Combined physical,chemical and biological treatments of wastewater containing organics from a semiconductor plant

Wastewater containing organics from a semiconductor plant was experimentally investigated in this study. The wastewater is characterized by strong color, high chemical oxygen demand (COD), a large amount of refractory volatile organic compounds and low biodegradability. Because of these characteristics, treatment of this wastewater by traditional activated sludge method is essentially impossible. In the present work, combined physical, chemical and biological methods were synergistically utilized to tackle the wastewater. The combined treatment consisted of air stripping, modified Fenton oxidation and sequencing batch reactor (SBR) method. Air stripping was employed to remove the majority of volatile organic components (notably isopropyl alcohol) from the wastewater, while the Fenton treatment decomposed the remaining refractory organics leading to simultaneous reductions of wastewater COD and color. After proper dilution with other low-strength, organics-containing wastewater stream, the wastewater effluent was finally treated by the SBR method. Experimental tests were conducted to determine the effectiveness and the optimum operating conditions of each treatment process. Test results clearly demonstrated the advantages of the combined treatments. The treatment train was found capable of lowering the wastewater COD concentration from as high as 80,000 mg/l to below 100mg/l and completely eliminating the wastewater color. The overall water quality of the final effluent exceeded the direct discharge standard and the effluent can even be considered for reuse.     

Pretreatment of anaerobic digestion effluent with ammonia stripping and biogas purification

In this study, ammonia stripping was optimized for pretreating anaerobic digestion effluent from an anaerobic digestion plant, and the possibility of using CO(2) stripping and biogas injection for adjusting the pH of the effluent before and after the ammonia stripping process was also investigated. For ammonia stripping, the results showed that an overdose of calcium hydroxide, i.e., 27.5g/L wastewater, achieved higher ammonia, phosphorus, chemical oxygen demand, suspended solids, and turbidity removal efficiency. An air flow rate of 5L/min for 1L of wastewater was thought as suitable for engineering application. The pH of the anaerobic digestion effluent can be increased from about 7 to about 9 by CO(2) stripping, however which is insufficient for ammonia stripping. For 1L of wastewater treated after ammonia stripping, the pH can be neutralized to about 7 from greater than 11 through biogas injection at 1L/min for less than 30min, and continuous injection does not decrease the pH. It was roughly estimated that 43m(3) of biogas (CH(4):CO(2) approximately 60%:40%) produced daily could be purified to CH(4):CO(2) approximately 74%:26% by neutralizing the pH of the 5m(3) anaerobic digestion effluent pretreated by ammonia stripping.     

Evaporation and air-stripping to assess and reduce ethanolamines toxicity in oily wastewater

Toxicity from industrial oily wastewater remains a problem even after conventional activated sludge treatment process, because of the persistence of some toxicant compounds. This work verified the removal efficiency of organic and inorganic pollutants and the effects of evaporation and air-stripping techniques on oily wastewater toxicity reduction. In a lab-scale plant, a vacuum evaporation procedure at three different temperatures and an air-stripping stage were tested on oily wastewater. Toxicity reduction/removal was observed at each treatment step via Microtox bioassay. A case study monitoring real scale evaporation was also done in a full-size wastewater treatment plant (WWTP). To implement part of a general project of toxicity reduction evaluation, additional investigations took into account the monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) role in toxicity definition after the evaporation phase, both as pure substances and mixtures. Only MEA and TEA appeared to contribute towards effluent toxicity.     

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.     

