Removal Of Residual COD Research Articles

Water recovery and on-site reuse of laundry wastewater by a facile and cost-effective system: Combined biological and advanced oxidation process

Combined biological and physicochemical process was selected for treatment of laundry wastewater. The results show that after microbial adaptation, almost 91% of COD was removed at food to microorganism (F/M) ratio of 0.12 gBOD/gMLSS·d. Dehydrogenase activity of the biomass showed an increasing trend and finally reached 3.8 μgTFgbiomass.d corresponding to the highest process performance. 16SrRNA fragment and phylogenetic analysis identified Pseudomonas pharmacofabricae and Bacillus spp. as the dominant bacteria. The effluent of the biological process was then injected into the UV/O3 process for complete removal of residual COD and detergent. Finally, microfiltration and ultrafiltration were used to remove any remaining suspended solids. The operating cost analysis showed that 0.65 €/m3 treated wastewater is required for treatment of the laundry wastewater. Accordingly, the suggested combination of the biological and physicochemical process could be a promising and highly efficient process for treatment and reuse of laundry wastewater.

Material inter-recycling for advanced nitrogen and residual COD removal from bio-treated coking wastewater through autotrophic denitrification

For wastewaters containing high strength sulfide and nitrogen (e.g. coking wastewater), sulfide might be precipitated and recovered using ferrous salt. This study systematically investigated the feasibility of recovered and precipitated FeS (comparing to commercial FeS minerals) to support autotrophic denitrification for advance nitrogen removal from bio-treated coking wastewater in fluidized bed reactors. The reactor with precipitated FeS could achieve simultaneous removal of NO3−-N and inert COD with high efficiencies of around 96.3% and 30.5%, at NO3−-N and COD loading rates of 4.18 mg·L−1·h−1 and 8.06 mg·L−1·h−1, respectively. Whereas, the performance of commercial FeS reduced gradually and irreversibly after two days, which became completely ineffective after 40 days. Thiobacillus and Rhodanobacter dominated the biomass, which played a key role in the FeS-based denitrification process. This material inter-recycling concept benefits an advance and more sustainable treatment of wastewaters with high strength sulfide and nitrogen.

Anoxic–aerobic SBR system for nitrate, phosphate and COD removal from high-strength wastewater and diversity study of microbial communities

Anoxic–aerobic sequencing batch reactor (SBR) system was operated for 180 days (under ambient temperature, 20 days SRT, 24h HRT, influent COD/nitrate: 4 and COD/phosphate: 137) to treat a high strength wastewater (1000mg/L nitrate and 4000mg/L COD). The unique aspect was elimination of anaerobic cycle due to availability of nitrate (NO3) and oxygen as electron acceptors in anoxic and aerobic phases respectively. Simultaneous removal of nitrate (98%), phosphate (86%), and COD (72%) was achieved in anoxic phase. The subsequent aerobic phase experienced 26% of residual COD removal along with phosphate release (∼3.4mg/L), reducing the overall P-removal to 76%. A long anoxic phase (18h) could sustain denitrifying dephosphatation with less MLSS generation. Pyrosequencing data were analyzed through Ribosomal database project (RDP) and DECIPHER while diversity of sampling was analyzed using Chao1 and Shannon index. Rarefaction curve reflected adequacy of sampling for total species diversity study. Overall analysis revealed Proteobacteria, Alphaproteobacteria, Rhodobacterales, Rhodobacteraceae and Paracoccous as the prominent phylum, class, order, family, and genus respectively.Surplus electron donor and acceptor in anoxic phase (feasting) were advantageous for enrichment of DNPAOs over OHOs while nitrate exhaustion in the aerobic phase provided adequate fasting condition to maintain DNPAOs dominance. Low specific denitrification rate values in comparison to other heterotrophs, also supported enrichment of denitrifying phosphate accumulating organisms (DNPAOs) in the anoxic–aerobic sequencing batch reactor. Diverse micro flora ensured robustness and performance stability in high strength wastewater.

