Purification of storage brines from the preservation of table olives

The chemical oxidation of the wastewaters generated during storage of table olives in NaCl brines, prior to their manufacturing process, was studied. Ozone alone produced COD removals in the range 14-23%, and a higher average removal of 73% of the aromatic compounds. The additional presence of hydrogen peroxide and UV radiation increased these values to 39% for COD and 86% for aromatics. However, UV radiation alone only gave a removal of 9% for COD and 27% for aromatics, and the additional presence of 0.5M H(2)O(2) led to 13% for COD and 38% for aromatics, respectively. The Fenton's reagent oxidation achieved a COD removal of 24% for the higher concentrations of Fe(2+) and H(2)O(2). The most effective process was the combination O(3)/UV/H(2)O(2) with total removals of 65 and 92% for the COD and aromatics, respectively. The aerobic treatment of these effluents gave a 66% removal regardless of the initial biomass concentration used, and a rate constant of 0.19 per day was obtained for the process by using the Contois model. Finally, the aerobic treatment of the wastewaters previously ozonated alone, and ozonated with UV radiation, gave increases in the COD removal and a final rate constant of 0.44 per day. The enhancements were due to the chemical oxidations, these procedures being suitable technologies as pre-treatments to subsequent biological processes for the purification of these residues.     

Combined advanced oxidation and biological treatment of tannery effluent

During leather processing in tanneries, considerable amount of wastes with organic and inorganic pollutants are generated. For removal of these pollutants and recovery of water, biological treatment methods and reverse osmosis (RO) based membrane technologies are adopted. While recovering water from treated tannery effluent using RO membranes, presence of residual organics, dye molecules, and other impurities in the effluent have been reported as the major drawback which leads to membrane fouling and failure. In this study, an attempt was made to improve the quality of the treated tannery effluent by subjecting the secondary treated tannery effluent by ozonation alone and ozonation of primary and secondary treated tannery effluent followed by aerobic biological Sequential Batch Reactor (SBR). Maximum color reduction of 98% at pH value of 12 with ozonation alone was observed for secondary treated tannery effluent. Ozonation of secondary treated tannery effluent followed by further biological treatment in aerobic SBR increased the chemical oxygen demand (COD) removal rate and resulted in COD values less than 300 mg/L. In case of primary treated tannery effluent, maximum COD reduction of 64% was achieved in SBR.     

COD, para-chlorophenol and toxicity removal from para-chlorophenol containing synthetic wastewater in an activated sludge unit

Chlorinated phenolic compounds present in some chemical industry wastewaters cause severe toxic effects on the organisms and often are resistant to biological degradation. Synthetic wastewater containing different concentrations of para-chlorophenol (4-chlorophenol, 4-CP) was biologically treated in an activated sludge unit for COD, 4-CP and toxicity removal. Effects of feed 4-CP concentration on COD, 4-CP, toxicity removals and on sludge volume index were investigated at a constant sludge age of 20 days and hydraulic residence time (HRT) of 25 h. Resazurin method based on dehydrogenase activity was used for determination of the toxicity of the feed and effluent wastewater. COD and 4-CP removals were not affected by the presence of 4-CP in the wastewater up to feed 4-CP concentration of 925 mg l(-1) because of almost complete degradation of 4-CP yielding lower than 50 mg l(-1) 4-CP in the aeration tank. Percent COD, 4-CP and toxicity removals decreased and the effluent COD, 4-CP and toxicity levels increased with further increases in the feed 4-CP concentrations above 925 mg l(-1) because of inhibitory concentrations of 4-CP in the reactor. Biomass concentration in the aeration tank decreased and the sludge volume index (SVI) increased with feed 4-CP concentrations above 925 mg l(-1) resulting in lower COD and 4-CP removal rates. The rates of COD and 4-CP removals indicated substrate (4-CP) inhibition for the feed 4-CP concentrations above 925 mg l(-1) corresponding to the reactor 4-CP of above 200 mg l(-1). The system should be operated at the feed 4-CP concentrations of less than 900 mg l(-1) (4-CP(R) < 200 mg l(-1)) in order to obtain high rates and extents of COD, 4-CP and toxicity removals at a sludge age of 20 days and HRT of 25 h.     