Ecotoxicological evaluation of the wastewater treatment process of the sewage treatment plant of Thessaloniki, Greece

The LUMISTox toxicity test was employed to assess the removal of municipal wastewater toxicity during the biological treatment with activated sludge in the wastewater treatment plant of Thessaloniki, Greece. Possible associations of toxicity data with chemical parameters of organic pollution of wastewaters, namely BOD(5), COD, DOC, SS and persistent organic pollutants (POPs) were also investigated. Toxicity and chemical parameters were concurrently measured at three sampling points of the treatment plant, the entrance of the unit (raw wastewater, RW), the effluent of the secondary sedimentation tank (SSE), and the final sewage sludge (FS). Substantial reduction of toxicity was observed from RW to SSE (mean+/-S.D. of bioluminescence inhibition 36+/-9.4% and 13+/-4.0%, respectively) indicating removal of toxicants during primary and secondary clarification, also suggesting that a large part of the toxicity measured is attributed to the biodegradable fraction of the organic content of wastewater. Significant positive correlations were observed between % inhibition values and wastewater parameters (BOD, COD, SS). In sludge, correlations were in general poor. Negative strong correlation was observed between EC(20/15) and TOC suggesting that the organic content of sludge contributes to the toxicity measured. Toxicity was positively correlated with the concentrations of certain POPs in RW, while weaker negative correlations were observed in SSE. Correlations in sewage sludge were less significant. It was concluded that toxicity testing is a useful tool supplementing chemical analyses in the evaluation of the potential hazard from effluent discharges and disposal of waste sludge.     

Chemical or electrochemical techniques, followed by ion exchange, for recycle of textile dye wastewater

This paper examines the use of chemical or electrocoagulation treatment process followed by ion-exchange process of the textile dye effluent. The dye effluent was treated using polymeric coagulant (cationic dye-fixing agent) or electrocoagulation (iron and aluminum electrode) process under various conditions such as various current densities and effect of pH. Efficiencies of COD reduction, colour removal and power consumption were studied for each process. The chemical or electrochemical treatment are indented primarily to remove colour and COD of wastewater while ion exchange is used to further improve the removal efficiency of the colour, COD, Fe concentration, conductivity, alkalinity and total dissolved solids (TDS). From the results chemical coagulation, maximum COD reduction of about 81.3% was obtained at 300 mg/l of coagulant whereas in electrocoagulation process, maximum COD removal of about 92.31% (0.25 A/dm2) was achieved with energy consumption of about 19.29 k Wh/kg of COD and 80% (1A/dm(2)) COD removal was obtained with energy consumption of about 130.095 k Wh/kg of COD at iron and aluminum electrodes, respectively. All the experimental results, throughout the present study, have indicated that chemical or electrocoagulation treatment followed by ion-exchange methods were very effective and were capable of elevating quality of the treated wastewater effluent to the reuse standard of the textile industry.     

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.     

Biological treatability of raw and ozonated penicillin formulation effluent

In the present study, oxidative pre-treatment of pharmaceutical wastewater originating from the formulation of the penicillin Sultamycillin Tosylate Diydrate via ozonation at varying pH and ozone feed rates was investigated. Biological treatability studies were performed with a synthetic wastewater alone and supplemented with raw and ozonated penicillin formulation effluents. The highest COD (34%) and TOC (24%) removal efficiencies were obtained at pH 11.0, whereas the BOD5 value increased from 16 mg l(-1) to 128 mg l(-1) after 40 min of ozonation, corresponding to an applied ozone dose of 1670 mg l(-1) and 33% relative ozone absorption. The studies showed that no degradation of raw penicillin fraction (30% of total COD) occurred, and degradation of the synthetic wastewater being completely treatable without penicillin addition, was inhibited by 7%. Upon 40 min ozonation, the synthetic wastewater could be completely oxidized and at the same time 35% of ozonated penicillin wastewater removal was obtained. Respirometric studies were conducted in parallel and produced results indicating a 22% decrease in the total oxygen consumption rate established for raw penicillin formulation effluent compared to the results obtained from the aerobic batch reactor. No inhibition of the synthetic fraction was observed for the 40 min-ozonated penicillin formulation effluent, biodegradability of the 60 min-ozonated penicillin effluent decreased possibly due to recalcitrant oxidation product accumulation. The modeling study provided experimental support and information on inhibition kinetics in activated sludge model no. 3 (ASM3) by means of respirometric tests for the first time.     

