超滤用于海水淡化预处理的研究进展

良好的预处理是保证反渗透(RO)装置长期稳定运行的关键要素之一.与传统预处理技术相比,UF预处理能够有效降低海水的SDI、浊度和TOC等,为RO装置提供优良、稳定的进水,增强RO膜的可靠性.详细评述了近年来国内外采用UF技术作为RO淡化预处理过程的研究和应用进展.此外,对UF膜的污染和控制对策研究进展也作了评述.UF作为膜法海水预处理技术已成为该领域的发展趋势.     

Integrating an anaerobic Bio-nest and an aerobic EMMC process as pretreatment of dairy wastewater for reuse: a pilot plant study

A large dairy farm located on the island of Oahu, Hawaii was the site for an investigation for the potential integration of the existing facultative lagoon system with a cost effective pretreatment unit process. Based on the results from a laboratory study, a pilot plant was installed with two anaerobic bioreactors (10 m3 each) and one aerobic reactor (3.8 m3). Two layers of media “Bio-nest,” providing a void volume of 98%, were placed into each anaerobic bioreactor with 19% space-based on the bioreactor water volume. For better performance and reduction of shock-load, the equalization/settling tank was employed prior to the first anaerobic Bio-nest reactor. The intermediate holding tank settled effluent suspended solids from the Bio-nest reactor and adjusted the loading rate in order to improve the performance of the aerobic EMMC (entrapped mixed microbial cell) bioreactors. Based on the start-up operation of the Bio-nest system at an organic loading rate of about 1.5 g TCOD/l/day, the production rate of biogas from the first and second Bio-nest reactors was 0.64 and 0.15 l/l/day, respectively. This indicates that the anaerobic degradation of organics occurs mainly in the first Bio-nest reactor due to the low loading rate. The removal efficiency from the Bio-nest system shows TCOD removal of about 70%. The EMMC process provided further treatment to achieve a removal efficiency of TCOD at about 50% and a TN of about 35%. The cost for these pretreatments in order to be integrated with the existing lagoon system is US $1.1 per 1,000 gallons (3.8 m3) for dairy wastewater and $1.1 per 1,000 gallons (3.8 m3) for dairy wastewater and 91 for each ton of TCOD removal. This integration system provides a sustainable improvement of environment and agricultural production.     

Stripping as a pretreatment process of industrial oily wastewater

In the present work, the potential of purifying an oily wastewater from a lubricant production unit, consisting mainly of alcohols, phenols and heavy linear saturated hydrocarbons, using the stripping process was examined. The effect of stripping gas flow (75-300 L(N2) L(WW)(-1) h(-1)) and system temperature (295-355 K) on the chemical oxygen demand (COD) of the effluent was investigated. A decrease in COD content of 25-30% was achieved after 4 h for stripping gas flow rates over 150 L(N2)L(WW)(-1) h(-1), whereas the rate of organic compounds removal was enhanced by increasing temperature up to 333 K. At higher temperatures an effluent condensation was observed. Gas chromatography-mass spectrometry analysis of both liquid and gas phase showed that linear saturated hydrocarbons of high molecular weight were stripped out from the wastewater. The results are in agreement with the equilibrium ratio of these compounds as predicted from by theoretical calculations.     

采用纳滤预处理的海水淡化集成技术

海水淡化是解决淡水危机的主要方法之一，但由于海水的硬度、浊度和总固溶物含量均非常高，因而导致淡化水的能耗量和成本较高．采用纳滤膜技术可以降低海水的硬度和总固溶物及有机物的含量，减少结垢与污染，提高水回收率，有望实现海水淡化成本的进一步降低．详细介绍了纳滤与常规蒸馏法、膜法海水淡化相结合而构成的新型纳滤预处理海水淡化集成技术：NF—MSF、NF—SWRO、NF—SWROrej-MSF等的国外研究与应用进展情况．     

