Chemical and physical treatments of chemical mechanical polishing wastewater from semiconductor fabrication

Wastewater from chemical mechanical polishing (CMP) process of semiconductor fabrication was treated by physical methods. The CMP wastewater, as obtained from a large semiconductor manufacturer, was characterized by a high oxide particle content, high turbidity (NTU), and a chemical oxygen demand (COD) concentration up to 500 mg/l. Due to these characteristics, treatment of the CMP wastewater by either filtration or by traditional activated sludge method was inadequate. In the present work, physical methods consisting of chemical coagulation and reverse osmosis were employed to tackle the turbidity and COD problems. Experimental tests were conducted to assess the effectiveness of the treatment and to identify the optimum operating conditions. Test results clearly demonstrated the complementary advantages of the two methods. The treatment was capable of realizing over 99% oxide particle removal and lowering the wastewater COD to below 100 mg/l. The overall water quality of the final effluent was excellent and can be considered for reuse. Preliminary treatment of the RO retentate by ozonation was also attempted. The COD removal achieved in the ozonation was over 80% in an hour, rendering the treated RO retentate suitable for direct discharge.     

Enhancement of bioseparation and dewaterability of domestic wastewater sludge by fungal treated dewatered sludge

A promising biological, sustainable, non-hazardous, safe and environmental friendly management and disposal technique of domestic wastewater sludge is global expectation. Fungal entrapped biosolids as a result of prior fungal treated raw wastewater sludge was recycled to evaluate its performance as inoculum for bioseparation/bioconversion of supplemented sludge in view of continuous as well as scale up wastewater sludge treatment. Encouraging results were achieved in bioseparation of suspended solids and in dewaterability/filterability of treated domestic wastewater sludge. Fungal entrapped biosolids offered 98% removal of total suspended solids (TSS) in supplemented sludge treatment at 6-day without nutrient (wheat flour, WF) supply. Consequently, 99% removal of turbidity and 87% removal of chemical oxygen demand (COD) were achieved in supernatant of treated sludge. The lowest value (1.75 x 10(12)m/kg) of specific resistance to filtration (SRF) was observed at 6-day after treatment, which was equivalent to the 70% decrease of SRF. The all results except SRF were not influenced further in treatments accompanied with WF supplementation. The present treatments offered significant (P相似文献   

Three dimensional woven fabrics as filter media in membrane bioreactor for wastewater treatment

Filters used in membrane bioreactors (MBRs) for wastewater treatment are low in filtration efficiency and the filtration process using MBR is relatively expensive, when low turbidity of treated water is required. To improve the filtration efficiency, three dimensional (3D) orthogonal woven fabrics with textured weft yarns are developed as a filter media used in MBR. Compared with a regular high-density two dimensional fabric filter, the 3D filter with multilayer and tortuous porous structure allows for 1–3 times higher flux and two times more filtered amount of wastewater in 30 days, while still maintaining a stable effluence turbidity and COD removal efficiency. The potential of applying the novel 3D woven filter in MBR for efficient wastewater treatment is proved.     

Optimization of electrochemical treatment of industrial paint wastewater with response surface methodology

The electrochemical oxidation of water-based paint wastewater was investigated batch-wise in the presence of NaCl electrolyte with carbon electrodes for the first time in literature. The electrochemical treatment conditions were optimized using response surface methodology where potential difference, reaction temperature and electrolyte concentration were to be minimized while chemical oxygen demand (COD), color and turbidity removal percents and initial COD removal rate were maximized at 100% pollution load. The optimum conditions were satisfied at 35 g/L external electrolyte concentration, 30 degrees C reaction temperature and 8 V potential difference (64.37 mA/cm(2) current density) realizing 51.8% COD and complete color and turbidity removals, and 3010.74 mg/Lh initial COD removal rate. According to these results, the electrochemical method could be a strong alterative to conventional physicochemical methods for the treatment of water-based paint wastewater.     

Electrochemical treatment of deproteinated whey wastewater and optimization of treatment conditions with response surface methodology

Electrochemical treatment of deproteinated whey wastewater produced during cheese manufacture was studied as an alternative treatment method for the first time in literature. Through the preliminary batch runs, appropriate electrode material was determined as iron due to high removal efficiency of chemical oxygen demand (COD), and turbidity. The electrochemical treatment conditions were optimized through response surface methodology (RSM), where applied voltage was kept in the range, electrolyte concentration was minimized, waste concentration and COD removal percent were maximized at 25 degrees C. Optimum conditions at 25 degrees C were estimated through RSM as 11.29 V applied voltage, 100% waste concentration (containing 40 g/L lactose) and 19.87 g/L electrolyte concentration to achieve 29.27% COD removal. However, highest COD removal through the set of runs was found as 53.32% within 8h. These results reveal the applicability of electrochemical treatment to the deproteinated whey wastewater as an alternative advanced wastewater treatment method.     