Toxicity studies in a chemical dye production industry in Turkey

This study investigated the acute toxicity of chemical dye production industry wastewaters by traditional and enrichment toxicity tests and emphasized the importance of toxicity tests in wastewater discharge regulations. The enrichment toxicity tests are novel applications indicating whether there is potential toxicity or stimulation conditions. Different organisms were used including bacteria (floc-Zoogloea ramigera and coliform-Escherichia coli bacteria), algae (Chlorella vulgaris), fish (lepistes-Poecilia reticulate) and protozoan (Vorticella campanula) to represent four tropic levels. The toxicity test results were compared with chemical analyses to identify the pollutants responsible for the toxicity in the effluent wastewater samples. Toxicity of the effluents could not be explained by using physicochemical analyses in four cases. The results clearly showed that the use of bioassay tests produce additional information about the toxicity potential of industrial discharges and effluents.     

Characterization of wastewater from the Brazilian TNT industry

The objective of this work was to characterize the effluent originating from a Brazilian TNT production industry. Analyses were performed using physical, chemical, spectroscopic and ecotoxicological assays, which demonstrated that the effluent had a significant pollution potential, mainly due to the low pH and high concentration of TNT (156+/-10mgL(-1)). The results also demonstrated that the effluent presented significant acute toxicity, and could cause countless damages if released into the receiving body without being adequately treated first. The observed pollution potential justifies studies to evaluate treatment technologies or recover the residue generated in the TNT industry.     

Treatment of desizing wastewater by catalytic thermal treatment and coagulation

In the present study, the coagulation of the fresh and thermally treated desizing wastewater has been reported. The maximum COD reduction of fresh desizing wastewater using coagulation was observed with commercial alum at initial pH 4. This was followed by aluminum potassium sulfate (pH 4), FeCl(3) (pH 6), PAC (pH 6) and FeSO(4) (pH 4). The maximum COD reduction observed at a coagulant (commercial alum) dose of 5 kg/m(3) and pH 4 was 58% whereas the color reduction at these conditions was 85%. The results reveal that the application of coagulation on the catalytic thermal treated effluent is more effective in removing nearly 88% of COD and 96% of color at above mentioned conditions except at a coagulant dose of 1 kg/m(3). The amount of inorganic sludge generated gets drastically reduced (almost 25%) due to the reduced amount of coagulant. The COD and color of the final effluent were found to be 98.6 mg/l and 2.67 PCU, respectively, and the COD/BOD(3) ratio was 1.36. The settling rate of the slurry was found to be strongly influenced by treatment pH. The slurry obtained after treatment at pH 12 settled faster in comparison to slurry obtained at pH 4. The filterability of the treated effluent is also strongly dependent on pH. pH 12 was adjudged to be the best in giving highest filtration rate.     

The effect of mixing pharmaceutical and tannery wastewaters on the biodegradation characteristics of the effluents

This paper evaluated the effect of mixing the effluent of a pharmaceutical plant producing acetylsalicylic acid with tannery wastewater, on the biodegradation of the effluents. The evaluation involved the analysis of the oxygen uptake rate (OUR), profiles of each wastewater and the mixture by respirometry. Model calibration using the experimental OUR data identified major COD fractions and associated process kinetics for all samples analyzed. The tannery sample was a plain-settled effluent having a total COD of around 2200 mg/L with a readily biodegradable fraction of 15%. The same fraction was 57% in the pharmaceutical wastewater sample having a much stronger total COD content of 40,435 mg/L. Consequently, mixing of the pharmaceutical effluent with the tannery wastewater up to 38% of the total COD in the mixture increased the readily biodegradable COD fraction but had an inhibitory effect on the biodegradation kinetics. This effect was relatively lower on growth, but quite significant on the hydrolysis of the slowly biodegradable COD decreasing the maximum hydrolysis rate from 2.0 day(-1) to 1.2 day(-1). Model evaluation of the respirometric data, as performed in this study sets a workable protocol for the assessment of the compatibility of different wastewater mixtures for biological treatability.     