Recovery of residual soluble protein by two-step precipitation process with concomitant COD reduction from the yeast-cultivated cheese whey

The present study was conducted to recover the residual soluble protein after cultivation of yeast (K. marxianus) in cheese whey. Cheese whey continuous fermentation with cell recycle system was carried out at 40°C and pH 3.5. The yeast biomass was separated from the fermented broth by centrifugation and residual soluble protein from fermented whey supernatant was precipitated by heat treatment (at 100°C, pH 4.5 and 10min incubation). The maximum soluble protein recovery up to 53% was achieved at pH 4.5 with 54% residual COD removal. However, gravity sedimentable precipitates were obtained at pH 3.5 with 47% protein recovery. Therefore, the reactor (scale up) study was conducted at pH 3.5 with agitation, which resulted in 68% of residual soluble protein recovery and simultaneously residual COD removal of 62%. Further precipitation/coagulation of soluble protein was also evaluated using carboxymethylcellulose (CMC) and then two precipitation (thermal followed by CMC precipitation) processes were combined to increase the protein precipitation, which finally reached up to 81% of total soluble protein recovery from the supernatant. This optimized process could be applied to recover the residual protein left after fermentation of cheese whey without centrifugation.

Removal of Residual COD in Biologically Treated Paper-Mill Effluent and Degradation of Lignin Using Nonthermal Plasma Unit

This manuscript focused on the degradation behavior of lignin and the reduction of residual COD in the biologically treated paper-mill effluent by means of ionized gas from nonthermal plasma unit. The removal efficiencies of COD, lignin, and color after treated with ionized gas were over 95, 93, and 97%, respectively. It has been found that the degradation of aromatic ring has been proved by FTIR, 1H NMR and UV spectra. The degradation of lignin through ionized gas was accompanied with the increase of and the decrease in pH. The results show that the residual COD in the biologically treated paper-mill effluent contains NBD matter with aromatic ring compounds. Also NBD organic matter such as aromatic ring in effluent treated with ionized gas was degraded. The residual COD declined by 60% at the ionized gas flow rate 5 L/min and HRT 30 min.

Fenton’s pre-treatment of mature landfill leachate

The aim of this study was to check the effectiveness of the Fenton’s reagent (Fe 2+ + H 2O 2 + H +) for the pre-treatment of a municipal landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD 5/COD ratio, up to a value compatible with biological treatment. The leachate came from a municipal sanitary landfill located in southern Italy and the average values of its main parameters were: pH=8.2; COD=10 540 mg l −1; BOD 5=2300 mg l −1; TOC=3900 mg l −1; NH 4-N=5210 mg l −1; conductivity=45350 μS cm −1; alkalinity=21 470 mg l −1 CaCO 3. The effect of initial pH value on the pre-treatment effectiveness was evaluated by titrating the amount of acidic by-products formed. The extent of leachate oxidation was monitored and controlled by both pH and redox potential measurements. The best operational conditions for achieving the desired goal (i.e., BOD 5/COD ⩾ 0.5) resulted: Fe 2+=275 mg l −1; H 2O 2=3300 mg l −1; initial pH=3; reaction time=2 h. At the end of the Fenton’s pre-treatment, in order to permit a subsequent biological treatment, residual ferric ions were removed increasing the pH up to 8.5 by adding 3 g l −1 of Ca(OH) 2 and 3 mg l −1 of a cationic polyelectrolyte, the latter as an aid to coagulation. This final step also resulted in a further modest removal of residual COD due to co-precipitation phenomena.

Advanced Oxidation of Biologically Pretreated Baker's Yeast Industry Effluents for High Recalcitrant COD and Color Removal

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, ozonation with hydrogen peroxide and Fenton's processes for decolorization and residual COD removal of biologically pretreated baker's yeast industry (BYI) effluents. Baker's yeast industry effluents characterizing with high COD, TKN, dark color, and non-biodegradable organic pollutants. The batch tests were performed to determine the optimum operating conditions including pH, O3, H2O2, and FeSO4 dosages, molar ratio of Fe2+/H2O2 and reaction time. It was noticed that H2O2 significantly reduced the reaction times for the same ozone dosages; however, COD and color removals were not remarkable. In the Fenton's oxidation studies, the removal efficiencies of COD and color for 30 min reaction time for three different types of BYI effluents were found about 86 and 92%, respectively. Experimental results of the presented study have clearly indicated that the Fenton's oxidation technology is capable to fate almost all parts of the organics which consist of both soluble initial and microbial inert fractions of COD for baker's yeast effluents. Effluents from the Fenton's oxidation process can satisfy effluent standards for COD and color in general.

