Average COD Removal Efficiency Research Articles

High effective to remove nitrogen process in abattoir wastewater treatment

A new method of membrane sequencing batch reactor (MSBR) process in abattoir wastewater treatment is given. With nitrification and denitrification bacterium, it is effective to remove nitrogen. At the same time, the whole system can be autocontrolled and do not add any drugs or bacteriums again after it runs. The experimental results show that the quality of abattoir wastewater can attain to the national requirements of the first grade of integrated wastewater discharge standard (GB 8978 - 1996). About 45–65% of the solids or approximately 30–40% of the biological oxygen demand (BOD) load can be separated by pre-treatment screening and sedimentation. MSBR systems are lagoon, membrane sequencing batch reactor (MSBR), biological treatment and membrane filter (MF) processes. Abattoir wastewater is well suited to MSBR treatment because it is high in organic compounds. Typical reductions of up to 98% BOD, 93% SS, 98% COD, 95% NH 3-N and 95% lipin are approved. Wastewater in abattoirs can be reduced by membrane filtration which can produce recyclable water. Total COD can be reduced below 100 mg/L. The performances of both sequencing batch reactor (SBR) process and membrane sequencing batch reactor (MSBR) process operating simultaneously under the same condition to treat abattoir wastewater were examined. Conventional SBR treatment average COD removal efficiencies are of 85–90%. MSBR average COD removal efficiencies are of 98%. The result show that MSBR process has better treatment effect and is easier to operate and manage compared with SBR process. MSBR is a new method of abattoir wastewater treatment and has a broad prospects.

Treatment of slightly polluted wastewater in an oil refinery using a biological aerated filter process

The slightly polluted wastewater from oil refinery contains some COD, oil pollutants and suspended solids (SS). A small-scale fixed film biological aerated filter (BAF) process was used to treat the wastewater. The influences of hydraulic retention time (HRT), air/water volume flow ratio and backwashing cycle on treatment efficiencies were investigated. The wastewater was treated by the BAF process under optimal conditions: the HRT of 1.0 h, the air/water volume flow ratio of about 5:1 and the backwashing cycle of every 4–7 days. The results showed that the average removal efficiency of COD, oil pollutants and SS was 84.5%, 94.0% and 83.4%, respectively. And the average effluent concentration of COD, oil pollutants and SS was 12.5, 0.27, 14.5 mg·L−1, respectively. The experimental results demonstrated that the BAF process is a suitable and highly efficient method to treat the wastewater.

Removal of nitrogen from wastewater for reusing to boiler feed-water by an anaerobic/aerobic/membrane bioreactor

Abstract The innovative process anaerobic/aerobic/membrane bioreactor (A/O/MBR) was developed to enhance pre-denitrification without the energy consumption of the recirculation pump for reusing wastewater to boiler feed-water. The performance of this bioreactor was investigated. Firstly, the septic tank wastewater with low ratio of COD/TN was disposed by a dynamic membrane bioreactor (DMBR). It was found that, although the high concentration of NO 2 − –N in the effluent implied the potential ability of DMBR to realize shortcut nitrification and denitrification, the effluent of single DMBR was difficult to reach the criteria of reusing to boiler feed-water. Then, the process A/O/DMBR in disposing the septic tank wastewater was studied. The results indicated that this process not only accomplished the removal of 91.5% COD, 90.3% NH 4 + –N and 60.2% TN, but also successfully realized pre-denitrification without additional recirculation pump. At last, based on the A/O/DMBR, a pilot plant A/O/MBR was built to dispose the municipal raw sewage. In the stable operation period, the average removal efficiencies for COD, NH 4 + –N, TP and turbidity reached 90%, 95%, 70% and 99%, respectively. During the tested HRT run of 9.0 h, the effluent of COD, NH 4 + –N, TP and turbidity was about 10 mg/L, 3 mg/L, below 1 mg/L and 1.2 NTU, respectively, which reached the criteria of the boiler feed-water in China.