Performance of a hybrid-loop bioreactor system in biological treatment of 2,4,6-tri-chlorophenol containing synthetic wastewater: effects of hydraulic residence time

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with effluent recycle was used for biological treatment of 2,4,6-tri-chlorophenol (TCP) containing synthetic wastewater. Effects of hydraulic residence time (HRT) on COD, TCP and toxicity removal performance of the reactor were investigated for the HRT values between 5 and 30 h, while the feed COD (2700+/-100 mgl(-1)), TCP (300+/-10 mgl(-1)) and the solids retention time (sludge age, SRT, 20 d) were constant. Percent TCP, COD and toxicity removals increased with increasing HRT resulting in more than 90% COD, TCP and toxicity removals at HRT values above 25 h. Biomass concentrations in the packed column and in the aeration tank increased with increasing HRT resulting in low reactor TCP concentrations and therefore high TCP, COD and toxicity removals at high HRT values. Volumetric and specific rates of TCP and COD removals decreased with increasing HRT due to increased biomass and decreased flow rates at high HRT levels. Volumetric and specific removal rates of COD and TCP were maximum at an HRT of 5 h.     

Elimination of Cu(II) toxicity by powdered waste sludge (PWS) addition to an activated sludge unit treating Cu(II) containing synthetic wastewater

Copper(II) ion toxicity onto activated sludge organisms was eliminated by addition of powdered waste sludge (PWS) to the feed wastewater for removal of Cu(II) ions by biosorption before biological treatment. The synthetic feed wastewater containing 14 or 22 mgl(-1) Cu(II) was mixed with PWS in a mixing tank where Cu(II) ions were adsorbed onto PWS and the mixture was fed to a sedimentation tank to separate Cu(II) containing PWS from the feed wastewater. The activated sludge unit fed with the effluent of the sedimentation tank was operated at a hydraulic residence time (HRT) of 10h and sludge age (SRT) of 10 days. To investigate Cu(II), COD and toxicity removal performance of the activated sludge unit at different PWS loadings, the system was operated at different PWS loading rates (0.1-1 gPWSh(-1)) while the Cu(II) loading rate was constant throughout the operation. Percent copper, COD and toxicity removals increased with increasing PWS loading rate due to increased adsorption of Cu(II) onto PWS yielding low Cu(II) contents in the feed. Biomass concentration in the aeration tank increased and the sludge volume index (SVI) decreased with increasing PWS loading rate due to elimination of Cu(II) from the feed wastewater by PWS addition. PWS addition to the Cu(II) containing wastewater was proven to be effective for removal of Cu(II) by biosorption before biological treatment. Approximately, 1 gPWSh(-1) should be added for 28 mgCuh(-1) loading rate for complete removal of Cu(II) from the feed wastewater to obtain high COD removals in the activated sludge unit.     

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.     

Biological treatment of para-chlorophenol containing synthetic wastewater using rotating brush biofilm reactor

A novel rotating brush biofilm reactor (RBBR) was used for para-chlorophenol (4-chlorophenol, 4-CP), COD and toxicity removal from synthetic wastewater containing different concentrations of 4-CP. Effects of major operating variables such as the feed 4-CP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio on the performance of the biofilm reactor were investigated. A Box-Wilson statistical experiment design method was used by considering the feed 4-CP (0-1000 mg l(-1)), COD (2000-6000 mg l(-1)) and A/Q ratio (73-293 m(2) day m(-3)) as the independent variables while the 4-CP, COD and toxicity removals were the objective functions. The results were correlated by a response function and the coefficients were determined by regression analysis. Percent 4-CP, COD and toxicity removals determined from the response functions were in good agreement with the experimental results. 4-CP, COD and toxicity removals increased with decreasing feed 4-CP and increasing A/Q ratio. Optimum conditions resulting in maximum COD, 4-CP and toxicity removals were found to be A/Q ratio of nearly 180 m(2) day m(-3), feed COD of nearly 4000 mg l(-1) and feed 4-CP of less than 205 mg l(-1).     

