Production integrated treatment of textile wastewater by closing raw material cycles.

A method for the in-house treatment of partial wastewater flows and the recycling of treated process water into the textile finishing process was developed in order to recycle effluents from textile finishing industry and feed them back into the production process. The method is based on a two-stage biological anaerobic-aerobic process to split colouring wastewater agents and to degrade organic substances contained in the water as well as a chemical stage to remove the remaining color of the water with the help of ozone. In the framework of a research and development project a demonstration plant for a treatment capacity of 1440 m3 per working day was installed and started in a textile finishing company. At the plant, a wastewater flow and a recycling flow are treated separately in two different treatment lanes. Approximately 40% of the total wastewater flows, i.e. 576 m3/d are treated in the wastewater lane, and a maximum of 60% of total wastewater, i.e. 864 m3/d are treated in the recycling lane. Thanks to the preliminary treatment of wastewater flows, which are discharged into the municipal sewage works, a reduction of average COD levels in the sewage works effluents could be achieved.     

Membrane bio-reactor for advanced textile wastewater treatment and reuse.

Textile wastewater contains slowly- or non-biodegradable organic substances whose removal or transformation calls for advanced tertiary treatments downstream Activated Sludge Treatment Plants (ASTP). This work is focused on the treatment of textile industry wastewater using Membrane Bio-reactor (MBR) technology. An experimental activity was carried out at the Baciacavallo Wastewater Treatment Plant (WWTP) (Prato, Italy) to verify the efficiency of a pilot-scale MBR for the treatment of municipal wastewater, in which textile industry wastewater predominates. In the Baciacavallo WWTP the biological section is followed by a coagulation-flocculation treatment and ozonation. During the 5 months experimental period, the pilot-scale MBR proved to be very effective for wastewater reclamation. On average, removal efficiency of the pilot plant (93% for COD, 96% for ammonium and 99% for total suspended solids) was higher than the WWTP ones. Color was removed as in the WWTP. Anionic surf actants removal of pilot plant and WWTP were very similar (92.5 and 93.3% respectively), while the non-ionic surfactants removal was higher in the pilot plant (99.2 vs. 97.1). In conclusion the MBR technology demonstrated to be effective for textile wastewater reclamation, leading both to an improvement of pollutants removal and to a draw-plate simplification.     

Performance of membrane bioreactors used for the treatment of wastewater from the chemical and textile industries.

Within the scope of the study, nine waste waters from the chemical and textile industries were treated in bench-scale (laboratory scale) and small-scale (pilot scale) membrane bioreactors. Depending on wastewater characteristics, the resulting performance varied significantly. It was observed that MBR effectiveness was determined primarily by the degree of biodegradability of the wastewater. In the course of several months of operation, no significant changes associated with the complete retention of the biomass by the membranes were observed. In some cases, it was possible to improve effluent quality by using smaller molecular separation sizes. The flux performance of the membrane modules was dependent on wastewater composition. Occasionally, non-degradable macromolecular substances concentrated in the bioreactor, resulting in strongly reduced filterability and flow performance of the membrane modules, consequently also reducing the economic viability of the process. The results demonstrate that wastewater-specific pilot tests are absolutely necessary, in particular if the technology is to be used for new applications.     

Membrane filtration and sonication for industrial wastewater reuse

This paper presents an experimental study aimed at estimating the efficiency of the innovative process of ultrafiltration (UF) combined with sonication (Son.) for the refinement of treated effluent to be reused in wet textile processes. Such a novel approach, which has not yet been employed on a full industrial scale, has been experienced at pilot scale on the secondary effluent of the Baciacavallo wastewater treatment plant (WWTP), which treats part of the effluent from one of the largest textile industry districts in Italy. The combined treatment efficiency was assessed both on ozonated and non-ozonated Baciacavallo secondary effluent. The membrane filtration process was optimized in terms of running time, backwash, chemical addition and cleaning procedures. The sonication treatment was optimized on laboratory-scale with synthetic solutions (demineralized water added with dyestuffs) in terms of hydroxyl radicals formation rate, frequency, acoustic power, hydrogen peroxide addition, contact time and pH. The optimal conditions have been applied on the pilot-scale sonicator which was used in combination with the UF treatment. According to the experimental results, the best configuration within the Baciacavallo WWTP was the sonication of non-ozonated wastewater followed by the UF. The combined treatment guaranteed the compliance with the target values for wastewater reuse in wet textile industries. This study is part of the Research Project PURIFAST (Purification of industrial and mixed wastewater by combined membrane filtration and sonochemical technologies) LIFE + ENV/IT/000439.     