Biodegradability enhancement of purified terephthalic acid wastewater by coagulation-flocculation process as pretreatment

In this work, the coagulation-flocculation process was used as pretreatment for purified terephthalic acid (PTA) wastewater with the objective of improving its overall biodegradability. PTA production generates wastewaters with toxicants p-xylene [1,4-dimethyl-benzene (C8H10)], a major raw material used in the production process, along with some of the intermediates, viz., p-toluic acid, benzoic acid, 4-carboxybenzaldehyde, phthalic acid and terephthalic acid. These compounds affect the bio-oxidation process of wastewater treatment; hence removal of these constituents is necessary, prior to conventional aerobic treatment. This paper addresses the application of coagulation-flocculation process using chemical coagulants, viz., aluminium sulphate (alum), polyaluminium chloride (PAC), ferrous sulphate and ferric chloride in combination with anionic polyelectrolyte. Polyaluminium chloride (PAC) in conjunction with lime and polyelectrolyte removed about 63.1% chemical oxygen demand (COD) and 45.2% biochemical oxygen demand (BOD) from PTA wastewater. Coagulation-flocculation process coupled with aerobic bio-oxidation treatment of PTA wastewater achieved, COD & BOD removals of 97.4% and 99.4%, respectively. The biodegradability enhancement evaluated in terms of the BOD5/COD ratio, increased from 0.45 to 0.67 at the optimum conditions. The results obtained from these studies indicate that the coagulation-flocculation process could be a suitable pretreatment method in reducing toxicity of PTA wastewater whilst enhancing biodegradability for aerobic biological treatment scheme.     

Electrochemical oxidation of textile wastewater and its reuse

It is attempted in the present investigation to treat organic pollutant present in the textile effluent using an electrochemical treatment technique. Experiments are carried out in a batch electrochemical cell covering wide range in operating conditions. Due to the strong oxidizing potential of the chemicals produced, the effluent COD is reduced substantially in this treatment technique. The influence of effluent initial concentration, pH, supporting electrolyte concentration and the anode material on pollutant degradation has been critically examined. It is further attempted in the present investigation to reuse the treated wastewater for dyeing purpose. Several cycles of dyeing operations have been performed with the treated textile wastewater and the dye uptake and water quality have been critically examined at each cycle of dyeing process. The results indicate that the electrochemical method is a feasible technique for treatment of textile wastewater and electrochemically treated wastewater can be effectively reused for dyeing application.     

Eco-friendly process for soft drink industries wastewater reuse as growth medium for Saccharomyces cerevisiae production

Soft drink industries suffer inadequate handling of their product losses generally considered as wastes. Those products contribute to the wastewater organic load augmentation and cause fastidious environmental impact. In this study, an industrial scale bioconversion process based on multistage fermentation was proposed to treat and reuse soft drink factories’ high-loaded effluents for valuable components production. An upstream segregation of non-consumed beverage was performed to reduce the organic load of the soft drink wastewater. Beverage characterization revealed an important sugar content. Such an organic compound is undoubtedly responsible of the high organic load of soft drink wastewater. Thus, the bioconversion of the sugar content of soft drink waste to single-cell proteins was proposed as a solution to reduce wastewater polluting load. Soft drink wastewater including rejected and returned products was tested to be used as a substrate for yeast biomass production using a commercial yeast strain of Saccharomyces cerevisiae. The effect of nutrient supplementation and the initial sugar concentration effect in culture media on the biomass production were investigated using batch and fed-batch process. Results indicated that supplementation is necessary for successful fermentation. Juices and nectars gave better sugar-biomass conversion yields (0.38–0.45 g g⁻¹). Depletion of the sugar contained in the soft drinks exceeded 96 % for all fermented media. Fed-batch culture revealed a biomass concentration improvement reaching 9.16 g L⁻¹ compared to batch biomass concentration resulting from batch cultures (5.2 g L⁻¹). The proposed process was shown to enable beverage industries to reduce water pollution generation through an on-site segregation procedure and a storage system to valorize product losses as source medium for single-cell protein production.