可反洗平板膜生物反应器处理园区生活污水研究

就可反洗平板浸没式膜生物反应器和传统平板浸没式膜生物反应器处理园区生活污水的效果进行比较研究,发现在水力停留时间同为9.6h的条件下,两者几无区别,COD和NH3-N的去除率同样分别为90%和95%,浊度均降至0.7NTU以下,也均无SS检出,出水水质都达到国家生活杂用水水质标准(GB/T18920-2002);但前者因膜具可反洗性,可以延缓膜污染,延长系统稳定运行周期,减少化学清洗频率,既降低运行成本,延长膜使用寿命,又减少化学清洗剂对环境的污染.     

超滤膜生物反应器处理生活污水的试验研究

用外压一体化中空纤维超滤膜生物反应器（ＵＭＢＲ）进行了处理生活污水的试验．结果表明,当水力停留时间（ＨＲＴ）为５ｈ、膜通量在４４２～１１０Ｌ／ｈ时,ＵＭＢＲ对生活污水中ＣＯＤ、浊度、ＳＳ的去除率分别可达９０％、９８％、１００％,出水ＣＯＤ＜６０ｍｇ／Ｌ、浊度＜３、ＳＳ为０,污泥质量浓度ρＭＬＳＳ、污泥负荷Ｆｒ、反应器容积负荷ＦＷ分别为６２ｋｇ／ｍ３、０４６ｋｇ／（ｋｇ·ｄ）、１８２ｋｇ／（ｍ３·ｄ）．初步探讨了超滤膜的堵塞机理,通过杀菌清洗可使超滤膜通透能力恢复到新膜的９７％以上．ＵＭＢＲ出水浊度低,水质稳定,宜于回用     

Hybrid processes for the treatment of cattle-slaughterhouse wastewater using aluminum and iron electrodes

Electrocoagulation (EC) of cattle-slaughterhouse wastewater, which is characterized by (i) high turbidity (up to 340 Nephelometric turbidity units), (ii) increased chemical oxygen demand (COD) concentration (4200 mg L(-1)), and (iii) a dark color, was investigated with the purpose of lowering the turbidity and COD concentration to levels below the permitted direct-discharge limits. Iron and aluminum were used as electrode materials. Experiments were conducted to evaluate the effects of current density, initial pH, and supporting electrolyte (Na(2)SO(4)) dosage on the performance of the system. COD removal increased with increase in current density. The original pH of wastewater (7.8) was found to be preferable for both the electrode materials. Higher concentrations of Na(2)SO(4) caused an increase in COD removal efficiency, and energy consumption was considerably reduced with increasing conductivity. Hybrid processes were applied in this work to achieve higher COD removal efficiencies. In the case of aluminum electrode, polyaluminum chloride (PAC) was used as the coagulant aid for the aforesaid purpose. COD removal of 94.4% was obtained by adding 0.75 g L(-1) PAC. This removal efficiency corresponded to effluent COD concentration of 237 mg L(-1), which meets the legal requirement for discharge from slaughterhouses in Turkey. In the case of iron electrode, EC was conducted concurrent with the Fenton process. As a result, 81.1% COD removal was achieved by adding 9% H(2)O(2). Consequently, hybrid processes are inferred to be superior to EC alone for the removal of both COD and turbidity from cattle-slaughterhouse wastewater.     

HEAVY METALS REMOVAL IN A RAPID INFILTRATION SAND COLUMN

Sand filtration has been used as a cost-effective tertiary treatment process for sewage and wastewaters. However, little information is available on the performance of the process for heavy metals removal. In this project, the effect of a rapid infiltration sand filtration system on the removal of total organic carbon (TOC) phosphorus, Cd, Cu, Pb, and Zn from a mixed industrial and domestic wastewater was evaluated. To facilitate observation of the system behavior under varied conditions, the influent samples were also subjected to extreme pH values. Further studies were conducted to determine the effects of calcium carbonate addition for heavy metals precipitation prior to application onto the sand column. The results revealed that sand filtration was remarkably successful in removing phosphorus from wastewater under all conditions. The data further confirmed that in a sand filtration process, the mechanism of phosphorus removal was mainly due to chemical precipitation. Under neutral pH conditions, TOC, Cd, and Cu, were removed in the order of 20%, and Pb, and Zn were about 35-40% removed. Addition of a chemical precipitant such as calcium carbonate increased the pollutant removal to about 50%. At pH values below 2.4 and above 11.0, the TOC and all the metals showed an increase in concentration in passing through the sand column.     

