Cotton yarn and fabric finishing wastewater treatment in upflow anaerobic filter

Summary Wastewater from cotton yarn and fabric finishing was successfully treated in an upflow anaerobic filter at 35°C up to a COD loading of 1 Kgr COD/m³ · day; the COD removal varied from 50 to 90% and production of biogas was 0,2–0.4 L/g influent COD, having 70–80% CH₄. At higher COD loading biogas production stopped although COD removal remainedca 50%.     

Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatment

Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l(-1)) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (> 95%) compared to the unaerated control bioreactor (approximately 65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l(-1)). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l(-1)), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality.     

Biological treatment of ammonium-rich wastewater by partial nitritation and subsequent anaerobic ammonium oxidation (anammox) in a pilot plant

In wastewater treatment plants with anaerobic sludge digestion, 15-20% of the nitrogen load is recirculated to the main stream with the return liquors from dewatering. Separate treatment of this ammonium-rich digester supernatant would significantly reduce the nitrogen load of the activated sludge system. Some years ago, a novel biological process was discovered in which ammonium is converted to nitrogen gas under anoxic conditions with nitrite as the electron acceptor (anaerobic ammonium oxidation, anammox). Compared to conventional nitrification and denitrification, the aeration and carbon-source demand is reduced by over 50 and 100%, respectively. The combination of partial nitritation to produce nitrite in a first step and subsequent anaerobic ammonium oxidation in a second reactor was successfully tested on a pilot scale (3.6 m(3)) for over half a year. This report focuses on the feasibility of nitrogen removal from digester effluents from two different wastewater treatment plants (WWTPs) with the combined partial nitritation/anammox process. Nitritation was performed in a continuously stirred tank reactor (V=2.0 m(3)) without sludge retention. Some 58% of the ammonium in the supernatant was converted to nitrite. At 30 degrees C the maximum dilution rate D(x) was 0.85 d(-1), resulting in nitrite production of 0.35 kg NO(2)-N m(-3)(reactor) d(-1). The nitrate production was marginal. The anaerobic ammonium oxidation was carried out in a sequencing batch reactor (SBR, V=1.6 m(3)) with a nitrogen elimination rate of 2.4 kg N m(-3)(reactor) d(-1) during the nitrite-containing periods of the SBR cycle. Over 90% of the inlet nitrogen load to the anammox reactor was removed and the sludge production was negligible. The nitritation efficiency of the first reactor limited the overall maximum rate of nitrogen elimination.     

Anaerobic digestion and wastewater treatment systems

Upflow Anaerobic Sludge Bed (UASB) wastewater (pre-)treatment systems represent a proven sustainable technology for a wide range of very different industrial effluents, including those containing toxic/inhibitory compounds. The process is also feasible for treatment of domestic wastewater with temperatures as low as 14–16° C and likely even lower. Compared to conventional aerobic treatment systems the anaerobic treatment process merely offers advantages. This especially is true for the rate of start-up. The available insight in anaerobic sludge immobilization (i.e. granulation) and growth of granular anaerobic sludge in many respects suffices for practice. In anaerobic treatment the immobilization of balanced microbial communities is essential, because the concentration of intermediates then can be kept sufficiently low.So far ignored factors like the death and decay rate of organisms are of eminent importance for the quality of immobilized anaerobic sludge. Taking these factors into account, it can be shown that there does not exist any need for phase separation when treating non- or slightly acidified wastewaters. Phase separation even is detrimental in case the acidogenic organisms are not removed from the effluent of the acidogenic reactor, because they deteriorate the settleability of granular sludge and also negatively affect the formation and growth of granular sludge. The growing insight in the role of factors like nutrients and trace elements, the effect of metabolic intermediates and end products opens excellent prospects for process control, e.g. for the anaerobic treatment of wastewaters containing mainly methanol.Anaerobic wastewater treatment can also profitably be applied in the thermophilic and psychrophilic temperature range. Moreover, thermophilic anaerobic sludge can be used under mesophilic conditions.The Expanded Granular Sludge Bed (EGSB) system particularly offers big practical potentials, e.g. for very low strength wastewaters (COD 1 g/l) and at temperatures as low as 10° C. In EGSB-systems virtually all the retained sludge is employed, while compared to UASB-systems also a substantially bigger fraction of the immobilized organisms (inside the granules) participates in the process, because an extraordinary high substrate affinity prevails in these systems. It looks necessary to reconsider theories for mass transfer in immobilized anaerobic biomass.Instead of phasing the digestion process, staging of the anaerobic reactors should be applied. In this way mixing up of the sludge can be significantly reduced and a plug flow is promoted. A staged process will provide a higher treatment efficiency and a higher process stability. This especially applies for thermophilic systems.     

