with UASB

The preserved wastewater was treated by the upflow anaerobic sludge blanket (UASB) reactor, the effects of the anaerobic time on COD, turbidity, pH, conductivity, SS, absorbance, and decolorization rate of the preserved wastewater were investigated. The results showed that with the increase of the anaerobic time, the treatment effect of the UASB reactor on the preserved wastewater was improved. Under the optimum anaerobic time condition, the COD removal rate, turbidity removal rate, pH, conductivity, SS removal rate, absorbance, and decoloration rate of the wastewater were 49.6%, 38.5%, 5.68, 0.518×10 4 , 24%, 0.598, and 32.4%, respectively. Therefore, the UASB reactor can be used as a pretreatment for the preserved wastewater, in order to reduce the difficulty of subsequent aerobic treatment.

Decontamination Features and Mechanism Research of Copolymerization Dissolved Air Flotation Process

In the traditional dissolved air flotation (DAF), micro bubbles generally cannot mesh and adhere to particles efficiently, and the adhesion between microbubbles and particles is not stable, either. In this paper, a self-developed copolymerization dissolved air flotation (Co-DAF) system was proposed to strengthen the copolymerization of condensation reaction during the adhesion of bubbles and flocs, by grading the refluxed dissolved air water, which could significantly enhance the adhesion efficiency and the stability of the bubble-flocs. On this basis, raw water of low turbidity, high algae and high organic contents from the Yellow River reservoir was used as the water supply to verify the effectiveness of the proposed system. The results showed that the average removal rate of turbidity was 95.2%, among, which 93.6% of the particles larger than 2 μm were removed effectively. Meanwhile, the removal rates of CODMn, UV254, DOC, SUVA and ammonia nitrogen were 43.2%, 48.5%, 38.2%, 20.5 and 77.3%, respectively, and those of organics with molecular weight between 3000–10000 Da and more than 3000 Da were 30.6% and 85%, respectively. However, for those organics with molecular weight less than 1000 Da, only a removal rate of 10% was achieved. During the test, DBPFP could be well controlled by the Co-DAF process, and the removal rates of CHCl 3, CHClBr2, CHCl 2Br and CHBr3 were 22.9%, 21.9%, 16.0% and 18.2%, respectively. It was deduced that the mechanisms of removing pollutants by the Co-DAF process mainly included the collision and adhesion effects between micro bubbles-floc particles, the copolymerization between microbubble-flocs and particles, and the adsorption bridging effects among bubble-flocs, microbubbles and particles.

Optimization of magnetic-seeding coagulation in artificially polluted surface water treatment by response surface methodology

Artificially polluted surface water was treated using magnetic-seeding coagulation, with polyaluminum chloride (PAC) as the coagulant and a ferromagnetic material as the magnetic seed (MS). A novel approach using a combination of response surface methodology (RSM) and the Box–Behnken design (BBD) was employed to evaluate the effects and interactions of four main factors, the dosages and dosing points of PAC and MS. The three response variables selected to evaluate the effectiveness of the treatment were supernatant turbidity removal rate, floc size, and floc strength. The optimal operating conditions were obtained by constraining the three desirable responses using Minitab software. The PAC and MS dosages (22.7 mg/L and 0.6 g/L) and their dosing points (1.5 and 1.2 min) were determined to be the optimum conditions for the maximum turbidity removal rate, floc size, and floc strength of 98.0%, 154.7 μm, and 57.8%, respectively. Confirmation experiments demonstrated that such a combination of RSM and BBD was a powerful and effective approach for optimizing the magnetic-seeding coagulation. Additionally, zeta potential analysis indicated that the MS decreases the negative charge of pollutants and acts as a coagulating core during coagulation.