HEAVY METALS REMOVAL IN A RAPID INFILTRATION SAND COLUMN

ABSTRACT

Sand filtration has been used as a cost-effective tertiary treatment process for sewage and wastewaters. However, little information is available on the performance of the process for heavy metals removal. In this project, the effect of a rapid infiltration sand filtration system on the removal of total organic carbon (TOC) phosphorus, Cd, Cu, Pb, and Zn from a mixed industrial and domestic wastewater was evaluated. To facilitate observation of the system behavior under varied conditions, the influent samples were also subjected to extreme pH values. Further studies were conducted to determine the effects of calcium carbonate addition for heavy metals precipitation prior to application onto the sand column. The results revealed that sand filtration was remarkably successful in removing phosphorus from wastewater under all conditions. The data further confirmed that in a sand filtration process, the mechanism of phosphorus removal was mainly due to chemical precipitation. Under neutral pH conditions, TOC, Cd, and Cu, were removed in the order of 20%, and Pb, and Zn were about 35–40% removed. Addition of a chemical precipitant such as calcium carbonate increased the pollutant removal to about 50%. At pH values below 2.4 and above 11.0, the TOC and all the metals showed an increase in concentration in passing through the sand column.     

Confirming Pseudomonas putida as a reliable bioassay for demonstrating biocompatibility enhancement by solar photo-oxidative processes of a biorecalcitrant effluent

The performance of a sequencing batch reactor (SBR) seeded with aerobic granular sludge was studied. The lab-scale SBR treating domestic wastewater operated at a volumetric loading rate (VLR) of 0.75-3.41 kg COD/(m(3)d). The granule stability was related to the organic loading, and high loading would be favorable for granule stability. Analysis of typical cycle showed that granular sludge had good ability to simultaneously remove nitrogen and phosphorus. Most organic substances were removed at the anaerobic stage. At the aerobic stage, simultaneous nitrification and denitrification (SND) happened with phosphorus absorption. The SBR had good removal performance for organic matter and phosphate. However, the total nitrogen (TN) removal performance was ordinary, with average removal efficiency of about 52%. Batch experiments indicated that increases of influent C/N ratio and a large percentage of granule in the sludge were conducive for SND in SBR.     

Electrochemical treatment of simulated textile wastewater with industrial components and Levafix Blue CA reactive dye: optimization through response surface methodology

The electrochemical oxidation of simulated textile wastewater was studied on iron electrodes in the presence of NaCl electrolyte in a batch electrochemical reactor. The simulated textile wastewater was prepared from industrial components based on the real mercerized and non-mercerized cotton and viscon process, being first in literature. The highest COD, color and turbidity removals were achieved as 93.9%, 99.5%, and 82.9%, respectively, at 40% pollution load, 8 V applied potential, 37.5 g/L electrolyte concentration and 30 degrees C reaction temperature. The electrochemical treatment of industrial textile wastewater was optimized using response surface methodology (RSM), where applied potential and electrolyte concentration were to be minimized while COD, color and turbidity removal percents were maximized at 100% pollution load. In a specific batch run under the optimum conditions of 30 degrees C reaction temperature, 25 g/L electrolyte concentration and 8 V applied potential applied with 35.5 mA/cm2 current density at 100% pollution load, COD, color and turbidity removals were realized as 61.6%, 99.6% and 66.4%, respectively.     