Mathematical modelling of 4-chlorophenol inhibition on COD and 4-chlorophenol removals in an activated sludge unit

A mathematical model was developed for an activated sludge unit treating 4-chlorophenol (4-CP) containing synthetic wastewater composed of diluted molasses, urea, KH(2)PO(4) and MgSO(4) with COD and 4-CP contents of 2500 and 500 mg l(-1), respectively. The model included 4-CP inhibition on COD and 4-CP removals. Experimental data obtained at different hydraulic residence times (HRT=5-30h) and sludge ages (SRT, 3-30 days) were used to estimate the kinetic and inhibition constants for COD and 4-CP removal rates. 4-CP inhibition on COD removal was negligible while the inhibition on 4-CP removal was significant. The specific rate constant (k), saturation constant (K(s)) for COD oxidation were found to be 2.64 day(-1) and 559 mg l(-1), respectively. A similar model was used for 4-CP oxidation in the activated sludge unit and the constants were found to be k'=1.44 day(-1), K'(s)=25.7 mgl(-1), K"(CP)=559 mg l(-1),and K(I,CP)=17 mg l(-1). Increases in death rate constant because of 4-CP inhibition was also quantified and the inhibition constants were determined for both COD and 4-CP removals. Model predictions with the estimated kinetic constants were in good agreement with the experimental data. Developed model can be used to estimate the performance of an activated sludge unit treating 4-CP containing wastewater under the specified experimental conditions.     

Electrochemical degradation of amaranth aqueous solution on ACF

The degradation of Amaranth, a kind of azo dye, has been studied under galvanostatic model with activated carbon fiber (ACF) electrode in aqueous solution with electrochemical method. The ACF was used as anode and cathode, respectively for the decolorization process. The onset oxidation potential and reduction potential for Amaranth on ACF were respectively ascertained at 0.6 and -0.4 V. During the range of -1.1 to 0.50 mA cm(-2), the decolorization was clarified into three processes as electroreduction, adsorption and electrooxidation. There were little contributions to the color and COD removals for the process of adsorption. The color removal can be up to 99% when the current density was 0.50 mA cm(-2). The maximum COD removal was 52% for the process of electrooxidation. Hundred percent color removal was obtained when the current density of -1.0 mA cm(-2) was applied. The maximum COD removal was 62% for the electroreduction. The COD removal results from the adsorption of products for the decolorization process of electrooxidation or electroreduction.     

超声空化作用于水中天然有机质特性研究

利用超声空化作用去除水中天然有机质(Natural Organic Matter,简称NOM)不会产生消毒副产物.研究了采用低频高功耗率的超声处理富里酸溶液,结果表明:由于超声空化的热解及氧化作用,随着声功率及富里酸溶液浓度的增加,溶液的pH、ORP逐渐减小,溶液的温度、浊度逐渐增加,体系中加入盐酸后能够放大超声作用.作为水中NOM浓度的替代参数,UV<,254>在超声作用下缓慢增加,而总有机碳(TOC)的超声降解符合准一级反应规律,在20min超声作用之后,TOC去除率由21.2%增至31.6%,加入盐酸后,由24.7%增至34.8%.该研究可为超声协同其他工艺进行水处理提供放大设计依据.     

Degradation of recalcitrant compounds from stabilized landfill leachate using a combination of ozone-GAC adsorption treatment

Laboratory experiments were undertaken to investigate the treatment performances of ozonation alone and/or its combination with granular activated carbon (GAC) adsorption for raw leachate from the NENT landfill (in Hong Kong). To improve its removal of recalcitrant contaminants from the leachate, the surface of GAC was oxidized with ozone prior to treatment. With respect to ozone dose and pH, the removal of COD and/or NH(3)-N from ozonation alone and combined ozone-GAC adsorption were evaluated and compared to those of other physico-chemical treatments in some reported studies. The removal mechanism of recalcitrant compounds by ozone-GAC adsorption treatment was presented. Among the various treatments studied, the combination of ozone-GAC adsorption using ozone-modified GAC had the highest removal for COD (86%) and/or NH(3)-N (92%) compared to ozonation alone (COD: 35%; NH(3)-N: 50%) at the same initial COD and/or NH(3)-N concentrations of 8000 and 2620 mg/L, respectively. Although the integrated treatment was more effective than ozonation alone for treating stabilized leachate, the results suggested that it could not generate treated effluent that complied with the COD limit of lower than 200 mg/L and the NH(3)-N discharge standard of less than 5 mg/L. Therefore, further biological treatments to complement the degradation of the leachate are still required to meet the environmental legislation.     