Treatment of jean-wash wastewater by combined coagulation, hydrolysis/acidification and Fenton oxidation

Performance of a full-scale combined treatment plant for jean-wash wastewater (JWW) was investigated. The combined process consisted of chemical coagulation, hydrolysis/acidification and Fenton oxidation. Chemical coagulation treatment with polymeric ferric sulfate (PFS)/lime alone proved to be effective in removing the COD (>70%) and part of the color (>50%) from the JWW. Fenton oxidation combined with hydrolysis/acidification as pretreatment offered a noticeable BOD removal efficiency. The average removal efficiencies for COD, BOD, SS, color and aromatic compounds of the combined process were about 95%, 94%, 97%, 95% and 90%, respectively, with the average effluent quality of COD 58 mg/L, BOD 19 mg/L, SS 4 mg/L and color 15(multiple), consistent with the national discharge limits for textile wastewater. The result indicated that the combined procedure could offer an attractive solution for JWW treatment with considerable synergistic advantages.

Treatment of Catalyst Wastewater in a Three-Phase Flow Airlift Loop Bioreactor

A 12-L gas–liquid–solid three-phase flow airlift loop bioreactor, in which micro-organism immobilization replaced the activated sludge, was used for the nitrifying treatment of the original effluent from Catalyst Complex of Qilu Petrochemical Corp. of SINOPEC, Zibo City, Shandong Province, P.R. China. The original wastewater contained a high strength NH4–N of up to 2,437 mg L−1 and solution electrical conductivity (EC) of nearly 22,000 μScm−1 . The influences of temperature, pH value, superficial gas velocity (ug) and hydraulic residence time (HRT) on the reductions of COD and NH4–N were investigated and discussed, respectively. The optimum operation condition was obtained as temperature 30–35°C, pH value 7.0–7.5, ug 10 mm s−1 , and HRT 15 h at the solid hold-up εs up to 50%. Under this optimum operation condition, the average removal efficiencies of COD and NH4 –N were higher than 85 and 99%, respectively, corresponding to the effluent COD, 25 mg L−1 and NH4 –N, 15 mg L−1 , which was in compliance with the national primary discharge standard of P. R. China as COD ≤ 100 mg L−1 and NH4-N ≤ 15 mg L−1 (GB 8978–1996). Additionally, the radial and axial positions in the reactor showed little influence on the local profiles of COD and NH4 –N.

A high loading overland flow system: Impacts on soil characteristics, grass constituents, yields and nutrient removal

The objectives of this paper are to determine effects of different grass species and their harvests on pollutant removal, elucidate impacts on soil characteristics and grass constituents, observe grass yield and quantify nutrient uptake by vegetation in an overland flow system (OLFS). Polluted creek water was applied to eight channels in the OLFS, which were planted with Paragrass, Nilegrass, Cattail, and Vetiver, with each two channels being randomly planted with a given grass species. The grass in one channel was harvested while that in the other channel was not. At a high rate of 27.8 m d(-1) hydraulic loading, the removal efficiencies of conventional pollutants such as BOD, COD, suspended solids (SS), and total coliforms in wastewater are not affected by the type of the grasses species, but those of nitrogen and phosphorus are affected by different species. Overall average removal efficiencies of BOD, COD, SS, ammonia, total nitrogen, total phosphorus and total coliforms through the OLFS are 42%, 48%, 78%, 47%, 40%, 33% and 89%, respectively. The concentration of nitrate, however, increases due to nitrification. Soil characteristics in OLFS have been changed significantly; specific conductivity, organic matter, exchangeable magnesium, extractable copper and zinc in soils all increase with time while pHs decrease. During the winter season, there is a significant accumulation of nitrate in grass with the subsequent reduction during the active growing season (Spring). The contents of nitrate and phosphorus in grass tissue are higher than those of grass in general pastureland, probably due to nutrient luxury uptake by grass. The overall grass yield, growth rate and nutrient uptake are quantified and implication of such high rate OLFS discussed.

Evaluation of a upflow anaerobic sludge blanket reactor with partial recirculation of effluent used to treat wastewaters from pulp and paper plants

The main purpose of this study was to evaluate the performance of a UASB reactor treating diluted black liquor from a Kraft pulp mill, which simulates an unbleached Kraft plant wastewater, under different operational conditions, including partial recycling of the effluent. The reactor’s performance was evaluated from the standpoint of COD, pH, volatile acid concentration, alkalinity, concentration of methane in the biogas, and microbiological examinations of the sludge. Without recirculation the reduction of the HRT from 36 to 30 h did not significantly affect the average COD removal efficiency. The parameter displaying the greatest variation was the average concentration of effluent volatile acids, which increased by 16%. With recirculation the reduction of the HRT from 30 to 24 h increased the average COD removal efficiency from 75% to 78%. In this case, the average effluent alkalinity also showed an increase. The use of partial recirculation of the effluent did not improve significantly the COD removal under the operational conditions tested in this work, but it was possible to operate the reactor with lower hydraulic retention time without disintegration of the granules.