     

环渤海地区膜法海水淡化预处理工艺探讨

海水淡化是环渤海地区经济发展的重大课题.海水预处理是淡化的关键过程.文章结合渤海湾地区海水水质的特点,讨论了膜法海水淡化预处理工艺的选择,设计时对水温,浊度变化的考虑.对连续膜过滤工艺的类型和特点作了介绍.     

用集成膜过程对含油废水进行资源化回收利用处理

采用电渗析与超滤、微滤相结合的集成膜过程对含油废水进行了资源化回收利用处理,并对该工艺中电渗析脱盐过程的各项运行参数与分离效果之间的关系进行了讨论.在此基础上,为进一步改善出水水质,还对不同材料的超滤、微滤膜去除废水CODCr的效果作了相应的实验比较.     

Biological treatment and nanofiltration of denim textile wastewater for reuse

This study aims at coupling of activated sludge treatment with nanofiltration to improve denim textile wastewater quality to reuse criteria. In the activated sludge reactor, the COD removal efficiency was quite high as it was 91+/-2% and 84+/-4% on the basis of total and soluble feed COD, respectively. The color removal efficiency was 75+/-10%, and around 50-70% of removed color was adsorbed on biomass or precipitated within the reactor. The high conductivity of the wastewater, as high as 8 mS/cm, did not adversely affect system performance. Although biological treatment is quite efficient, the wastewater does not meet the reuse criteria. Hence, further treatment to improve treated water quality was investigated using nanofiltration. Dead-end microfiltration (MF) with 5 microm pore size was applied to remove coarse particles before nanofiltration. The color rejection of nanofiltration was almost complete and permeate color was always lower than 10 Pt-Co. Similarly, quite high rejections were observed for COD (80-100%). Permeate conductivity was between 1.98 and 2.67 mS/cm (65% conductivity rejection). Wastewater fluxes were between 31 and 37 L/m2/h at 5.07 bars corresponding to around 45% flux declines compared to clean water fluxes. In conclusion, for denim textile wastewaters nanofiltration after biological treatment can be applied to meet reuse criteria.     

膜生物反应器在污水处理与回用中的能耗分析

介绍了膜生物反应器(MBR)低能耗化研究进展,以吨水能耗(kWh/m3)和COD去除能耗(kWh/kgCOD)两种指标分析比较了MBR处理较低浓度城镇和生活污水、较高浓度工业废水及垃圾渗滤液等废水的运行能耗与成本,分析了MBR运行能耗构成和能耗较高的原因,并对MBR节能措施和对策进行了讨论.     

Hydrolytic pretreatment of oily wastewater by immobilized lipase

The purpose of this study was to evaluate the hydrolysis of wastewater with high oil and grease (O&G) concentration from a pet food industry using immobilized lipase (IL) as a pretreatment step for anaerobic treatment through batch and continuous-flow experiments. The intrinsic Michaelis constant (K(m)) and maximum reaction rate (V(max)) were estimated experimentally and the K(m) value of IL (22.5g O&G/L) was six-folds higher than that of the free lipase (FL) (3.6gO&G/L), whereas V(max) of both FL (31.3mM/gmin) and IL (33.1mM/gmin) were similar. Preliminary batch anaerobic respirometric experiments showed that chemical oxygen demand (COD) and O&G reduction were 49 and 45% without pretreatment and 65 and 64% with IL pretreatment respectively, while the maximum growth rate (micromax) for pretreated wastewater (0.17d(-1)) was 3.4-folds higher than that of raw wastewater (0.05d(-1)) with similar Monod half-saturation constants (K(s) approximately 2.7gCOD/L). The continuous-flow experimental study showed the feasibility of employing the hybrid packed bed reactor (PBR)-upflow anaerobic sludge blanket (UASB) system for the treatment of high-strength oily wastewater, as reflected by its ability to operate at an oil loading rate (LR) of 4.9kgO&G/m(3)d (to the PBR) without any problems for a period of 100days. During pseudo-steady-state conditions, the hybrid UASB produced relatively higher biogas compared to the control UASB, The effluent COD and O&G concentrations of hybrid system were 100mg/L lower than that of the control UASB reactor and no foam production was observed in the hybrid UASB compared to the control UASB reactor.     

