Average COD Removal Research Articles

Role of Biochar in Anaerobic Digestion Based Biorefinery for Food Waste

The effect of biochar addition on the anaerobic digestion (AD) of food waste was evaluated. From the five biochars tested, Fe, Co, Ni, and Mn were leached in very small quantities (less than 10 mg/kg), while a high amount of K (1510 and 1969 mg/kg) was leached from treated waste wood and willow tree pyrochar, respectively. AD batch experiments were performed at an inoculum:substrate ratio of 1:1, at 30 °C and under agitating conditions. The results showed that the biogas volume produced by the treatments with the brewery residue hydrochar and treated waste wood pyrochar was lower than the amount of biogas produced by the control with only food waste. The food waste supplemented with 1.5 mL of trace elements yielded the highest biogas of 588 mL/g COD (CH4 content - 48%). Furthermore, two identical upflow anaerobic sludge blanket (UASB) reactors, i.e. control reactor and biochar amended reactor, were operated at 30 °C, at organic loading rates (OLR) varying from 3.4 to 7.8 g COD/L.day. The average COD removal efficiencies of the control and the biochar-amended reactor were 47% and 77% at an OLR of 6.9-7.8 g COD/L.day, respectively. These study results clearly indicate that the type of biochar and trace elements concentration in biochar play a key role in determining the effectiveness of the biochar in enhancing biogas production from food waste.

Integration of Membrane Bioreactor and Nanofiltration for the Treatment Process of Real Hospital Wastewater in Ho Chi Minh City, Vietnam

Hospital wastewater contains pharmaceutical residues, chemicals, and pathogens that cause coloration and nourish pathogenic microorganisms. The objective of the study was to evaluate the effectiveness of a medical wastewater treatment system at Military Hospital 175 (Ho Chi Minh City, Vietnam) that combined a membrane bioreactor (MBR) system with nanofiltration (NF). The influent of the system was the wastewater discharged from the operating rooms of the hospital. The system has a capacity of 50 L/day and operates at three organic load rates (OLR) of 0.5, 1.5 and 2.5 kgCOD/m3day (COD: Chemical oxygen demand), in which each load rate operates for 40 days. The results showed that most nutritional criteria generally achieved positive results. Specifically, the average COD removal was shown to be consistently high throughout the three phases at 94%, 93.3%, and 92.7%, respectively. For removal of nitrogen, the system demonstrated efficiencies of 75%, 79%, and 83%, respectively, to three phases. The log removal value (LRV) for Escherichia coli and coliform bacteria were higher than four throughout the study period. The average removal efficiency for color and total iron was approximately 98% and 99%, respectively. The water quality after treatment, especially after NF, meets the Vietnamese standard of grade A. The arrangement in which the MBR preceded NF was also found to limit the amount of soil and solids entering subsequent treatment, which therefore improved the efficiency of NF, as demonstrated by the stability of post-NF transmembrane pressures throughout three cycles renewed by two backwashes.

Anaerobic co-digestion of industrial landfill leachate and glycerin: methanogenic potential, organic matter removal and process optimization