Bench scale treatability of contaminated groundwater at the Ott/Story site - part 1

This is the first of a two-part paper describing experimental studies on the treatability of contaminated groundwater at the Ott/Story site in Muskegon, Michigan. This groundwater is severely contaminated by numerous organic compounds. Activated carbon and resin adsorption, aerobic and anaerobic biological treatment, chemical oxidation, and stripping are being investigated at the bench scale. Most treatment technologies studied to date have been moderately effective in reducing the levels of organic contamination. However, a process train consisting of granular activated carbon adsorption followed by activated sludge treatment can achieve high levels of treatment for short periods of time.     

Advanced treatment of coking wastewater by coagulation and zero-valent iron processes

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5-31.8% could be achieved under the optimal condition of coagulation, i.e. 400mg/L of Fe(2)(SO(4))3 as coagulant at pH 3.0-5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10 g/L active carbon and 30 g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation-reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000 Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process.     

Combined post-ozonation and biological treatment of recalcitrant wastewater from a resin-producing factory

In this study, effluent from the biological treatment of wastewater from a resin-producing factory containing recalcitrant compounds was ozonated under different conditions. Afterwards, the biodegradability of the ozonated effluent was studied under anoxic conditions. The post-ozonation of the industrial effluent was performed using a wide range of ozone doses, from 1.8 to 29.5 mg L(-1)min(-1). After the biological treatment of the ozonated effluent, organic carbon and nitrogen removals from 27 to 97% and from 27 to 80%, respectively, were achieved. The effect of the contact time was studied at a constant ozone dose of 13.0+/-1.2 mg L(-1)min(-1) and contact times ranging from 30 to 180 min. In this case, organic carbon removals from 55 to 100% and organic nitrogen removals from 41 to 77% were obtained after biological treatment.     

Biological treatment of wastewaters from a dye manufacturing company using a trickling filter

The aim of this work was to assess the effectiveness of a biological trickling filter for the treatment of wastewaters produced by a company manufacturing organic dyes and varnishes. The combined wastewater effluent was fed to a pilot-scale trickling filter in two feeding modes, continuously and as a sequencing batch reactor (SBR). The biodegradability of the diluted wastewaters that were subjected to physicochemical treatment, using Ca(OH)(2) and FeSO(4), was initially studied using a continuously operated trickling filter. The system efficiency ranged up to 60-70% for a hydraulic loading of 1.1 m(3)/m(2)day and up to 80-85% for a hydraulic loading 0.6 m(3)/m(2)day. A stable chemical oxygen demand (COD) removal efficiency of 60-70% was achieved even in the case of undiluted wastewater at a hydraulic loading of 1.1 m(3)/m(2)day. The effectiveness of biological treatment of a mixture of the company's main wastewater streams was also examined. The microorganisms developed in the trickling filter were able to efficiently remove COD levels up to 36,000 mg/L, under aerobic conditions at pH values between 5.5 and 8.0. Depending on the operating conditions of the system, about 30-60% of the total COD removal was attributed to air stripping caused by the air supply at the bottom of the filter, whereas the rest of the COD was clearly removed through biological action. The proposed biological treatment process based on a trickling filter, which was operated either continuously or even better in an SBR mode, appears as a promising pretreatment step for coping with dye manufacturing wastewaters in terms of removing a significant portion of the organic content.     

Toxicity of textile dyes and their degradation by the enzyme horseradish peroxidase (HRP)

The enzyme peroxidase is known for its capacity to remove phenolic compounds and aromatic amines from aqueous solutions and also to decolorize textile effluents. This study evaluates the potential of the enzyme horseradish peroxidase (HRP) in the decolorization of textile dyes and effluents. Some factors such as pH and the amount of H(2)O(2) and the enzyme were evaluated in order to determine the optimum conditions for the enzyme performance. For the dyes tested, the results indicated that the decolorization of the dye Remazol Turquoise Blue G 133% was approximately 59%, and 94% for the Lanaset Blue 2R; for the textile effluent, the decolorization was 52%. The tests for toxicity towards Daphnia magna showed that there was a reduction in toxicity after the enzymatic treatment. However, the toxicity of the textile effluent showed no change towards Artemia salina after the enzyme treatment. This study verifies the viability of the use of the enzyme horseradish peroxidase in the biodegradation of textile dyes.     