An innovative constructed wetland system for small stream water restoration

The newly designed wetland system for the restoration of polluted stream water combines a surface and subsurface flow. It is composed of two wetlands connected in series by the flow shifter in the middle of the constructed wetland (CW) system. The flow shifter, which converts the flow direction of a surface and subsurface within the system, was able to enhance the treatability of organic contaminants and total nitrogen (TN) via nitrification and denitrification. In this system, the suspended solids (SS) and total phosphorus (TP) removal efficiencies were considerably improved by the yellow-soil media and the flow shifter. Untreated SS and TP in an upper layer of the former wetland could be eliminated in the following wetland by filtration, precipitation and adsorption onto the yellow-soil media while they flowed into a lower layer of the latter one via the shifter. At a hydraulic loading rate (HLR) and hydraulic residence time (HRT) of 222 cm/day and 5.02 hr, respectively, the average removal efficiencies of COD and TN were 63.4 and 48%, respectively, during the summer period. These values are 2 to 4 times higher than those efficiencies from the previous experimental period without the shifter.

A pilot study on a step-feeding anoxic/oxic activated sludge system

A four stage pilot plant of step-feed biological nutrient removal (BNR) was employed to investigate reactor performance and process stability. The results obtained showed that step-feed BNR is efficient and cost-effective for nitrogen and carbonaceous removal from municipal wastewater. The total average removal efficiencies of COD, NH3-N, TN and TP could reach as high as 89.5, 97.8, 73 and 75%, respectively, with 50% of return activated sludge (RAS), 9 h of hydraulic retention time (HRT) and 20 d of sludge retention time (SRT). Step-feed BNR is an alternative and effective technology of nutrient removal for municipal wastewater treatment.

Combined treatment of landfill leachate with fecal supernatant in sequencing batch reactor

A laboratory-scale sequencing batch reactor (SBR) is used to treat landfill leachate containing high concentration of ammonium nitrogen with municipal fecal supernatant. The SBR system is operated in the following sequential phases: fill period, anoxic period, aeration period, settling period, decant and idle period. The results indicated that the average removal efficiencies of COD, BOD(5), TN,NH(4)(+)-N were 93.76%, 98.28%, 84.74% and 99.21%, respectively. The average sludge removal loading rates of COD, BOD(5), TN and NH(4)(+)-N were 0.24 kg/(kg SS.d), 0.08 kg/(kg SS.d), 0.04 kg/(kg SS.d) and 0.036 kg/(kg SS.d), respectively. Highly effective simultaneous nitrification and denitrification was achieved in the SBR system. The ratio of nitrification and denitrification was 99% and 84%, respectively. There was partial NO(2)(-) denitrification in the system.

Anaerobic stabilisation of sludge produced during municipal wastewater treatment by electrocoagulation

Anaerobic digestion of sludge from small electrocoagulation wastewater treatment plant (SEWWTP) is described. The sludge for digestion (SEWWTP sludge) was taken from pilot-scale SEWWTP with the capacity of about 200-population equivalent (25 m 3 of municipal wastewater per day). Due to the technology of wastewater treatment, the characteristics of SEWWTP sludge was different from sludge produced in conventional mechanical–biological wastewater treatment plant. Therefore, experiments were focused on possibilities of anaerobic sludge digestion and determination of conditions and parameters (amount and quality of the sludge, biogas production, etc.). Average COD removal efficiency in the pilot-scale SEWWTP exceeded 80%. Organic content of excess sludge (volatile suspended solids (VSS)) was in the range of 52.1–59.2% (these values are much lower compared to VSS content in raw sludge from conventional municipal wastewater treatment plant, where VSS is about 75%). Biogas production from anaerobic digestion of SEWWTP sludge was approximately three times lower compared to standard production in conventional municipal wastewater treatment plant. Low pH (6.5–6.7), high concentration of iron (up to 1400 mg/L) and aluminium (up to 1300 mg/L) and very low (almost zero) concentration of dissolved phosphorus in sludge water were the main factors limiting the rate of anaerobic processes. Based on these results, anaerobic digestion of SEWWTP sludge was not recommended as an appropriate stabilisation method.