Innovative physico-chemical treatment of wastewater incorporating Moringa oleifera seed coagulant

Moringa oleifera is a pan tropical, multipurpose tree whose seeds contain a high quality edible oil (up to 40% by weight) and water soluble proteins that act as effective coagulants for water and wastewater treatment. The use of this natural coagulant material has not yet realised its potential. A water extract of M. oleifera seed was applied to a wastewater treatment sequence comprising coagulation-flocculation-sedimentation-sand filtration. The study was laboratory based using an actual wastewater. Overall COD removals of 50% were achieved at both 50 and 100mg/l M. oleifera doses. When 50 and 100mg/l seed doses were applied in combination with 10mg/l of alum, COD removal increased to 58 and 64%, respectively. The majority of COD removal occurred during the filtration process. In the tests incorporating alum, sludge generation and filter head loss increased by factors of 3 and 2, respectively. These encouraging treatment results indicate that this may be the first treatment application that can move to large scale adoption. The simple water extract may be obtained at minimal cost from the presscake residue remaining after oil extraction from the seed. The regulatory compliance issues of adopting 'new materials' for wastewater treatment are significantly less stringent than those applying to the production of potable water.     

Removal of organic pollutants from 2,2',5,5'-tetrachlorobenzidine (TCB) industrial wastewater by micro-electrochemical oxidation and air-stripping

A feasible method for treatment of the wastewater from the two-staged neutralization in 2,2',5,5'-tetrachlorobenzidine (TCB) manufacturing processes, a refractory dye intermediate effluents, based on combined micro-electrochemical oxidation or iron-chipping filtration (ICF) and air-stripping reactor (ASR), was developed. On conditions of HRT 1h, pH 3.0 in ICF and HRT 38 h, gas-liquid ratio 15, pH 6.0-8.65, temperature 26 degrees C in ASR, the overall COD, color, TCB and NH(4)(+)-N removal were 96.8%, 91%, 87.61% and 62%, respectively, during the treatment of TCB wastewater from the two-staged neutralization dissolved by methanol. The averaged 18.3%, 81.7% of the total degraded COD, 35.2%, 64.8% of TCB were carried out in ICF and ASR, respectively. NH(4)(+)-N removal was finished mainly in ASR. The experimental results indicated that the combined micro-electrochemical oxidation and air-stripping process performed good treatment of COD, color, TCB and NH(4)(+)-N removal in TCB wastewater from the two-staged neutralization dissolved by ethanol or acetone, came up the discharge standard in China. But the TCB wastewater from the two-staged neutralization dissolved by methanol should be deeply treated before discharged.     

Characterization and treatability studies of tannery wastewater using chemically enhanced primary treatment (CEPT)--a case study of Saddiq Leather Works

Chemically enhanced primary treatment (CEPT) is a technology that uses coagulants for enhanced pollutants removal at the primary stage of the wastewater treatment. This paper presents the detailed characteristics of tannery wastewater. It also explains effectiveness of CEPT in removing pollutants from tannery wastewater using various metal salts. The results of this study demonstrated that the tannery effluent had high concentrations of organic matter, solids, sulfates, sulfides and chromium. Alum, ferric chloride and ferric sulfate were tested as coagulants using jar test apparatus. Alum was found to be the suitable coagulant for tannery wastewater in a dose range of 200-240 mg/L as Al(2)(SO(4))(3). With alum, percentage removal efficiency for turbidity, total suspended solids (TSS), chemical oxygen demand (COD) and chromium was found to be 98.7-99.8, 94.3-97.1, 53.3-60.9, and 98.9-99.7%, respectively. National effluent quality standards for total suspended solids and chromium were met after CEPT. However, COD content was high, emphasizing the need of secondary treatment for the tannery effluent.     

Treatment of organophosphate-contaminated wastewater by acidic hydrolysis and precipitation

Wastewater from commercial manufacture of organophosphate (OP) pesticide of O-methyl-O-(2-isopropyl salicylate) thiophosphorusyl amide contains large amounts of organophosphate, organic sulfides, COD and NH3-N. A treatment process including acidic hydrolysis and precipitation was explored in this paper. The effects of initial pH values, hydrolysis temperature and hydrolysis time on the removal of pollutants were investigated. The experimental results showed that, in the hydrolysis, with the decreasing initial pH value, the removal of OP, sulfide and COD rose whereas the NH3-N removal declined. Increased hydrolysis temperature and time favored the removal of all the pollutants. 15.0 wt% Ca(OH)2 was sufficient for the removal of inorganic phosphorus and residual NH3-N in the precipitation step. With this chemical process, the removal of total phosphorus (TP), organophosphate, sulfides and NH3-N exceeded 90%, and the removal of COD was about 60%. The BOD5/COD value was greatly improved from 0.05 to 0.3, and the bio-degradability of the wastewater was greatly improved. The NH3 generated in the process was absorbed with water and might be reused in the manufacture of the pesticide. The results showed that this comprehensive process is effective for the treatment of this typical unbio-degradable pesticide wastewater.     