Slaughterhouse wastewater treatment: evaluation of a new three-phase separation system in a UASB reactor.

The anaerobic treatment of the wastewater from the meat processing industry was studied using a 7.2 1 UASB reactor. The reactor was equipped with an unconventional configuration of the three-phase separation system. The effluent was characterized in terms of pH (6.3-6.6), chemical oxygen demand (COD) (2,000-6,000 mg l(-1)), biochemical oxygen demand BOD5 (1,300-2,300 mg 1(-1)), fats (40-600 mg l(-1)) and total suspended solids (TSS) (850-6,300 mg l(-1)) The reactor operated continuously throughout 80 days with hydraulic retention time of 14, 18 and 22 h. The wastewater from Rezende Industrial was collected after it had gone through pretreatment (screening, flotation and equalization). COD, BOD and TSS reductions and the biogas production rate were the parameters considered in analyzing the efficiency of the process. The average production of biogas was 111 day(-1) (STP) for the three experimental runs. COD removal varied from 77% to 91% while BOD removal was 95%. The removal of total suspended solids varied from 81% to 86%. This fact supports optimal efficiency of the proposed three-phase separation system as well as the possibility of applying it to the treatment of industrial effluents.     

Performance of an ecological treatment system at three strengths of dairy wastewater loading

Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO₄-P, TP, TN, NH₄-N, NO₃-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD₅). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO₄-P was reduced 39%, TN 83%, and NH₄-N 89%, while at the highest wastewater strength, PO₄-P was reduced 41%, TN 79%, and NH₄-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH₄-N and CBOD₅.     

Evaluation of the efficacy of upflow anaerobic sludge blanket reactor in removal of colour and reduction of COD in real textile wastewater

The upflow anaerobic sludge blanket (UASB) reactor was evaluated for its efficacy in decolourization and reduction in chemical oxygen demand (COD) of real textile wastewater (RTW) under different operational conditions. The efficiency of UASB reactor in reducing COD was found to be over 90%. Over 92% of colour removal due to biodegradation was achieved. The activities of the anaerobic granules were not affected during the treatment of textile wastewater. Cocci-shaped bacteria were the dominant group over Methanothrix like bacteria in textile wastewater treatment. Alkalinity, volatile fatty acids (VFA) content and pH in effluents indicated that the anaerobic process was not inhibited by textile wastewater. It is concluded that UASB reactor system can effectively be used in the treatment of textile wastewater for the removal of colour and in the reduction of COD.     

Sequencing batch biofilter granular reactor for textile wastewater treatment

Textile wastewater is difficult to treat as it usually contains considerable amounts of different pollutants, which are often recalcitrant, toxic and inhibitory. Therefore, complex treatment schemes based on the sequence of various steps are usually required for an effective treatment. This explains why textile effluents are often treated in centralized plants and sometimes mixed with municipal wastewater. The adoption of new technologies for on-site treatment, instead, would be optimal, deeply reducing treatment costs. An innovative technology exhibiting several characteristics appropriate for the attainment of such a goal is sequencing batch biofilter granular reactor (SBBGR). To assess the suitability of this technology, two lab-scale reactors were operated, treating mixed municipal-textile wastewater and a pure textile effluent, respectively. Results have demonstrated that mixed wastewater can be successfully treated with very low hydraulic retention times (less than 10 hours). Furthermore, SBBGR shows to be an effective pre-treatment for textile wastewater for discharge into sewer systems. The economic evaluation of the process showed operative costs of 0.10 and 0.19 € per m(3) of mixed wastewater and textile wastewater, respectively.     