ABSTRACT The objective of this study was to evaluate the performance of the anaerobic co-digestion of different concentrations of industrial landfill leachate associated with crude residual glycerin, in relation to the methanogenic potential, COD removal, accumulated methane production, the effects of the factors (food/microorganism ratio and percentage of glycerin added to the leachate) and their interactions on kinetic parameters of methane production (CH4) using the modified Gompertz model. Co-digestion tests were carried out in bench scale (400 mL of useful volume) under batch mode at 30 ± 1°C during 30-day incubation of anaerobic sewage sludge as inoculum. The parameters glycerin addition to the leachate (v/v) (0%, 1.5%, 5%, 8.5% and 10%) and F/M ratio (0.3, 0.5, 1, 1.5 and 1.7) were investigated using Central Composite Rotational Design method (CCRD). The results indicated significant effect to the response variables: methanogenic potential, COD removal, accumulated production of CH4 and maximum estimated production of CH4, considering a confidence interval of 95% (p < .05). The ideal mixture of 95.13% of leachate with 4.87% of raw glycerin was obtained by desirability test to F/M of 1.61 gCOD of substrate per gVSS (volatile suspended solids) of sludge. Methanogenic potential was 0.19 LNCH4 gTVSrem −1, and the average removal of COD was 92%, resulting in accumulated production and maximum estimated production of CH4 of 74 and 80 mL, respectively. It was noted that the process of co-digestion of the industrial landfill leachate with the crude residual glycerin is promising, due to is potential of complementing and balancing organic materials, nutrients and other components that influence the biological process. Abbreviations: AN: ammoniacal nitrogen; BMP: biochemical methane potential; CCRD: central composite rotational design; COD: chemical oxygen demand; F/M ratio: food/microorganism ratio; FSS: fixed suspended solids; NTP: normal temperature and pressure; TSS: total suspended solids; TA: total alkalinity; TFS: total fixed solids; TKN: total Kjeldahl nitrogen; TP: total phosphorus; TS: total solids; TVA: total volatile acids; TVS: total volatile solids; VSS: volatile suspended solids; WWTP: wastewater treatment plant

A novel phenol and ammonia recovery process for coal gasification wastewater altering the bacterial community and increasing pollutants removal in anaerobic/anoxic/aerobic system

Coal gasification wastewater (CGWW) is a typical toxic and refractory industrial wastewater. Here, a novel phenol and ammonia recovery process (IPE) was employed for CGWW pretreatment, and the coupled system assemble by the IPE process with A2/O system (IPE-A2/O) were operated to enhance the treatment performance of CGWW. The results showed that the IPE pre-treated effluent had a higher BOD5/COD ratio and lower refractory compounds compared to a typical process (MIBK). Subsequent A2/O biological treatment indicated that the A2/O-p system (A2/O system followed IPE process) obtained a higher average COD removal of 92% compared to 87.7% of the control (A2/O-m, A2/O system followed MIBK). The GC–MS analysis suggested that the content of alkanes in the IPE-A2/O effluent was lower than that of the MIBK-A2/O. The high-throughput sequencing revealed Levilinea, Alcaligenes, Acinetobacter, Thauera and Thiobacillus were the core genera in A2/O system. The genera Alcaligenes, Acinetobacter, Thauera and Thiobacillus in the degrading consortium were enriched in the A2/O-p system, leading to increased removals of organic pollutants and TN. These results suggested that the IPE process was a feasible pretreatment method, and the coupled IPE-A2/O system was an alternative technique for treating CGWW.

Effect of the Influent C/P Ratio on the Nutrient Removal Characteristics of the SNEDPR System

This study focuses on the nitrogen (N) and phosphorus (P) removal characteristics in a simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) system at different influent C/P ratios. An extended anaerobic/low aerobic (dissolved oxygen:0.5-1.0 mg·L-1) sequencing batch reactor (SBR) fed with municipal sewage was studied by adjusting different C/P ratios (10, 15, 20, 30, and 60). The experimental results show that the proper reduction of the influent C/P ratio (C/P ratio reduced from 60 to 30) enhances the competitive advantages of phosphorus-accumulating organisms (PAOs) in the SNEDPR system. The highest phosphorus removal efficiency was achieved at a C/P ratio of 30, with the anaerobic phosphorus release rate (PRR) and aerobic phosphorus uptake rate (PUR, used as P/MLSS) reaching 3.5 mg·(g·h)-1 and 4.2 mg·(g·h)-1 respectively, and an average effluent PO43--P concentration below 0.3 mg·L-1. The percentage of PAOs contributing to the storage of endogenesis carbon (PPAO, An) reached 88.1%. However, a poor phosphorus removal performance was observed with further reduction of the influent C/P ratios to 10; both the PO43--P removal efficiency and PPAO, An decreased from 38.1% and 82.4% to 3.1% and 5.3%, respectively. The PRR and PUR were 0.2 mg·(g·h)-1 and 0.24 mg·(g·h)-1, respectively. The COD removal performance was not affected by the decreasing influent C/P ratios; the average COD removal efficiency stabilized at 85%. In addition, the nitrification performance became worse with decreasing C/P ratios (from 60 to 20) because the effluent NH4+-N and NO2--N concentrations increased from 0 and 6.9 mg·L-1 to 5.1 mg·L-1 and 16.2 mg·L-1, respectively. The nitrificaton performance recovered when the C/P ratios further decreased to 10, but the nitrite accumulation was disturbed as both the effluent NH4+-N and NO2--N concentrations reduced to 0. The effluent NO3--N concentration increased from 0.08 mg·L-1 to 14.1 mg·L-1. The SNED efficiency first decreased from 62.1% to 36.4% and then increased to 56.4%. The advantageous competition of glycogen accumulating organisms (GAOs) improved when the influent C/P ratio was lower than 15. The enhancement of the endogenous denitrification ability of GAOs might explain the recovery denitrification performance of the system when the influent C/P ratios decreased from 20 to 10.