Performance of an Integrated Treatment System for Clean Drinking Water Production

This study is related to the removal of organics and other pollutants from drinking water using an integrated treatment system consisting of coagulation–sedimentation, ozonation and granular activated carbon (GAC)‐enhanced sand filtration. Standard methods and instruments were employed to measure turbidity, chemical oxygen demand determined by using the permanganate method as permanganate index (CODMn), UV254, total organic carbon (TOC), ammonia and nitrite of raw and treated water under controlled laboratorial conditions. The experimental results demonstrated that the total removal rates of turbidity, CODMn, UV254 and TOC were in the range of 98–99.9, 21–71, 33–73 and 20–47%, respectively, in different units of the integrated treatment system. GAC‐enhanced sand filtration significantly removed ammonia and nitrite, and the average removal efficiency was attained to 88 and 98%, respectively. In addition, most of the organic matter concentrations were observed to be reduced in GAC‐enhanced sand filtration and only small molecular weight compounds were detected in the effluent. All these pollutant reductions were noticed in the upper 350 mm of the activated carbon column in GAC‐enhanced sand filtration. The findings from this study suggest that the integrated treatment process can efficiently remove organics and other toxic pollutants from drinking water and can be a better alternative to conventional treatment.

Development of activated carbon auto-regeneration system for water treatment filtration

Activated carbon facilities for water treatment should be regenerated or changed because their adsorption capacities decrease with the passage of operating time. A novel system of activated carbon auto-regeneration system for water treatment filtration (ARWF), which has been recently developed, is capable of both operations of adsorption treatment and activated carbon regeneration simultaneously. Upon the adsorption, capacity of activated carbon has decreased to a certain level, the process of regeneration starts automatically. Regenerating process is operated by boiler, line heater, and spray which are located at nozzle pipe inside column. The process uses a super-heated steam of which temperature is 400–600°C. Steam of 100–110°C is generated by steam boiler and then super-heated steam of 400–600°C is created by line heater. Super-heated steam is sprayed with activated carbon through spray nozzle pipe. A series of experiments were performed to evaluate the ARWF on the capacity of regeneration. The result showed that the ARWF was able to regenerate a used activated carbon almost same (98%) as a new carbon in terms of iodine adsorption. The values of iodine adsorption for original and 10 times regenerated carbons were 1,074 and 1,046 mg/g, respectively. In the removal of COD and BOD, the removal rate of new activated carbon was 80%, which was 5–10% higher than that of the first and second regenerated ones. The chromaticity and turbidity removal rate was higher in the regenerated carbon than in the new carbon.

Simultaneous Removal of Turbidity and Humic Acid Using Electrocoagulation/Flotation Process in Aqua Solution

In this study, the applicability of the Electrocoagulation/Flotation (ECF) process in batch operation was investigated for the simultaneous removal of turbidity and Humic acid (HA) using Fe and Al electrodes. The effects of solution pH (3 - 12), electrical potentials (10 - 30 V), initial turbidity concentration (300 - 1200 NTU), and reaction time (10 - 30 minutes) with or without HA were investigated in an attempt to achieve higher turbidity removal efficiency. The batch experimental results revealed that with initial turbidity of 300 NTU, at voltage of 30 V, after 30 minutes reaction times, and at pH values of 6 and 8, the ECF process for Fe and Al electrodes removed over 97% and 88% of turbidity, respectively. The percentage of turbidity removal from solution dropped with a decrease in voltages for both electrodes. The results displayed that the Fe-Fe electrode arrangement attained the highest performance for turbidity removal rate. As a result, ECF process was shown to be a very efficient, cost-effective, and promising process for efficient treatment of high turbid water. Regarding HA, the results showed that in ECF process over 67% and 43% of UV254 has been removed for Al and Fe electrodes, respectively at the optimum pH, 30 minutes reaction time and 30 V applied voltage. Thus, it can be considered that Fe and Al are the best electrodes for removing turbidity and HA, respectively.