Optimization of operational factors of a membrance bioreactor with gravity drain

A new membrane bioreactor with gravity drain for municipal wastewater treatment was tested and its operational factors were investigated in this study. These factors include pressure head, MLSS, aeration intensity (an air flow rate per unit floor area) and temperature. Results of batch experiments showed that a critical pressure head of the MBR was 0.85-1.5 m-H2O. At a pressure head of 0.85 m-H2O, statistical analysis of batch experiments showed that aeration intensity significantly affected membrane flux, and the MLSS had no impact on membrane flux under a temperature of 22.0 +/- 1.0 degrees C. Results of the long-term continuous experiment showed that temperature significantly affected membrane flux. The impact of temperature on membrane flux in this case was about 4-10 times of that analyzed by using a classical cake layer model. During this experiment, the average removal efficiencies of COD, BOD5 and NH4+-N were over 85%, 97% and 94%, respectively.

Evaluation of the microbial diversity in an UASB reactor treating wastewater from an unbleached pulp plant

The microbial community in the sludge blanket of a bench scale upflow anaerobic sludge blanket (UASB) reactor with partial recirculation of the effluent, treating wastewater from an unbleached pulp plant, was evaluated by means of the small subunit (SSU) rRNA gene amplified by polymerase chain reaction (PCR) and separated using the denaturing gradient gel electrophoresis (DGGE) technique. The average COD removal efficiency was 80–86% without recirculation and 75–78% with recirculation. Partial recirculation of the effluent did not alter the predominant population in the reactor under the conditions studied. A microscopic analysis revealed the presence of a variety of cellular morphologies. The DGGE results revealed that the structure of the microbial community was found to be complex and most of the population was similar, persisting throughout the experimental period. The microbial community of the Domain Bacteria was more sensitive to operational changes than the Domain Archaea.

Effect of organic loading rate on a wastewater treatment process combining moving bed biofilm and membrane reactors

The effect of moving bed biofilm reactor (MBBR) loading rate on membrane fouling rate was studied in two parallel units combining MBBR and membrane reactor. Hollow fiber membranes with molecular weight cut-off of 30 kD were used. The HRTs of the MBBRs varied from 45 min to 4 h and the COD loading rates ranged from 4.1 to 26.6 g COD m(-2) d(-1). The trans-membrane pressure (TMP) was very sensitive to fluxes for the used membranes and the experiments were carried out at relatively low fluxes (3.3-5.6 l m(-2) h(-1)). Beside the test with the highest flux, there were no consistent differences in fouling rate between the low- and high-rate reactors. Also, the removal efficiencies were quite similar in both systems. The average COD removal efficiencies in the total process were 87% at 3-4 h HRT and 83% at 0.75-1 h HRT. At high loading rates, there was a shift in particle size distribution towards smaller particles in the MBBR effluents. However, 79-81% of the COD was in particles that were separated by membranes, explaining the relatively small differences in the removal efficiencies at different loading rates. The COD fractionation also indicated that the choice of membrane pore size within the range of 30 kD to 0.1 microm has very small effect on the COD removal in the MBBR/membrane process, especially with low-rate MBBRs.

Treatment of winery wastewater in a full-scale fixed bed biofilm reactor

The treatment of winery wastewater was performed at full-scale applying a two-stage fixed bed biofilm reactor (FBBR) system for the discharge in the sewerage. The results of the first year of operation at the full-scale plant are presented. Values of removed organic loads and effluent concentrations were interpreted on the basis of the COD fractionation of influent wastewater assessed through respirometric tests. The average removal efficiency of total COD was 91 %. It was not possible to reach an higher efficiency because of the unbiodegradable soluble fraction of COD (about 10% of total COD on average during the whole year), that cannot be removed by biological process or settling. Due to the high empty space offered by the plastic carriers, FBBRs did not require backwashing during the seasonal operationing period of the plant (September-March). In comparison with other treatment systems the FBBR configuration allows one to ensure a simple management, to obtain high efficiency also in the case of higher fluctuations of flow and loads and to guarantee a good settleability of the sludge, without bulking problems.