Effect of silver nanoparticles on an integrated fixed-film activated sludge–sequencing batch reactor: Performance and community structure

The effects of silver nanoparticles (AgNPs) on reactor performance, extracellular polymeric substances composition and microbial community structure and function in integrated fixed-film activated sludge–sequencing batch reactors (IFAS–SBRs) were investigated. Results showed that the addition of AgNPs from 0.1 to 10 mg/L exhibited no significant effects on nutrient removal. The average overall removal of COD, NH4+–N and PO43−–P was 96.6%, 99.9% and 98.8%, respectively. The introduction of AgNPs caused an increase in extracellular polymeric substances content for the sludge and biofilm of IFAS–SBRs. The release of Ag+ from AgNPs and lactate dehydrogenase test implied the low toxicity of AgNPs to IFAS–SBRs. High-throughput sequencing revealed that microbial community structure showed significant shifts at phylum and genus levels after long-term exposure to AgNPs, but core functional groups responsible for nutrient removal remained at high abundance. Bacterial function prediction indicated that the metabolic categories showed no significant shifts under AgNPs stress, therefore good process performance could still be achieved.

Influence of amoxicillin after pre-treatment on the extracellular polymeric substances and microbial community of anaerobic granular sludge

A combined process coupling a Fe3O4 nanoparticles (Fe3O4 NPs) heterogeneous Fenton-like reaction and an anaerobic biological technology was investigated in order to effectively treat amoxicillin-containing wastewater. With the increase in the pretreatment degree, the average COD removal rate correspondingly increased from 84.8% to 92.4% using the anaerobic biological treatment, and the biodegradability and COD removal efficiency was improved by the pretreatment processes. During the process of amoxicillin degradation, hydroxyl free radicals tended to attack the lactamide, amide and pentacyclic rings of amoxicillin. In the excitation-emission matrix (EEM) spectra of soluble microbial products (SMPs), the absorption peak of humic acid gradually decreased with application of the pretreatment. The pretreatment products were more beneficial to the characteristics of anaerobic granular sludge. For the microbial community structure, the proportion of Methanothrix and Clostridia increased with addition the heterogeneous Fenton-like pretreatment, which favored conversion of organic contaminants to volatile fatty acids and biogas.

Nutrient removal from high ammonium swine wastewater in upflow microaerobic biofilm reactor suffered high hydraulic load