Treatment of the baker's yeast wastewater by electrocoagulation

In the laboratory-scale experiments, treatment of baker's yeast production wastewater has been investigated by electrocoagulation (EC) using a batch reactor. Effects of the process variables such as pH, electrode material (Fe and Al), current density, and operating time are investigated in terms of removal efficiencies of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and operating cost, respectively. The maximum removal efficiencies of COD, TOC and turbidity under optimal operating conditions, i.e., pH 6.5 for Al electrode and pH 7 for Fe electrode, current density of 70 A/m2 and operating time of 50 min were 71, 53 and 90% for Al electrode and 69, 52 and 56% for Fe electrode, respectively. Al electrode gave 4.4 times higher removal efficiency of turbidity than Fe electrode due to interference from color of dissolved iron. The operating costs for Al and Fe electrodes in terms of $/m3 or $/kg COD were 1.54 and 0.82, 0.51 and 0.27, respectively.     

CMF系统处理生活污水厂二级出水

研究了连续微滤技术(CMF)在深度处理城市污水厂二级排放水中的应用前景,以某污水厂SBR(sequenting batch reactor)工艺二级出水为原水,着重考虑了CMF系统对水中OoD、SS、浊度等指标的去除效果,试验结果表明:CMF系统对水中COD有30%左右的去除率,出水浊度低于0.5 NTU.采用扫描电镜及能谱分析对膜污染物分析,得知膜表面的污染物以微生物和有机物为主.     

Electrolytic treatment of Standard Malaysian Rubber process wastewater

A new method of Standard Malaysian Rubber (SMR) process wastewater treatment was developed based on in situ hypochlorous acid generation. The hypochlorous acid was generated in an undivided electrolytic cell consisting of two sets of graphite as anode and stainless sheets as cathode. The generated hypochlorous acid served as an oxidizing agent to destroy the organic matter present in the SMR wastewater. For an influent COD concentration of 2960 mg/L at an initial pH 4.5+/-0.1, current density 74.5 mA/cm(2), sodium chloride content 3% and electrolysis period of 75 min, resulted in the following residual values pH 7.5, COD 87 mg/L, BOD(5) 60 mg/L, TOC 65 mg/L, total chlorine 146 mg/L, turbidity 7 NTU and temperature 48 degrees C, respectively. In the case of 2% sodium chloride as an electrolyte for the above said operating condition resulted in the following values namely: pH 7.2, COD 165 mg/L, BOD(5) 105 mg/L, TOC 120 mg/L, total chlorine 120 mg/L, turbidity 27 NTU and temperature 53 degrees C, respectively. The energy requirement were found to be 30 and 46 Wh/L, while treating 24 L of SMR wastewater at 2 and 3% sodium chloride concentration at a current density 74.5 mA/cm(2). The observed energy difference was due to the improved conductivity at high sodium chloride content.     

Influence of hydraulic loading and air flowrate on urban wastewater nitrogen removal with a submerged fixed-film reactor

Nutrient disposal to sensitive areas, particularly nitrogen and phosphorus from wastewater treatment plants, provokes eutrophication reducing water quality. Fixed film technology is widely used for the removal of organic matter and nitrogen by the biological process of nitrification-denitrification. This paper studies a nitrification and post-denitrification lab-scale plant with a downflow aerobic submerged filter for removal of organic matter and nitrification, followed by an anoxic upflow biofilter for denitrification. Recycled construction material (clay shists) was employed as support material and methanol was used as carbon source. After 2 weeks of acclimation in which nitrification reached steady-state conditions, different hydraulic loadings (0.35-1.59 m(3)/m(2)h) and air flowrates (7.78-43.5 m(3)/m(2)h) were applied for 1 year. The highest hydraulic loading which complied with the EU regulation on nitrogen disposal was 0.71 m(3)/m(2)h (1.6 h). Hydraulic retention time (HRT), which corresponded to a nitrogen removal of 0.64 kg N/m(3) per day operating at an air flowrate of 25.6 m(3)/m(2)h. Concerning to organic matter removal efficiency, the aerobic reactor accepted a maximum chemical oxygen demand (COD) volumetric loading of 16.0 kg COD/m(3) per day with a 75% COD removal efficiency. For all the tests carried out, suspended solids (SS) concentration in the outlet water was less than 35 mg/l.