Distribution and behavior of sludge in upflow reactors for anaerobic treatment of wastewater

A model has been developed and experimentally checked for the physical behavior of sludge in the blanket in upflow reactors. The model is based on the mass balance for the sludge in the blanket, and can be used to predict the distribution of sludge in an upflow reactor in relation with the gas production, sludge settling characteristics, and the linear fluid velocity in the reactor. The quantitative values of the transport factors that are a measure of the efficiency of the transport of sludge by the fluid streams occurring in the reactor were determined experimentally in reactors of 30- and 200-m(3) volumes. As this was done for wastewater containing lower fatty acids as the main organic pollutants and for sludge with good settling characteristics, the predictive value of the model is limited. It may be used for the second (methane forming) step of anaerobic treatment of wastewater.     

Thermophilic biological nitrogen removal in industrial wastewater treatment

Nitrification is an integral part of biological nitrogen removal processes and usually the limiting step in wastewater treatment systems. Since nitrification is often considered not feasible at temperatures higher than 40 °C, warm industrial effluents (with operating temperatures higher than 40 °C) need to be cooled down prior to biological treatment, which increases the energy and operating costs of the plants for cooling purposes. This study describes the occurrence of thermophilic biological nitrogen removal activity (nitritation, nitratation, and denitrification) at a temperature as high as 50 °C in an activated sludge wastewater treatment plant treating wastewater from an oil refinery. Using a modified two-step nitrification–two-step denitrification mathematical model extended with the incorporation of double Arrhenius equations, the nitrification (nitrititation and nitratation) and denitrification activities were described including the cease in biomass activity at 55 °C. Fluorescence in situ hybridization (FISH) analyses revealed that Nitrosomonas halotolerant and obligatehalophilic and Nitrosomonas oligotropha (known ammonia-oxidizing organisms) and Nitrospira sublineage II (nitrite-oxidizing organism (NOB)) were observed using the FISH probes applied in this study. In particular, this is the first time that Nitrospira sublineage II, a moderatedly thermophilic NOB, is observed in an engineered full-scale (industrial) wastewater treatment system at temperatures as high as 50 °C. These observations suggest that thermophilic biological nitrogen removal can be attained in wastewater treatment systems, which may further contribute to the optimization of the biological nitrogen removal processes in wastewater treatment systems that treat warm wastewater streams.     

Performances and microbial features of an aerobic packed-bed biofilm reactor developed to post-treat an olive mill effluent from an anaerobic GAC reactor

Background  

Olive mill wastewater (OMW) is the aqueous effluent of olive oil producing processes. Given its high COD and content of phenols, it has to be decontaminated before being discharged. Anaerobic digestion is one of the most promising treatment process for such an effluent, as it combines high decontamination efficiency with methane production. The large scale anaerobic digestion of OMWs is normally conducted in dispersed-growth reactors, where however are generally achieved unsatisfactory COD removal and methane production yields. The possibility of intensifying the performance of the process using a packed bed biofilm reactor, as anaerobic treatment alternative, was demonstrated. Even in this case, however, a post-treatment step is required to further reduce the COD. In this work, a biological post-treatment, consisting of an aerobic biological "Manville" silica bead-packed bed aerobic reactor, was developed, tested for its ability to complete COD removal from the anaerobic digestion effluents, and characterized biologically through molecular tools.     

Development of anaerobic sludge bed (ASB) reactor technologies for domestic wastewater treatment: motives and perspectives

During the treatment of raw domestic wastewater in the upflow anaerobic sludge blanket (UASB) reactor, the suspended solids (SS) present in the wastewater tend to influence negatively the methanogenic activity and the chemical oxygen demand (COD) conversion efficiency. These problems led to the emergence of various anaerobic sludge bed systems such as the expanded granular sludge bed (EGSB), the upflow anaerobic sludge blanket (UASB)-septic tank, the hydrolysis upflow sludge bed (HUSB), the two-stage reactor and the anaerobic hybrid (AH) reactor. However, these systems have, like the UASB reactor, limited performance with regard to complete treatment (e.g., removal of pathogens). In this respect, a new integrated approach for the anaerobic treatment of domestic wastewater is suggested. This approach combines a UASB reactor and a conventional completely stirred tank reactor (CSTR) for the treatment of the wastewater low in SS and sedimented primary sludge, respectively. The principal advantages of the proposed system are energy recovery from organic waste in an environmentally friendly way; lowering the negative effect of suspended solids in the UASB reactor; production of a high quality effluent for irrigation; and prevention of odour problems.     