To understand the ability of an upflow microaerobic biofilm reactor (UMBR) to remove nutrient from manure-free swine wastewater rich in NH4+ with a COD/TN ratio less than 1.00, effect of hydraulic loading rate (HLR) on the microaerobic process was evaluated with a constant reflux ratio of 25 at 25 °C. The results showed that changes in HLR had a remarkable effect on the performance of the UMBR in nutrient removal from the wastewater. With the favorable HLR 3.0 m3/(m3·d) (Hydraulic Retention Time (HRT) 8 h), average removal of COD, NH4+ and TN in the microaerobic process reached 59.3%, 87.7% and 84.7%, respectively, though the COD/TN ratio was as low as 0.84. With an over HLR of 4.0 m3/(m3·d) (HRT decreased to 6 h), bad performance of the UMBR was observed with an average removal of COD, NH4+ and TN as low as 45.0%, 59.0% and 57.5%, respectively. Since the HLR was decreased to 2.4 m3/(m3·d) (HRT 10 h), the microaerobic process regained the efficiency in nutrient removal with a removal of COD, NH4+ and TN averaged 59.0%, 95.3% and 87.8%, respectively. The microaerobic condition allowed anammox bacteria, ammonia-oxidizing bacteria and archaea, nitrite-oxidizing bacteria and denitrifiers to all thrive in the UMBR, resulting in the efficient synchronous removal of organic carbon and nitrogen. As the dominant approach to nitrogen removal, anaerobic ammonium oxidation (anammox) pathway contributing to the TN removal in the microaerobic process exceeded 59.5% at HLR 3.0 m3/(m3·d). The results demonstrated that the UMBR can remove nitrogen and carbon from swine wastewater, with a suitable HLR.

Performance and microbial community of an expanded granular sludge bed reactor in the treatment of cephalosporin wastewater

In this study, the anaerobic treatment and microbial characteristics of high-concentration cephalosporin wastewater were studied. A pilot-scale expanded granular sludge bed (EGSB) reactor was designed to treat cephalosporin wastewater, whose diameter, height and effective volume were 0.5 m, 4.9 m, 0.92 m3, respectively. With mixed high-concentration cephalosporin wastewater and municipal wastewater as a substrate, the anaerobic reactor was started and operated 414 days. An average COD removal efficiency of 72% was achieved at an organic loading rate (OLR) of 9.96 kg COD/(m3·d), with a hydraulic retention time (HRT) of 25 h. The average methane content reached 82%. Methanobacterium and Methanomassiliicoccus were predominant archaea in the granular sludge for each of the organic loading rates, and the predominant methane-producing pathway was hydrogenotroph and methylotroph. Those results demonstrated that the EGSB reactor could treat high-concentration cephalosporin wastewater with a unique methane-producing pathway.

Fouling mitigation through maghemite particles in membrane bioreactor

In this study, there were two parallel membrane bioreactors (MBR) were operated to verify the influence of maghemite addition on membrane fouling in municipal wastewater treatment at maghemite addition of 0.54 gL−1. Mesoporous maghemite particles was prepared via hydrothermal method. The average COD removal was 95% involving in effluent with COD ranging from 12-55 mg/L. The turbidity of both MBR effluent values ranged from 0.4 to 1.5 NTU. The feed and operating conditions were similar in both MBR, and COD, turbidity, TMP, flow rate, SVI, MLSS and EPS were monitored over 60-day period. Maghemite was able to adsorp the proteins and after maghemite addition, the rate of membrane fouling was decreased. Detailed studies on the effect of maghemite addition in MBR indicated that maghemite dosage of 0.54 gL−1 was able to reduce fouling in membrane bioreactors.

Characteristics of heterotrophic nitrification and aerobic denitrification bacterium Acinetobacter sp. T1 and its application for pig farm wastewater treatment

A novel heterotrophic bacterium was isolated from activated sludge of a pig farm wastewater treatment plant and identified as Acinetobacter sp. T1. It exhibited efficient heterotrophic nitrification and aerobic denitrification capability to utilize ammonium, nitrate or nitrite as the sole nitrogen source, and their removal rates were 12.08, 5.53 and 1.69 mg/L/h, respectively. Furthermore, the optimal conditions for the heterotrophic nitrification process were sodium citrate as the carbon source, C/N mass ratio of 10, pH of 8.5 and dissolved oxygen (DO) concentration of 5.1mg/L. Only trace amounts of nitrate and nitrite were observed during the process. When the aerobic tank of the A2O process of a pig farm wastewater treatment plant was inoculated with traditional activated sludge, the average removals of COD, NH4+- N and TN in the effluent were 30%, 15% and 16%, respectively, which was much lower than that of inoculated with strain T1, the increase was statistically significant, indicating a great potential of strain T1 for full-scale applications.