Characterization and coagulation–flocculation behavior of an inorganic polymer coagulant – poly-ferric-zinc-sulfate

Recent studies on improving the behavior of the coagulation–flocculation process have attracted a widespread interest. Iron-based composite coagulant has been demonstrated to enhance the performance of the coagulation–flocculation in previous research. In this research, a type of coagulant, poly-ferric-zinc-sulfate (PFZS) was prepared by co-polymerization. The preparation process was optimized by using response surface method (RSM). The structure and morphology of PFZS were investigated by FTIR, XRD and SEM. In addition, parameters affecting coagulation–flocculation behavior such as coagulant dosage, initial pH in wastewater and settling time were also studied. The results show that the optimum temperature, Zn/Fe molar ratios and aging time for preparation of PFZS are 70 °C, 1.0 and 3.0 h, respectively; FTIR and XRD results demonstrate that PFZS is a complex compound with mainly ferric-zinc polymeric species rather than a simple mixture of raw materials. In the coagulation–flocculation process of municipal sewage treatment, PFZS exhibits a better coagulation performance compared with poly-ferric-sulfate (PFS). At optimal pH value in the range of 7–9, PFZS can reach the best turbidity removal rate 93.42% at a dosage of 12 mg/L, whereas PFS can only reach 90.36% at the best coagulant dosage of 16 mg/L.

Polymeric flocculant based on cassava starch grafted polydiallyldimethylammonium chloride: Flocculation behavior and mechanism

In this work, flocculation properties of cassava starch grafted polydiallyldimethylammonium chloride (polyDADMAC) with different grafting percentages were investigated. Flocculation performance was evaluated in simulated kaolin suspension. The grafting percentages used were 1.76 %, 14.84 %, and 21.98 %. The effectiveness of the flocculation was measured based on the reduction of the turbidity and total suspended solids (TSSs), zeta potential measurements, particle size, and atomic force microscopy imaging. Grafted polymers improved the removal rate of turbidity and TSS compared with gelatinized starch, and the removal rate increased with increasing grafting percentage and dosage.

Characterization and flocculation mechanism of a bioflocculant from potato starch wastewater.

This study investigated the characterization and flocculation mechanism of a bioflocculant prepared using potato starch wastewater. The optimal culture conditions of this strain were determined as 4 g K2HPO4, 2 g KH2PO4, 0.2 g MgSO4, 0.1 g NaCl, and 2.0 g urea dissolved in 1.0 L potato starch wastewater with no need of adding carbon sources or adjusting pH value. Production of this bioflocculant was positively associated with cell growth, and a highest value of 0.81 g/L was obtained. During the kaolin suspension flocculation, charge neutralization and interparticle bridging were proposed as the main reasons for enhanced performance. Further, with potato starch wastewater, chemical oxygen demand (COD) and turbidity removal rates reached 52.4 and 81.7 %, respectively, at pH 7.5 when the bioflocculant dose was adjusted to 30 mg/L.

Development of a hybrid treatment system for combined sewer overflows using a hydrocyclone and a dissolved air flotation system

Combined sewer overflows (CSOs) contain a mixture of untreated, contaminated sanitary, and storm water. CSOs include both precipitated and suspended matters. In this study, a novel system is proposed to treat CSOs using a combined hydrocyclone and dissolved air flotation (DAF) system for removal of both precipitated and suspended matter. The optimum operating conditions were determined by changing the internal flow rate and the split ratio (Rf) in the hydrocyclone and by changing the angle of the nozzle to determine the floc size, flow rate, and recycle ratio in the DAF system. The types of organic matter contained in prepared synthetic water samples are categorized as soluble CODcr (SCOD) and particulated CODcr (PCOD) in the characterization of the removal rate of the precipitated and suspended matter. The suspended solids (SS) were classified by their specific gravity to determine the removal rate of both precipitated and suspended matter. In a pretreatment process, the system employed a cationic polymer to obtain a low gradient time (G × t) value. The results showed that poly-aluminum chloride (PAC) used with the cationic polymer had a 9.2% higher turbidity removal rate than PAC alone, due to a stable floc being achieved in the hydrocyclone. The optimum operating conditions of the hydrocyclone showed the highest efficiency at Rf = 10% at a flow rate of 2.8 m/s; the DAF-treated solutions showed a higher removal rate for SCOD solutions vs. PCOD solutions, with the highest turbidity removal rate of 65%. In contrast, when the hydrocyclone-treated solutions had a higher PCOD than SCOD, they showed a higher removal efficiency. The removal rates of SS, CODcr, turbidity, T-P, and T-N of the total process were 77, 80, 98, 98, and 45%, respectively.