Challenge of psychrophilic anaerobic wastewater treatment

Psychrophilic anaerobic treatment is an attractive option for wastewaters that are discharged at moderate to low temperature. The expanded granular sludge bed (EGSB) reactor has been shown to be a feasible system for anaerobic treatment of mainly soluble and pre-acidified wastewater at temperatures of 5--10 degrees C. An organic loading rate (OLR) of 10--12 kg chemical oxygen demand (COD) per cubic meter reactor per day can be achieved at 10--12 degrees C with a removal efficiency of 90%. Further improvement might be obtained by a two-module system in series. Stabile methanogenesis was observed at temperatures as low as 4--5 degrees C. The specific activity of the mesophilic granular sludge was improved under psychrophilic conditions, which indicates that there was growth and enrichment of methanogens and acetogens in the anaerobic system. Anaerobic sewage treatment is a real challenge in moderate climates because sewage belongs to the 'complex' wastewater category and contains a high fraction of particulate COD. A two-step system consisting of either an anaerobic up-flow sludge bed (UASB) reactor combined with an EGSB reactor or an anaerobic filter (AF) combined with an anaerobic hybrid reactor (AH) is successful for anaerobic treatment of sewage at 13 degrees C with a total COD removal efficiency of 50% and 70%, respectively.     

Continuous anaerobic treatment of wastewater from a kraft pulp mill

A pilot-scale study of the thermophilic anaerobic digestion of high-strength wastewater (evaporator condensate, EC) discharged from a kraft pulp production process was performed. The system consisted of a microfiltration (MF) membrane module for oily substances removal, a stripping system using evolved gas from the digester for sulfur compounds removal, an anaerobic fixed-bed bioreactor for methane fermentation, and an ultrafiltration (UF) membrane module for retention of a high density of bacterial cells. The bioreactor had a fixed-bed with an effective volume of 5 m³ packed with pumice stone. In a continuous run with only the MF membrane module for oily substances removal, the digester efficiency declined because of methanogenic inhibition by sulfur compounds. After fitting of the stripping system which used evolved gas from the digester, the inhibitive sulfur compounds in the EC were removed more than 80%, and high-loading and high-efficiency operation could be attained. The BOD loading and BOD removal of 35.5 kg BOD/m³/d and 93%, respectively were attained. By anaerobic treatment of the evaporator condensate waste before the conventional aerobic activated sludge method, the total costs would be reduced to ¥3.31/m³ wastewater compared with ¥4.53/m³-wastewater by the aerobic activated sludge method only. The stability of digester performance against interruption by feed stoppage was also examined.     

Anaerobic treatment of antibiotic production wastewater and kinetic evaluations

In this study, the anaerobic treatment of high-strength antibiotic production wastewater and the development of a mathematical model for the treatment were attempted. Anaerobic treatability was investigated using synthetic solutions and original wastewater of which the initial chemical oxygen demand (COD) was determined. Initial COD of solutions was increased from 3,000 to 43,000 mg O(2)/liter in an anaerobic bioreactor. The bioreactor pH was maintained at 6.5-7.5. The temperature was kept constant at 37 +/- 1 degrees C. Raw materials and original wastewater containing penicillin antibiotics were obtained from Fako Pharmaceutical Factory (Fako) in Istanbul, Turkey. Anaerobic sludge used for treatment was obtained from Pakmaya Baker's Yeast Producing Factory (Pakmaya) in Izmit, Turkey and the Fako. A mathematical model based on substrate (total COD) concentration was developed assuming that only three consecutive reactions, namely, hydrolysis, acidogenesis and methanogenesis, are significant. From the experimental data, a model that can be used for COD calculation as a function of time was developed using the first- and the second-order kinetic approaches. Making use of the developed model equation, it was proved that the anaerobic treatment of high strength (COD > 25,000 mg O(2)/liter) antibiotic production wastewater fits the second-order kinetics.     