Enhancement of Organic Matter Removal in an Integrated Biofilm-Membrane Bioreactor Treating High-Salinity Wastewater.

High salinity can strongly inhibit microbial activity and decrease the sedimentation ability of activated sludge. The combination of biofilm and membrane bioreactor is a practical approach towards effective removal of pollutants and low fouling rate. An integrated biofilm-membrane bioreactor (BMBR) treating mustard tuber wastewater was investigated. An average COD removal efficiency of 94.81% and ammonium removal efficiency of 96.84% were achieved at an organic load of 0.5 kg COD/(m3·d). However, the reactor showed a relatively low efficiency in total nitrogen and soluble phosphorus removal due to the lack of anaerobic environment. The increase of influent organic load resulted in a performance degradation because a balance between the degradation ability and pollution has been reached. Images of scanning electron microscopy revealed that halophilic bacteria were the dominant microbe in the system that leads to a loose sludge structure and declined settling properties. It was found that membrane fouling was the consequence of the interaction of microbial activities and NaCl crystallization.

Granulation process in an expanded granular sludge blanket (EGSB) reactor for domestic sewage treatment: Impact of extracellular polymeric substances compositions and evolution of microbial population

In this study, an expanded granular sludge blanket (EGSB) reactor was used for the treatment of low-strength domestic sewage and the sludge granulation process was systematically investigated. At an optimized hydraulic retention time (HRT) of 5 h, up-flow velocity (Vup) of 1.9 m/h, and organic loading rate (OLR) of 2.16 kg COD/m3/d, the average COD removal efficiency was 71.5 ± 2.3%. Completely granular sludge can be observed after 107 d of continuous operation. Analysis of the distribution and composition of the extracellular polymeric substances (EPS) indicates that the tightly bound EPS (TB-EPS) content shows an increasing trend, while the loosely bound EPS (LB-EPS) content did not significantly alter after the granular sludge was formed. The three-dimensional excitation-emission matrix technique (3D-EEM) confirms that aromatic protein-like substances are of key importance to sludge granulation. High-throughput sequencing analysis indicates that the metabolism shifted from hydrogenotrophic (Methanobaterium) to aceticlastic methanogens (Methanosaeta) during sludge granulation.

Enhanced organics and Cu2+ removal in electroplating wastewater by bioaugmentation

With the improvement of electroplating process and products requirement, refractory organics, heavy metals or even heavy metal nanoparticles (NP) exist simultaneously in electroplating wastewater inevitably, makes electroplating wastewater treatment effluent difficult to meet the discharge standard. In order to improve the organics removal under the exposure of CuO NP, strains (designated as L1–L5) that have both organics degradation and Cu2+ tolerance capacities were isolated and employed in the electroplating wastewater bioaugmentation treatment using a hydrolytic/anoxic/oxic-membrane bioreactor. The Cu2+ adsorption process followed pseudo-second order kinetics and the isotherms fit well to Langmuir isotherm model. L2, L3 and L4 showed higher Cu2+ adsorption capacity than that of L1 and L5. Under the optimal condition, the maximum Cu2+ adsorption capacity of L2, L3 and L4 was 34.15, 45.68 and 26.72 mg g−1, respectively. Their average COD removal efficiency achieved 65.7 ± 10.9%, 61.5 ± 6.7% and 71.6 ± 6.0%, respectively. The three isolates were used to construct consortia with the inoculum concentration of 400 mg L−1. One-time and repeated inoculations were evaluated to find the applicable strategy. Repeated inoculation resulted in a better COD and Cu removal performance (76.2 ± 2.6% and 98.5 ± 0.3%, respectively) than those of one-time inoculation (69.0 ± 2.0% and 98.0 ± 0.3%, respectively). The most functionally stable, balanced and resistant bacterial community was formed in the one-time inoculation system while for fungal community it was formed in the repeated inoculation system.