Comparison of different treatment strategies for industrial landfill leachate

The aim of our research was to determine appropriate treatment technique for effective treatment of heavily polluted tannery landfill leachate. We have accomplished several treatment experiments: (i) aerobic biological treatment, (ii) air stripping at various pH, (iii) adsorption to activated carbon, (iv) coagulation-flocculation and (v) advanced oxidation process with Fe(2+)/H(2)O(2). Efficiency of each procedure was monitored by chemical analysis and changes in biodegradability and acute toxicity were also evaluated (Vibrio fischeri and Daphnia magna). Biological treatment of raw leachate was effective only for very diluted leachate (up to 6Vol.%). It has been confirmed that air stripping at pH 11.0 effectively removed volatile organics and ammonia for 33% and 84%, respectively and contributed to lower toxicity of the leachate. Fenton's oxidation was the most effective among all used treatment procedures. COD removal reached 86%, biodegradability has been increased and toxicity reduced. Adsorption to activated carbon increased BOD(5)/COD ratio from 0.18 to 0.56 and it removed 40% of organics. Coagulation and flocculation procedures with FeCl(3) were also very effective. At lowered pH and added flocculant treatment efficiency reached 50%. But no method alone was effective enough to meet effluent limits for release into local surface waters. Future work was focused on the study of different promising treatment schemes, especially combination of Fenton's oxidation and biological treatment.     

COD, 2,4,6-trichlorophenol (TCP) and toxicity removal from synthetic wastewater in a rotating perforated-tubes biofilm reactor

Synthetic wastewater containing different concentrations of 2,4,6-trichlorophenol (TCP) was biologically treated using a novel rotating perforated-tubes biofilm reactor (RTBR) for chemical oxygen demand (COD), TCP and toxicity removal. Performance of the reactor was investigated as function of major operating variables such as the feed TCP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio. A Box-Behnken statistical experiment design method was used by considering the feed TCP (0-400 mg L(-1)), COD (1,000-4,000 mg L(-1)) and A/Q ratio (23-163 m(2)dm(-3)) as the independent variables while percent TCP, COD, and toxicity removals were the objective functions. The results were correlated with the quadratic model since this was found to be the most suitable one. Response function coefficients were determined by correlating the experimental data with the response function. Percent TCP, COD and toxicity removals estimated from the response functions were in good agreement with the experimental results. TCP, COD and toxicity removals increased with increasing A/Q ratio and decreasing feed TCP concentrations. Percent toxicity removals were always lower than TCP removals indicating presence or formation of some toxic by products from TCP biodegradation. For the feed TCP of 400 mg L(-1), the optimum conditions resulting in maximum COD (99%), TCP (100%) and toxicity (93%) removals were A/Q ratio of nearly 165 m(2)dm(-3) and feed COD of 2,985 mg L(-1).     

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.     

自制粉煤灰陶粒填料处理城市污水

利用粉煤灰、黏土、脱水污泥和碳酸钙等原料制备粉煤灰陶粒。通过正交试验确定原料的最优配比,并对自制陶粒进行了性能表征,进一步利用自制曝气生物滤池装置,通过改变运行参数,测试了自制陶粒用作曝气生物滤池填料处理城市污水的效果。结果表明:自制陶粒填料各项性能都符合相关标准;化学需氧量(COD)、总氮(TN)去除率随着水力停留时间(HRT)的增加而增加,当HRT为4h时,总磷(TP)去除率达到最大;低温不利于TN、TP的去除,温度对COD去除率影响不大;当进水中的TN含量为30mg/L时,TN去除率最大。TP去除率随着进水中的TP含量的增加而增加,进水浓度对COD去除率影响不大。     

Ozone and membrane filtration based strategies for the treatment of cork processing wastewaters

The degradation of the pollutant organic matter present in the cork processing wastewater was studied by combining chemical treatments, which used ozone and some Advanced Oxidation Processes, and membrane filtration procedures. Two schemes were conducted: firstly, a single ozonation stage followed by an UF stage; and secondly, a membrane filtration stage, using different MF and UF membranes, followed by a chemical oxidation stage, where ozone, UV radiation, and the AOPs constituted by ozone plus UV radiation and ozone plus hydrogen peroxide, were used. The membrane filtration stages were carried out in tangential filtration laboratory equipment, and the membranes used were two MF membranes with pores sizes of 0.65 and 0.1microm, and three UF membranes with molecular weights cut-off of 300, 10, and 5kDa. The effectiveness of the different stages (conversions in the chemical procedures and rejection coefficients in the membrane processes) were evaluated in terms of several parameters which measure the global pollutant content of the wastewater: COD, absorbance at 254nm, tannins content, color, and ellagic acid. In the ozonation/UF combined process the following removals were achieved: 100% for ellagic acid and color, 90% for absorbance at 254nm, more than 80% for tannins, and 42-57% for COD reduction. In the filtration/chemical oxidation combined process, 100% elimination of ellagic acid, more than 90% elimination in color, absorbance at 254nm and tannins, and removal higher than 80% in COD were reached, which indicates a greater purification power of this combination.     