Enhanced biological wastewater treatment using sodium alginate-immobilized microorganisms in a fluidized bed reactor

In this study, a microbial consortium isolated from an activated sludge tank of a conventional wastewater treatment plant was immobilized using sodium alginate (SA) as a support material for contaminant biodegradation in wastewater. A volume of 500 mL of activated sludge was immobilized in the SA beads (with a mass concentration of 25 g/L). The resulting SA beads were characterized, introduced into a fluidized bed reactor, fed with 1000 mL of the sample, and characterized again after the treatment process. The SA-immobilized microorganisms were tested first for degradation of organic matter (expressed as chemical oxygen demand) and total phosphorous in domestic wastewater, achieving removal efficiencies of 71% and 93%, respectively, after 12 h. Subsequently, the SA-immobilized microorganisms were tested for degradation of a basic blue 9 (BB9) textile dye in a condition that simulated textile wastewater. The efficiency of the BB9 degradation was found to be as high as 99.5% after 2 h. According to these results, SA-immobilized microorganisms were found to be an environmentally friendly and cost-effective alternative for treatment of municipal and industrial wastewater effluents.     

Reuse of industrial wastewater for the irrigation of ornamental plants.

This paper describes the results of experimental activities carried out for verifying the possibility of reusing reclaimed wastewater originated from textile (70%) and domestic (30%) activities for the irrigation of container-grown ornamental shrubs. Aspects that concern the refinery treatment of reclaimed wastewater and the effect of irrigation on some ornamental plant species were investigated. An experimental site consisting of a refinery treatment pilot plant (filtration and disinfection) and an agronomic experimental area was set-up. The combined treatment of PAA and UV, used for the disinfection, showed to be very effective for inactivation of E. coli with most of PAA and UV dose combinations able to assure total inactivation. The plants (Buxus, Photinia, Pistacia and Viburnum), sprinkle and drip irrigated with well water (WW), reclaimed wastewater (RW) and a water mixed (MW) between reclaimed wastewater and well water (1:1 by vol), showed interesting results. A similar growth among different treatments was achieved for Buxus and Pistacia, while Viburnum and Photinia plants showed a higher sensibility to MW and RW. Photinia, in particular, turned out to be very sensitive to sprinkle irrigation with the reclaimed water, while the drip irrigation had no such bad effects, as reported in previous works.     

Pumped flow biofilm reactors (PFBR) for treating municipal wastewater

A novel laboratory bench-scale sequencing batch biofilm reactor (SBBR) system was developed for the treatment of synthetic domestic strength wastewater, comprising two side-by-side 18 l reactor tanks, each containing a plastic biofilm media module. Aerobic and anoxic conditions in the biofilms were effected by intermittent alternate pumping of wastewater between the two reactors. With a media surface area loading rate of 4.2 g chemical oxygen demand (COD)/m2.d, the average influent COD, total nitrogen (TN) and ammonium-nitrogen (NH4-N) concentrations of 1021 mg/l, 97 mg/l and 54 mg/l, respectively, reduced to average effluent concentrations of 72 mg COD/l, 17.8 mg TN/l, and 5.5 mg NH4-N /l. Using a similar alternating biofilm exposure arrangement, a 16 person equivalent pilot (PE) plant was constructed at a local village treatment works to remove organic carbon from highly variable settled municipal wastewater and comprised two reactors, one positioned above the other, each containing a module of cross-flow plastic media with a surface area of 100 m2. Two different pumping sequences (PS) in the aerobic phase were examined where the average influent COD concentrations were 220 and 237 mg/l for PS1 and PS2, respectively, and the final average effluent COD was consistently less than 125 mg/l--the European Urban Wastewater Treatment Directive limit--with the best performance occurring in PS1. Nitrification was evident during both PS1 and PS2 studies. A 300 PE package treatment plant was designed based on the bench-scale and pilot-scale studies, located at a local wastewater treatment works and treated municipal influent with average COD, suspended solids (SS) and TN concentrations of 295, 183 and 15 mg/l, respectively resulting in average effluent concentrations of 67 mg COD/l, 17 mg SS/l and 9 mg TN/l. The SBBR systems performed well, and were simple to construct and operate.     

太阳能曝气人工垂直潜流湿地去除生活污水氮磷的试验研究

利用芦苇和砾石构建太阳能曝气人工垂直潜流湿地处理生活污水。设定水力负荷400 mm/d,气水比10∶1,当进水氨氮(NH₄-N)、总氮(TN)、溶解性反应磷(SRP)和总磷(TP)平均浓度为5.14,7.56,0.40,0.53 mg/L时,引入太阳能曝气后,各自的平均去除率分别提高24.8%,9.4%,15.7%和11.5%。随着气温下降和进水浓度降低,湿地微生物脱氮除磷能力下降,曝气对改善生活污水氮磷去除作用不显著。对试验系统而言,太阳能曝气湿地基本建设费用是无曝气湿地的2.85倍;但以20 a运行为基础折算出的污水处理费比无曝气湿地仅高0.02元/m³。综上,从污染去除性能和污水长期处理费用来看,太阳能曝气湿地在生活污水处理方面具有较好的技术经济优势。     