Inhibitory Effect of Phenol on Phosphorus Removal Performance of an EBPR System

An SBR reactor was operated to study the inhibitory effect of different concentrations of phenol (5, 10, 30, 50, 100, 150, and 200 mg·L-1) on the phosphorus removal performance of an EBPR system. The results showed that when the phenol concentration was no higher than 50 mg·L-1, the removal efficiencies of COD and PO43--P were above 85%. The system showed efficient pollutant removal performance. However, when phenol was higher than 100 mg·L-1, phosphorus removal performance of the reactor decreased drastically. When phenol concentration was 200 mg·L-1, the system lost phosphorus removal performance after only 22 cycles. The average COD removal efficiency dropped to 61.3%, and high removal performance recovery was not observed in the short term. Meanwhile, it was found that long-term dosing of phenol inhibited phosphorus removal of the sludge subjected to EBPR. Furthermore, the inhibition on aerobic phosphate uptake was greater than that on anaerobic phosphate release. In addition, the limited sludge bulking disappeared gradually owing to acclimation of the sludge to toxicity with a low phenol concentration (≤ 50 mg·L-1). However, high concentration of phenol induced sludge bulking was difficult to recover. The short-term impact experiments showed that effluent COD and phosphorus fluctuation caused by phenol could be recovered gradually by removing phenol, suggesting that the inhibitory effect of phenol on phosphorus removal was reversible.

Technical note: Nutrient removal and microbial settlement in a full-scale subsurface wastewater infiltration system: Impact of varying hydraulic and organic loads and temperature

A series of experiments was conducted through a full-scale subsurface wastewater infiltration system (SWIS) to investigate the impact of hydraulic loading rate (HLR), organic loading rate (OLR) and underground temperature on nutrient removal and microbial settlement. Taking the hydraulic and treatment performance into consideration, HLR of 0.10 m3/(m2·d) was recommended with average NH3-N, TN, COD and TP removal rates of 82.6%, 81.5%, 80.9% and 90.9%, respectively.Considering treatment performance, OLR of 10.4 g BOD/(m2·d) was recommended with average NH3-N, TN, COD and TP removal rates of 88.1%, 84.8%, 86.3% and 91.3%, respectively. The number of nitrifying bacteria in each layer in the matrix decreased with increasing HLR, and the number of denitrifying bacteria increased with increasing HLR, at 0.8 and 1.0 m depths. When OLR increased, the number of bacteria and denitrifying bacteria at 0.8 and 1.0 m depths increased, and the number of nitrifying bacteria decreased. Average NH3-N, TN and COD removal rates increased with underground temperature increasing. The number of bacteria, nitrifying bacteria at 0.4 and 0.6 m depths and denitrifying bacteria at 0.8 and 1.0 m depths, increased with underground temperature increasing.

Investigation of the treatability of molasses and industrial oily wastewater mixture by an anaerobic membrane hybrid system

In this study, the anaerobic treatability of automotive industry wastewater and its treatment in the subsequent membrane system were examined by using molasses, which is a waste of the sugar industry, as a co-substrate. Organic loadings of 3-3, 5-4, and 5gCOD/L/day were applied to a UASB reactor made of steel with a working volume of 7 L. The hydraulic retention time (HRT) was kept constant at 2 days. Temperature, pH, COD, alkalinity, Volatile Fatty acid (VFA) and biogas were monitored. The best COD removal was achieved at the value of 4 gCOD/L/day. The average COD removal rate was 77%. The effluent from the UASB reactor was transferred to the membrane system. The flux reductions of the PW10 kDa UF membrane at different concentrations were 1.717 gCOD/L, 1.934 gCOD/L, 2.257 gCOD/L, 4 gCOD/L, and 8 gCOD/L, and they were 90.78%, 42.69%, 45.88%, 51.00%, and 56.60%, respectively, at the input concentrations. The flux reductions of the UE50 100 kDa UF membrane at the input concentrations of 4 gCOD/L and 8 gCOD/L were 76.00% and 66.25%, respectively. It was determined that the UE50 100 kDa membrane caused more fouling compared to the PW 10 kDa UF membrane. Pore fouling models were determined for the flux reduction in the membranes and the mechanism behind it. Heavy metal and organic matter removals were examined in the effluent obtained from the membrane experiments.