Simultaneous removal of C, N, P from cheese whey by jet loop membrane bioreactor (JLMBR)

The membrane bioreactor (MBR) used in this study consisted of a jet loop bioreactor (aerobic high rate system) and a membrane separation unit (microfiltration). Jet loop membrane bioreactor (JLMBR) system is a high performance treatment system. High organic loading rates can be achieved with a very small footprint. The JLMBR is a compact biological treatment system which requires much smaller tank volumes than conventional activated sludge system. Solid-liquid separation is performed with a membrane. The JLMBR system, of 35 L capacity, was operated continuously for 3 months with a sludge age of 1.1-2.8 days and chemical oxygen demand (COD) loads of 3.5-33.5 kg COD m(-3) day(-1). The mean concentration values of COD, total nitrogen (TN) and PO(4)3- in cheese whey (CW) were found as 78,680 mg L(-1), 1125 mg L(-1) and 378 mg L(-1), respectively. Ninety-seven percent COD removal rate was obtained at the sludge age (Thetac) of 1.6 days and volumetric loads of 22.2 kg COD m(-3) day(-1). TN removal was obtained as 99% at the loading rates of 17-436 g TN m(-3) day(-1). PO4(3-) removals were between 65 and 88% for the loading of 30-134 gPO4(3-) m(-3) day(-1). The system could simultaneously remove the COD, TN and PO(4)3- at high efficiencies. The sludge flocks were highly motile, dispersed and had poor settling properties.     

Effects of adsorbents and copper(II) on activated sludge microorganisms and sequencing batch reactor treatment process

Wastewater treatment systems employing simultaneous adsorption and biodegradation processes have proven to be effective in treating toxic pollutants present in industrial wastewater. The objective of this study is to evaluate the effect of Cu(II) and the efficacy of the powdered activated carbon (PAC) and activated rice husk (ARH) in reducing the toxic effect of Cu(II) on the activated sludge microorganisms. The ARH was prepared by treatment with concentrated nitric acid for 15 h at 60-65 degrees C. The sequencing batch reactor (SBR) systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the ratio of 0.5:3.5:1:0.75:0.25 for a cycle time of 6 h. The Cu(II) and COD removal efficiency were 90 and 85%, respectively, in the SBR system containing 10 mg/l Cu(II) with the addition of 143 mg/l PAC or 1.0 g PAC per cycle. In the case of 715 mg/l ARH or 5.0 g ARH per cycle addition, the Cu(II) and COD removal efficiency were 85 and 92%, respectively. ARH can be used as an alternate adsorbent to PAC in the simultaneous adsorption and biodegradation wastewater treatment process for the removal of Cu(II). The specific oxygen uptake rate (SOUR) and kinetic studies show that the addition of PAC and ARH reduce the toxic effect of Cu(II) on the activated sludge microorganisms.     

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.     

Potential method to improve the treatment efficiency of persistent contaminants in industrial wastewater

The objective of this work was to evaluate a potential method for improving the treatment efficiency of persistent contaminants in industrial wastewater. Adsorption with powdered activated carbon (PAC) was applied as pre-treatment and operational conditions as pH, temperature, carbon concentration and time were investigated in laboratory scale for different streams generated in a fine chemical industry. Chemical oxygen demand (COD) removal efficiencies of 63 and 50% were attained for two important industrial streams, Product C after acid treatment and precipitation and Influent, at pH 7, room temperature and with 5 and 15 g l(-1) of PAC, respectively. Biodegradation assays showed that PAC adsorption enhanced COD removal efficiency. PAC pre-treatment increased the COD removal of Product C after production stream from 15 to 80% and improved the biodegradability of the Influent stream by 50%.