Characterization of a bioflocculant from potato starch wastewater and its application in sludge dewatering.

A bioflocculant was produced by using potato starch wastewater; its potential in sludge dewatering and potato starch wastewater treatment was investigated. Production of this bioflocculant was positively associated with cell growth, and a highest value of 0.81 g/L was obtained. When incubated with this bioflocculant, dry solids (DS) and specific resistance to filtration (SRF) of typical wastewater activated sludge reached 20.8% and 3.9 × 10(12) m/kg, respectively, which were much better than the ones obtained with conventional chemical flocculants. Sludge dewatering was further improved when both the bioflocculant and conventional polyacrylamide (PAM) were used simultaneously. With potato starch wastewater, chemical oxygen demand (COD) and turbidity removal rates could reach 52.4 and 81.7%, respectively, at pH value of 7.5 when the bioflocculant dose was adjusted to 30 mg/L; from a practical standpoint, the removal of COD and turbidity reached 48.3 and 72.5%, respectively, without pH value adjustment.

How Does a Group of Iranian Youth Conceptualize Their Risky Sexual Experiences?

Chitosan, a biodegradable polymer, is used as an eco-friendly coagulant in a wide variety of applications in water and wastewater treatment. The present study aimed to investigate the effect of chitosan as a coagulant aid combined with poly aluminum chloride (PAC) to enhance coagulating efficiency for bentonite suspensions. A conventional jar test apparatus was used for the tests. The effect of various operational parameters, such as initial pH of the solution (5-9.5), dosage of chitosan (0.5-3.5 mg/L), dosage of PAC (5-35 mg/L) and initial turbidity (50-200 NTU) were investigated. The maximum turbidity removal rates were obtained as pH 8.5 for PAC and pH 7.5 for combined PAC and chitosan (CPC). The coagulating efficiency of bentonite using PAC and CPA was found to decrease with an increase in the pH value of the solutions. The maximum turbidity removal rate was achieved in coagulating by PAC (30 mg/L) alone, and PAC (20 mg/L) combined with chitosan (2.5 mg/L) as coagulant aid with the removal rate of 87% and 96%, respectively. The optimum dosage of chitosan required to obtain the highest removal rate was 2.5 mg/L. Hence, using chitosan as a coagulant aid can not only reduce the required amount of coagulant (35%) but can also enhance the removal turbidity efficiency.

Toxicological assessment and management options for boat pressure-washing wastewater

Boats are washed periodically for maintenance in order to remove biofoulants from hulls, which results in the generation of wastewater. This study aimed at evaluating the cyto/genotoxic and mutagenic properties of wastewater produced by pressure washing of boats. The chemical characterisation of this wastewater showed that Cu, Zn, V, Cr, Fe, Pb, and select organic contaminants exceeded the maximum allowable values from 1.7 up to 96 times. The wastewater produced negative effects on human lymphocytes resulting in decreased cell viability after 4 and 24h of exposure. Chromosome aberration, micronucleus, and comet assay parameters were significantly higher after 24h of exposure. At the same time, the Salmonella typhimurium test showed negative for both TA98 and TA100 strains at all of the concentrations tested. After the treatment of wastewater using electrochemical methods/ozonation during real scale treatment plant, removal rates of colour, turbidity and heavy metals ranged from 99.4% to 99.9%, while the removal of total organic carbon (TOC) and chemical oxygen demand (COD) was above 85%. This was reflected in the removal of the wastewater's cyto/genotoxicity, which was comparable to negative controls in all of the conducted tests, suggesting that such plants could be implemented in marinas to minimise human impact on marine systems.