5556535 Filtration system for recycling water used in a car wash : Van Der Est N Ambacht, Netherlands assigned to Micro Tec B V

Combined biological and physicochemical process was selected for treatment of laundry wastewater. The results show that after microbial adaptation, almost 91% of COD was removed at food to microorganism (F/M) ratio of 0.12 gBOD/gMLSS·d. Dehydrogenase activity of the biomass showed an increasing trend and finally reached 3.8 μgTFgbiomass.d corresponding to the highest process performance. 16SrRNA fragment and phylogenetic analysis identified Pseudomonas pharmacofabricae and Bacillus spp. as the dominant bacteria. The effluent of the biological process was then injected into the UV/O3 process for complete removal of residual COD and detergent. Finally, microfiltration and ultrafiltration were used to remove any remaining suspended solids. The operating cost analysis showed that 0.65 €/m3 treated wastewater is required for treatment of the laundry wastewater. Accordingly, the suggested combination of the biological and physicochemical process could be a promising and highly efficient process for treatment and reuse of laundry wastewater.

Combined organic carbon and complete nitrogen removal using anaerobic and aerobic upflow filters

Two laboratory upflow aerobic and anaerobic filters fed with synthetic wastewaters were used to study firstly the effects of aeration rate on the nitrification of anaerobically pre-treated effluents and secondly the effects of recycle-to-influent ratios on methane production rate, denitrification and nitrification performances of a combined aerobic and anaerobic wastewater treatment process. Nitrification of anaerobically pre-treated effluent was accompanied by aerobic post-treatment for residual COD removal. A comparison of nitrification performances using autotrophic medium and anaerobically pre-treated effluents (containing 1203 mg COD 1−1) with the same ammonia nitrogen concentration of about 300 mg NH4-N 1−1 showed that 3% of added ammonia nitrogen was assimilated by autotrophic nitrifiers during nitrification of the autotrophic medium while up to 30% was assimilated by both nitrifiers and heterotrophs during organic carbon removal and nitrification of anaerobically pre-treated effluent. Furthermore, it was suspected that significant nitrogen loss through denitrification occured in the aerobic filter especially at low aeration rates. In the study of the combined aerobic-anaerobic system, maximum ammonia nitrogen removal of 70% through denitrification was obtained at recycle-to-influent ratios of 4 and 5. COD removal efficiency in the anaerobic filter decreased from 77 to 60% for recycle-to-influent ratios of zero to 5. Overall COD removal efficiency of the entire system was constant at about 99% due to heterotrophic COD removal in the aerobic filter.

Treatment of Perfume Manufacturing Wastewaters by Co-Metabolism with an Alcohol Substrate

A fragrance manufacturing wastewater is to be treated using a flowsheet which includes combined equalization and organics stripping, biological treatment followed by catalyzed chemical oxidation and waste sludge handling. Two biological processes were investigated for comparison. The first was a conventional extended aeration process, using a bench-scale reactor; the second was a cyclically operated activated sludge system batch reactor using a demonstration unit on-site. Operating parameters for generating an effluent quality of around 600 mg/L COD, through biological treatment, were established. It was found necessary to adjust the feed substrate concentration with a concentrated wastewater component to support microbial growth. The combined fragrance manufacturing waste stream was characterized by an initial COD of around 23000 mg/L. The treatment facility is required to meet a 300 mg/L COD, 175 mg/L BOD and 250 mg/L TSS effluent quality by the regulatory authorities. Satisfactory removal of residual COD to meet the discharge specification was obtained in bench tests using catalyzed chemical oxidants following biological treatment. The design intent of the full-scale facility is 38000 litres/day.