UASB performance for bleached and unbleached kraft pulp synthetic wastewater treatment

This paper presents the performance of two bench scale Upflow Anaerobic Sludge Blanket reactors (UASB) used for the treatment of synthetic substrates that simulate bleached and unbleached cellulose pulp plant wastewaters. The control reactor was fed with diluted black liquor and the treatment reactor with the same substrate plus a mixture of chlorinated organics. The total concentration of the chlorinated compounds was gradually increased from 2.5 mg l −1 to 15.0 mg l −1. The average COD removal efficiency during the last phase of the experiment was 81% in the control reactor and 76% in the treatment reactor. These results indicate the capability of UASB reactors to treat this kind of wastewater and the low impact of the chlorinated organics on COD removal efficiency. The minimum overall chlorinated organics removal efficiency was 71% and the maximum was 99.7%. The experiment indicates that under the conditions used in this research the presence of chlorinated organics does not negatively impact the treatment process.

Nutrient removal by the integrated use of high rate algal ponds and macrophyte systems in China

High Rate Algal Ponds (HRAP) were operated at pilot scale to investigate the performance of HRAP under the temperate climate conditions of Shanghai, China. The results indicated that the HRAP gave good efficiency for nutrient removal, especially during summer. With a retention time of 4 or 8d according to the season, the annual average removal efficiencies for COD, NH4-N and PO4-P were 50%, 87% and 40%, respectively. The multi-factor linear models showed the relationships between nutrient removal efficiency and influencing factors. Using a macrophyte pond to separate algae from HRAP can achieve concentrations of COD, TP and TKN in the effluent at around 50 mg/L, 1.5 mg/L and 5 mg/L respectively.

Nitrifying Treatment of Wastewater from Fertilizer Production in a Three‐Phase Flow Airlift Loop Bioreactor

AbstractA 12‐L gas‐liquid‐solid three‐phase flow airlift loop bioreactor, in which biological membranes replace the activated sludge, was used in the nitrifying treatment of a real effluent in a Nanjing chemical fertilizer plant. The influences of temperature, pH, air flow rate and HRT on ammonia nitrogen reduction were investigated and discussed. The optimum operating conditions, such as temperature of 30–35 °C, pH value of 7–8, air influx of 0.3 m3/h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH4‐N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH4‐N < 5 mg/L, which is far below the primary discharge standard for the chemical fertilizer industry of P.R. China – COD < 150 mg/L and NH4‐N < 60 mg/L (GWPB4–1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH4‐N.

Nitrifying Treatment of Wastewater from Fertilizer Production in a Three‐Phase Flow Airlift Loop Bioreactor

A 12-L gas-liquid-solid three-phase flow airlift loop bioreactor, in which biological membranes replace the activated sludge, was used in the nitrifying treatment of a real effluent in a Nanjing chemical fertilizer plant. The influences of temperature, pH, air flow rate and HRTon ammonia nitrogen reduction were investigated and discussed. The optimum operating conditions, such as temperature of 30-35 °C, pH value of 7-8, air influx of 0.3 m 3 /h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH 4 -N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH 4 -N < 5 mg/L, which is far below the primary discharge standard for the chemical fertilizer industry of P.R. China - COD < 150 mg/L and NH 4 -N < 60 mg/L (GWPB4-1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH 4 -N.

The denitrification of nitrate contained wastewater in a gas–liquid–solid three-phase flow airlift loop bioreactor

Denitrification of nitrified effluent with high concentration of nitrate, low COD in fertilizer plant was carried out in a 12-l gas–liquid–solid three-phase flow airlift loop bioreactor, in which biological membrane replace the activated sludge. The influences of pH, temperature, C/N ratio, gas–liquid ratio and HRT on the removal of nitrate-nitrogen were investigated and discussed. The optimum operation conditions were obtained as pH value of 6.5–7.5, temperature of 20–35 °C, C/N ratio of 0.95–1, gas–liquid ratio of 62.5 and HRT of 2.5 h. Under optimum operation conditions, the average removal efficiencies of COD and NO x –N are higher than 93 and 96%, corresponding to the effluent concentrate of nitrate <20 mg/l and COD <40 mg/l. The radial and axial positions have little influence on the local profiles of COD and NO x –N.