High Efficiency Phosphorus Flocculants Prepared with Red Mud for Treating Lake Water

In this study, different acid modification methods were used to prepare two types of inorganic flocculation compounds. First, under simulated wastewater conditions, the optimal input quantity for phosphorus elimination of flocculant #1 was 0.5 g/L, and the optimal agitation conditions were rapid agitation at 300 rpm for 60 s followed by slow agitation at 20 rpm for 15 min. The optimal input amount of flocculant #2 was 0.8 g/L, and the optimal agitation conditions were rapid agitation at 300 rpm for 30 s followed by slow agitation at 100 rpm for 10 min. Then they were used to treat water from the East Lake. The removal rates of TP, ammonia nitrogen, COD, and turbidity by flocculant #1 were 91.45%, 60.90%, 80.71%, and 93.05%, respectively; the corresponding removal rates by flocculant #2 were 92.74%, 58.49%, 76.92%, and 84.66%, respectively. The discharged water for both flocculants had TP and COD concentrations that met the type III standards in GB3838-2002.

Characterization and Application Process Optimization of CuO/γ-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3 &lt;/sub&gt;Catalyst in CWAO Technology

CuO/γ-Al2O3 catalyst was used to deal with the waste leachate in CWAO technology of, and the SEM and TEM characterization showed: active component in the surface of the carrier distribution is uniform; In CWAO process, six factors, based on the CODCr removal rate and turbidity removal rate, the biggest impact factor is reaction temperature, and the influence factors of the top three were reaction temperature, catalyst dosage and reaction time. The influence factors of those in the bottom three are influent water pH, oxygen partial pressure, stirring intensity, and three factors of influence on the strength is close. Optimizing operation process, in order: reaction temperature of 200 °C, catalyst dosage of 1.5 g, oxygen partial pressure of 2.0 MPa, stirring intensity 800 rpm, influent water pH of 7.0, the reaction time of 70 min.

Comparison on Permanganate and Ozone as Pre-Oxidation Agents

Comparative study on permanganate and ozone as pre-oxidation agents were performed on pilot scale with traditional drinking water treatment process, chemical oxygen demand (COD), total organic carbon (TOC), UV254, turbidity, trihalomethane formation potential (THMFP) were examined at each reactor’s effluent. The results show that at pre-oxidation reactor, the total organic remained stable after by the two agents, while for UV254, pre-ozonation has a removal rate of 34%, comparing that of 17% by permanganate. At the sedimentation process, 0.4 mg/L permanganate improves the removal rate of turbidity and COD by 0.99 % and 8.4%, respectively; while a positive COD removal of 11.8 % was achieved by 0.9 mg/L pre-ozonation, and an average of-10.08% turbidity removal was achieved at applied dosage (0.5, 0,9 and 1.5 mg/L), which can be made up for in the followed sand filtration reactor. Both permanganate and pre-ozonation show higher removal rate of THMFP for the finished water.

Performance study of ZrO2 ceramic micro-filtration membranes used in pretreatment of DMF wastewater

Three kinds of 19-channel ZrO2 micro-filtration membranes with different pore size were used for pretreatment of dimethylformamide (DMF) wastewater from the polyurethane (PU) synthetic leather factories, which would enter the distillation column for further purification. The effects of membrane pore size, cross flow velocity (CFV) and transmembrane pressure (TMP) on ceramic membrane filtration performances were investigated. Experimental results indicated that the optimum membrane pore size, CFV and TMP were 0.2μm, 3m·s−1 and 0.2MPa, respectively, with the corresponding liquid turbidity removal rate of 99.62% and suspended solid content retention rate of 99.99%. The membrane fouling mechanism was analyzed by resistance in series model. The main resistance derived from the particle adsorption and sedimentation on the membrane surface. The ratio of particle adsorption and sedimentation resistance to total resistance was above 70% for the 0.2μm membrane. The backflushing technology was applied and the effect of backflushing on the permeate flux was studied. The permeate flux eventually increased by 50% with the optimum backflushing pressure of 0.6MPa, backflushing time of 5s and backflushing interval of 20min. A combination cleaning method was used to regenerate the ZrO2 micro-filtration membrane. The pure water flux recovered to 608.2L·m−2·h−1 and flux recovery rate was 96.8% which indicated that the combination cleaning method was effective.