微量营养物质对毛纺废水生物处理效果的影响

研究了Mg、Mo、Zn、维生素B1以及烟酸等微量营养物质对活性污泥降解CODCr活性的 影响,同时,对微量营养物质作用前后处理系统微生物群落结构进行了比较研究。试验结果表明:毛 纺废水缺乏生物处理系统所需足够的微量营养物质;不同种类和浓度的微量营养物质对活性污泥降 解CODCr活性的影响效果也不相同,Mg、Mo、Zn、雏生素B1和烟酸的最佳浓度分别为5 mg／L, 2 mg／L,1 mg／L,1 mg／L和1 mg／L;其最佳促进效果可使CODCr降解速率分别达到对照系统的 180％、140％、130％,160％和220％。添加微量营养物质显著改变了微生物群落结构。     

Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.     

Electron beam treatment of textile dyeing wastewater: operation of pilot plant and industrial plant construction.

A pilot plant for treating 1000 m3/day of dyeing wastewater with e-beam has been constructed and operated since 1998 in Daegu, Korea together with the biological treatment facility. The wastewater from various stages of the existing purification process has been treated with an electron beam in this plant, and it gave rise to elaborating the optimal technology of the electron beam treatment of wastewater with increased reliability for instant changes in the composition of wastewater. Installation of the e-beam pilot plant resulted in decolorizing and destructive oxidation of organic impurities in wastewater, appreciable reduction of chemical reagent consumption, in reduction of the treatment time, and in increase in the flow rate limit of existing facilities by 30-40%. Industrial plant for treating 10,000 m3/day each, based upon the pilot experimental result, is under construction and will be finished by 2005. This project is supported by the International Atomic Energy Agency (IAEA) and Korean Government.     

Application of anaerobic biological treatment for sulphate removal in viscose industry wastewater.

Long term lab-scale and bench-scale experiments were performed to investigate the feasibility of the anaerobic process to treat wastewater from a pulp and viscose fibre industry. Anaerobic wastewater treatment enables an advantageous combination of COD, sulphate and zinc removal from viscose wastewater. The aim of the investigations was to evaluate the influence of the free sulphide concentration on COD and sulphate removal efficiency and on the substrate competition between sulphate reducing and methanogenic bacteria. Since the wastewater did not contain enough COD for complete sulphate removal it was of major interest to determine favourable process conditions to steer the substrate competition in favour of sulphate reduction. Further experiments at bench-scale permitted us to evaluate applicable COD-loading rates and gain fundamental information about process stability and optimization for large-scale implementation. The present work will deal with the most relevant experimental results achieved and with important technological aspects of anaerobic treatment of viscose wastewater.     

MBR fouling control and permeate quality enhancement by polyaluminium chloride dosage: a case study

Scope of this study was to evaluate the effectiveness of a metal salt (polyaluminium chloride, PACl) dosage into a pilot-scale MBR (membrane bioreactor) in terms of fouling control and permeate quality enhancement, especially with reference to specific textile macro-pollutants (dyes and surfactants). The pilot plant was fed with a mixed domestic-textile wastewater (textile wastewater accounted for 65% of total flow and for 70% of total chemical oxygen demand, COD, load) and operated for 7.5 months without flux enhancers (step 1) and 3 months with the addition of PACl (step 2). The optimum dose was defined performing a jar-test campaign between step 1 and step 2 (12.5 mg gMLSS(-1) that corresponds to 0.4 g d(-1)). The addition of PACl resulted in a significant decrease of the filtration resistance due to cake layer formation (R(c), -65.4%) and of the irreversible fouling rate, evaluated as the average variation per unit time of the filtration resistance due to foulants adsorption on membrane pore wall (FR, -45.3%). As for permeate quality, removal rates related to total phosphorus and textile macro-parameters such as colour and anionic surfactants, increased by +64, +16 and +7%, respectively. No significant effect was observed on COD, non-ionic surfactants and nitrogen compounds removal.     

Control of C/N ratio for butyric acid production from textile wastewater sludge by anaerobic digestion

Increasing textile wastewaters and their biotreatment byproduct-waste activated sludge are serious pollution problems. Butyric acid production from textile wastewater sludge by anaerobic digestion at different C/N ratios was investigated. Adding starch to textile wastewater sludge with a C/N ratio of 30 increased the butyric acid concentration and percentage accounting for total volatile fatty acids (TVFAs) to 21.42 g/L and 81.5%, respectively, as compared with 21.42 g/L and 10.6% of textile wastewater sludge alone. The maximum butyric acid yield (0.45 g/g VS), conversion rate (0.74 g/g VS(digest)) and production rate (2.25 g/L d) was achieved at a C/N ratio of 30. The biological toxicity of textile wastewater sludge also significantly decreased after the anaerobic digestion. The study indicated that the anaerobic co-digestion of textile wastewater sludge and carbohydrate-rich waste with appropriate C/N ratio is possible for butyric acid production.     