A comparative study of macrophytes influence on performance of hybrid vermifilter for dairy wastewater treatment

Population increase and speedy urbanization are two major driving factors for scarcity of water in present time. To fulfil such water demand, reuse of industrial wastewater is necessary after essential purification. Vermifilter coupled with macrophyte filter is one of the promising technology for the treatment of organics and nutrient rich wastewater. In the present study, various macrophytes have been planted in vermifilter to study their effect on pollutants removal efficiency. Four sets of reactors R1, R2, R3 and R4 were designed and each set of reactor consisted of two units: vertical flow (VF) and horizontal flow (HF) unit. R1, R2 and R3 were planted with Canna indica, Saccharum spontaneum and Typha angustifolia, respectively, whereas R4 was without any macrophyte. Earthworm Eisenia fetida was inserted in all the four reactors. VF units of all hybrid vermifilter were loaded with synthetic dairy wastewater at hydraulic loading rate (HLR) of 0.6 m d−1. Effluents were collected at the bottom of the VF unit and channelled to the HF unit. Final effluent was collected at the end of the HF unit. The order of average percentage removal of COD was R1 (82.8%) > R3 (78.9%) > R2 (75.5%) > R4 (69.4%). Organics and nutrients were targeted to remove in the filter as these pollutants make major fraction in real dairy wastewater compare to antibiotics and other emerging contaminants. Presence of very few kind and low amount of antibiotics in dairy wastewater like lincomycin, chlortetracycline, etc. have been reported in literature.

DENITRIFICATION OF WASTEWATER TREATMENT PLANT EFFLUENT USING ANAEROBIC BACTERIAL BED REACTOR IMMERSED : OPERATING PERFORMANCE

In this study, a heterotrophic denitrification was designed for domestic wastewater treatment with unexpected water flows at different loading rates. Benefited from excellent removal ability COD, shorten operating time and lower maintenance cost. During the time of operation (six months), injection of nitrate was made in the influent RALBI 1 while the RALBI 2 was fed with sewage without addition of nitrate. The COD concentration in the influent of the two reactors was the same. This two reactors (RALBI1 and RALBI2) were fed with real wastewater for 172 days at 6 h HRT, the average COD removal were 71.55% and 54.82% for RALBI1 and RALBI2 respectively. The results showed that RALBI1 has good removal performance for COD compared with RALBI2. This could be due the injected nitrate in RALBI1 whose effect has further stimulated the activity of denitrifying bacteria.

DENITRIFICATION OF WASTEWATER TREATMENT PLANT EFFLUENT USING ANAEROBIC BACTERIAL BED REACTOR IMMERSED : OPERATING PERFORMANCE

In this study, a heterotrophic denitrification was designed for domestic wastewater treatment with unexpected water flows at different loading rates. Benefited from excellent removal ability COD, shorten operating time and lower maintenance cost. During the time of operation (six months), injection of nitrate was made in the influent RALBI 1 while the RALBI 2 was fed with sewage without addition of nitrate. The COD concentration in the influent of the two reactors was the same. This two reactors (RALBI1 and RALBI2) were fed with real wastewater for 172 days at 6 h HRT, the average COD removal were 71.55% and 54.82% for RALBI1 and RALBI2 respectively. The results showed that RALBI1 has good removal performance for COD compared with RALBI2. This could be due the injected nitrate in RALBI1 whose effect has further stimulated the activity of denitrifying bacteria.