A two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater

A two-stage ultrafiltration and nanofiltration (UF/NF) process for the treatment of model dairy wastewater was investigated to recycle nutrients and water from the wastewater. Ultracel PLGC and NF270 membranes were found to be the most suitable for this purpose. In the first stage, protein and lipid were concentrated by the Ultracel PLGC UF membrane and could be used for algae cultivation to produce biodiesel and biofuel, and the permeate from UF was concentrated by the NF270 membrane in the second stage to obtain lactose in retentate and reusable water in permeate, while the NF retentate could be recycled for anaerobic digestion to produce biogas. With this approach, most of dairy wastewater could be recycled to produce reusable water and substrates for bioenergy production. Compared with the single NF process, this two-stage UF/NF process had a higher efficiency and less membrane fouling.     

Implementation of batchwise bioscouring of cotton knits

The examination of critical factors determining the performance of bioscouring showed that a short treatment of the fabric at greater than 80°C after pectinase treatment at 60°C was essential for removal of waxes from the fabric as demonstrated by diminished intensities of methylene peaks in FT-IR measurements. Batch-wise bioscouring of cotton knits was carried out several times with post-treatment at 80°C using a rapid dyeing machine. The dye-ability of bioscoured knits was as good as the company's alkaline scoured ones with slightly higher K/S values. Water pollution caused by effluents of bioscouring and alkaline processes were estimated, as well as that due to the input of chemicals and enzymes. Higher BOD:COD_Cr ratios for enzymes indicated their biodegradable character. After calculation of energy consumption using a simulation program, an economic evaluation of the two processes was done on the basis of one ton production by considering the costs of chemicals and enzyme, water usage, energy consumption and waste water treatment charge.     

Implementation of batchwise bioscouring of cotton knits

The examination of critical factors determining the performance of bioscouring showed that a short treatment of the fabric at greater than 80°C after pectinase treatment at 60°C was essential for removal of waxes from the fabric as demonstrated by diminished intensities of methylene peaks in FT-IR measurements. Batch-wise bioscouring of cotton knits was carried out several times with post-treatment at 80°C using a rapid dyeing machine. The dye-ability of bioscoured knits was as good as the company's alkaline scoured ones with slightly higher K/S values. Water pollution caused by effluents of bioscouring and alkaline processes were estimated, as well as that due to the input of chemicals and enzymes. Higher BOD:COD_Cr ratios for enzymes indicated their biodegradable character. After calculation of energy consumption using a simulation program, an economic evaluation of the two processes was done on the basis of one ton production by considering the costs of chemicals and enzyme, water usage, energy consumption and waste water treatment charge.     

Significance of exploiting non-living biomaterials for the biosorption of wastewater pollutants

Industrial effluents from various sectors have become a matter of major environmental concern. The treatment of wastewater in recent year plays a significant role in order to remove the pollutants and to safeguard the water resource. The conventional wastewater treatment is considered costlier and associated with problem of sludge generation. Biosorption methods are considered as the potential solution due to their economical efficiency, good adsorption capacity and eco-friendliness. In this review, an extensive list of biosorbents from algae, bacteria, fungi and agricultural byproducts have been compiled. The suitability of biosorbents towards the eradication of heavy metals, textile dyes and phenolic compounds were highlighted. It is evident from the literature survey of recently published research articles that the biosorbents have demonstrated outstanding removal potential towards the wastewater pollutants. Therefore, biosorbents from the source of dead microbial and agricultural byproduct can be viable alternatives to activated carbon for the wastewater treatment.     

An integrated process for the treatment of CETP wastewater using coagulation, anaerobic and aerobic process

The aim of this study was to treat the wastewater collected from equalization tank of Common Effluent Treatment Plant (CETP), which was a mixture of waste coming from 525 small-scale industries manufacturing textile and dyestuff intermediate, pigments and pharmaceuticals. Initially a pretreatment using ferric chloride and lime was carried out to increase the biodegradability (BOD(5)/COD) of the effluent, which showed color removal of 74% and COD reduction of 75% at a concentration of 10 and 4 g/L. respectively. The biological treatment system using anaerobic fixed film reactor was investigated as secondary treatment. A mixture of bacterial consortium DMAB and cowdung slurry was used for the formation of biofilm. The effect of hydraulic retention time (HRT) and organic loading rate (OLR) on the efficiency of treatment of anaerobic reactor was analysed. Subsequent aerobic treatment after anaerobic step using aerobic culture Pseudomonas aeroginosa helped in further removal of COD and color. Formation of aromatic amines during anaerobic treatment was mineralized by sequential aerobic treatment.