A combined electrocoagulation-sorption process applied to mixed industrial wastewater

The removal of organic pollutants from a highly complex industrial wastewater by a aluminium electrocoagulation process coupled with biosorption was evaluated. Under optimal conditions of pH 8 and 45.45 Am(-2) current density, the electrochemical method yields a very effective reduction of all organic pollutants, this reduction was enhanced when the biosorption treatment was applied as a polishing step. Treatment reduced chemical oxygen demand (COD) by 84%, biochemical oxygen demand (BOD(5)) by 78%, color by 97%, turbidity by 98% and fecal coliforms by 99%. The chemical species formed in aqueous solution were determined. The initial and final pollutant levels in the wastewater were monitored using UV-vis spectrometry and cyclic voltammetry. Finally, the morphology and elemental composition of the biosorbent was characterized with scanning electron microscopy (SEM) and energy dispersion spectra (EDS).     

Decolorization and COD reduction of UASB pretreated poultry manure wastewater by electrocoagulation process: a post-treatment study

The performance of electrocoagulation (EC) technique for decolorization and chemical oxygen demand (COD) reduction of anaerobically pretreated poultry manure wastewater was investigated in a laboratory batch study. Two identical 15.7-L up-flow anaerobic sludge blanket (UASB) reactors were first run under various organic and hydraulic loading conditions for 216 days. Effects of operating parameters such as type of sacrificial electrode material, time of electrolysis, current density, initial pH, and electrolyte concentration were further studied to optimize conditions for the post-treatment of UASB pretreated poultry manure wastewater. Preliminary tests conducted with two types of sacrificial electrodes (Al and Fe) resulted that Al electrodes were found to be more effective for both COD and color removals than Fe electrodes. The subsequent EC tests performed with Al electrodes showed that optimal operating conditions were determined to be an initial pH of 5.0, a current density of 15mA/cm(2), and an electrolysis time of 20min. The results indicated that under the optimal conditions, about 90% of COD and 92% of residual color could be effectively removed from the UASB effluent with the further contribution of the EC technology used as a post-treatment unit. In this study, the possible acute toxicity of the EC effluent was also evaluated by a static bioassay test procedure using guppy fish (Lebistes reticulatus). Findings of this study clearly indicated that incorporation of a toxicological test into conventional physicochemical analyses provided a better evaluation of final discharge characteristics.     

Electrochemical treatment of textile dyes and dyehouse effluents

The electrochemical oxidation of textile effluents over a titanium-tantalum-platinum-iridium anode was investigated. Batch experiments were conducted in a flow-through electrolytic cell with internal recirculation at current intensities of 5, 10, 14 and 20A, NaCl concentrations of 0.5, 1, 2 and 4% and recirculation rates of 0.81 and 0.65 L/s using a highly colored, synthetic effluent containing 16 textile dyes at a total concentration of 361 mg/L and chemical oxygen demand (COD) of 281 mg/L. Moreover, an actual dyehouse effluent containing residual dyes as well as various inorganic and organic compounds with a COD of 404 mg/L was tested. In most cases, quantitative effluent decolorization was achieved after 10-15 min of treatment and this required low energy consumption; conversely, the extent of mineralization varied between 30 and 90% after 180 min depending on the operating conditions and the type of effluent. In general, treatment performance improved with increasing current intensity and salinity and decreasing solution pH. However, the use of electrolytes not containing chloride (e.g. FeSO4 or Na2SO4) suppressed degradation. Although the acute toxicity of the actual effluent to marine bacteria Vibrio fischeri was weak, it increased sharply following treatment, thus suggesting the formation of persistent toxic by-products.