我国纺织染整企业废水处理相关问题探讨

通过调研,了解了我国纺织染整企业废水处理工艺流程及使用单体工艺情况.针对纺织染整企业废水处理中存在的诸如管理人员素质偏低、工艺构筑物堵塞、曝气量不足、滥用废酸、实际运行工况与设计工况严重不符、深度处理工艺难以正常运行等问题,提出了提高管理人员素质、加强对废酸监管、废水排入纺织染整废水集中处理厂处理、运用剩余污泥减量化处理工艺和选用合理的深度处理工艺等解决措施,以促进染整企业废水处理的不断发展.     

Simultaneous wastewater treatment and biological electricity generation.

It is possible to directly generate electricity using bacteria while accomplishing wastewater treatment in processes based on microbial fuel cell technologies. When bacteria oxidize a substrate, they remove electrons. Current generation is made possible by keeping bacteria separated from oxygen, but allowing the bacteria growing on an anode to transfer electrons to the counter electrode (cathode) that is exposed to air. In this paper, several advances are discussed in this technology, and a calculation is made on the potential for electricity recovery. Assuming a town of 100,000 people generate 16.4 x 10(6) L of wastewater, a wastewater treatment plant has the potential to become a 2.3 MW power plant if all the energy is recovered as electricity. So far, power densities are low, resulting in power generation rates of 150 kW/m2. Progress is being made that we believe may result in as much as 0.5 MW from wastewater treatment. The generation of electricity during wastewater treatment may profoundly affect the approach to anaerobic treatment technologies used in wastewater treatment.     

Membrane bio-reactor for textile wastewater treatment plant upgrading.

Textile industries carry out several fiber treatments using variable quantities of water, from five to forty times the fiber weight, and consequently generate large volumes of wastewater to be disposed of. Membrane Bio-reactors (MBRs) combine membrane technology with biological reactors for the treatment of wastewater: micro or ultrafiltration membranes are used for solid-liquid separation replacing the secondary settling of the traditional activated sludge system. This paper deals with the possibility of realizing a new section of one existing WWTP (activated sludge + clariflocculation + ozonation) for the treatment of treating textile wastewater to be recycled, equipped with an MBR (76 l/s as design capacity) and running in parallel with the existing one. During a 4-month experimental period, a pilot-scale MBR proved to be very effective for wastewater reclamation. On average, removal efficiency of the pilot plant (93% for COD, and over 99% for total suspended solids) was higher than the WWTP ones. Color was removed as in the WWTP. Anionic surfactants removal of pilot plant was lower than that of the WWTP (90.5 and 93.2% respectively), while the BiAS removal was higher in the pilot plant (98.2 vs. 97.1). At the end cost analysis of the proposed upgrade is reported.     

Wastewater treatment with activated pre-clarifier and planted soil filters.

With a series of buffer tank, activated pre-clarifier (SBR) and planted soil filters, it is possible to get a stable degradation and good effluent values in the case of unsteady inflow and changing concentrations. In the process presented here the activated pre-clarifier is working as a denitrification tank and the soil filter as a nitrification reactor. An automatic control manages the storm-water runoff, the water-recirculation returns the nitrate and provides a minimal feed. Experiences with this plant from 1999 to 2005 are given in this paper, research has been done in the project "Planted soil filters as a Biotechnological Process", founded by the German Federal Environment Foundation (DBU). A full scale pilot plant was built to treat wastewater from composting sides, with a 42 m3 SBR and a bed area of 2 x 550 m2 of the planted soil filters. Now, after six years of operation, the results are still satisfactory. Besides this pilot plant, landfill leakage and municipal wastewater have been treated in a technical scale plant with the same process in an 80 L SBR and 0.75 m2 vertical flow soil filter with good results.     

Long-term effects of the ozonation of the sludge recycling stream on excess sludge reduction and biomass activity at full-scale

This paper presents a full-scale experience of sludge minimization by means of short contact time ozonation in a wastewater treatment plant (WWTP) mainly fed on textile wastewater. The WWTP performance over a 3-year operational data series was analysed and compared with a two-year operation with sludge ozonation. Lab-scale respirometric tests were also performed to characterize biomass activity upstream and downstream of the ozone contact reactor. Results suggest that sludge ozonation: (1) is capable of decreasing excess sludge production by 17%; (2) partially decreases both N removal, by lowering the denitrification capacity, and P removal, by reducing biomass synthesis; (3) increases the decay rate from the typical value of 0.62 d(-1) to 1.3 d(-1); (4) decreases the heterotrophic growth yield from the typical value of 0.67 to 0.58 gCOD/gCOD.