Simultaneous methane production and wastewater reuse by a membrane-based process: evaluation with raw domestic wastewater

In this study, a membrane-based process was applied to simultaneously reclaim methane and generate reused water from raw domestic wastewater. The system was comprised of up-flow anaerobic sludge fixed bed (UAFB), anoxic sink (AS) and aerobic membrane bioreactor (MBR). The hydraulic retention time of UAFB (HRT(U)) was gradually shortened from 8h to 6h, 3h and to 1h, while the HRT of AS and MBR kept at 8 h. It is found that HRT(U) of 3h was more suitable for the balancing production of biogas and volatile fatty acids (VFAs), and the VFAs served as carbon source for denitrification. The trans-membrane pressure (TMP) of the MBR kept lower than 0.04 MPa without wash or change of membrane sheet, however, the scanning electron microscopy (SEM) analysis indicated that microbes attached to the inner-surface of membrane, causing irreversible fouling after 133-day operation. The denaturing gradient gel electrophoresis (DGGE) profiles of amplified 16S rDNA gene fragments proved that more functional bacteria and higher microbial diversity emerged at HRT(U) of 3h and 1h. Most bacteria belonged to Betaproteobacteria and were responsible for carbon and nitrogen removal.     

膜生物反应器用于城市污水处理与回用的试验研究

采用规模为40m^3／d的膜生物反应器对城市污水处理回用进行了试验研究．试验结果表明：膜生物反应器具有较强的抗冲击负荷能力，活性污泥对污染物的去除起主要作用，膜分离对维持稳定的出水起重要作用．膜生物反应器出水稳定，水质良好，优于生活杂用水水质标准(CJ25．1—89)．     

Evaluation of biodegradability and oxidation degree of hospital wastewater using photo-Fenton process as the pretreatment method

In this work, the photo-Fenton process was used for the pretreatment of hospital wastewater with the objective of improving its overall biodegradability and determining the degree of increased oxidation. The chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), total organic carbon (TOC) and toxicity towards the gram negative marine bioluminescent bacteria of the species V. fischeri were selected as the environmental sum parameters to follow the performance of this process. The enhancement of biodegradability, evaluated in terms of the BOD5/COD ratio, increased from 0.3 to 0.52 and the oxidation degree, calculated in terms of AOS, leveled up from -1.14 to +1.58 at the optimum conditions; a dosage ratio of COD:H2O2:Fe(II) at 1:4:0.1, and a reaction pH of 3. The reduction in the inhibition percentage from the toxicity test indicated the safe levels for micro-organisms in degrading the residual organic substance in this method. Almost total removal percentages of COD, BOD5, and TOC were found by a sequential activated sludge process for the pre-treated wastewater. Results obtained from this work indicated that the photo-Fenton process could be a suitable pretreatment method in reducing toxicity of pollutants and enhancing biodegradability of hospital wastewaters treated in a coupled photochemical-biological system.     

反渗透技术在钢厂特大型废水回用项目中的应用

针对山西某大型钢厂不锈钢股份有限公司工业废水成份非常复杂、含盐量高和处理难度大等特点,以及国家对钢铁企业节能减排的号召,确定了以反渗透技术为主的脱盐工艺来回用该厂的工业废水,有效降低该厂吨钢的新水消耗量.运行结果表明,反渗透系统的脱盐效果非常好,给钢厂带来了很好的水质保障.本文详述了时代沃顿反渗透膜在钢铁厂废水回用系统中的应用情况.