Influent COD Concentration Research Articles

Effect of Municipal Wastewater Treatment by Biological - Ecological Filter (BEF)

A Pilot-scale study was conducted to treat municipal wastewater by Biological-Ecological filter (BEF), which is composed by anaerobic hydrolysis pool (AHP), high load biological filter (BF) and vermifilter (VF). The results demonstrated that when the influent concentrations of COD and NH3-N were in the range of 190~300 mg/L and 25~35 mg/L, respectively, the effluent concentration of them ranged from 45 to 65 mg/L and 8 to 20 mg/L with the average removal efficiency of 73.6% and 50%, respectively. Meanwhile, the effluent average SS concentration was less than 15 mg/L. The effluent quality could steadily meet the second level criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002) in China. The removal performance of fine zeolite was significantly better than the coarse one and heightening packing layer had little effect on the removal of COD and NH3-N. This study verified that BEF system for municipal wastewater treatment was feasible.

The Study on the Correlation between Removal Rate of Pollutants and its Influencing Factors in Xinxue River Constructed Wetland of China

Based on the monitoring data of February~December 2009 from Xinxue River Constructed Wetland, the regression analysis theory was used to establish mathematical models to determine the correlationship among the removal rate of pollutants, pollutant concentration, water temperature and influent water inflow, and optimize the operation parameters of the wetland. The multivariate linear regression equation was established with Statistical analysis software (SPSS). According to the correlation coefficient of the equation: the NH3-N removal has a significant positive correlation with water temperature, and a significant negative correlation with influent flow, total nitrogen removal has a significant positive correlation with water temperature, COD removal has a significant positive correlation with COD influent concentration. In addition, veracity of the model was also checked by contrasting the measured and analog data of March~June 2010 from the wetland. The results show that this model has a desired effect to estimate the removal rate and effluent concentration of COD and NH3-N, but undesirable to total nitrogen.

Reclamation of car washing wastewater by a hybrid system combining bio-carriers and non-woven membranes filtration

Due to the considerable temporal and spatial variations in precipitation in Taiwan, water usage authorities often impose restrictions on car washing, plant watering, and swimming pool refilling in drought season. In response to these water restrictions, the commercial carwash industry has taken measures to install reclamation systems for recycling and reusing carwash wastewater. Dissolved air flotation (DAF), sand filtration (SF), or Multi-media filtration (MMF) units are common reclamation systems for removing suspended solids (SS) in car wash wastewater. However, these technologies are usually ineffective at removing organic contaminants and result in the accumulation of organic contaminants in reclaimed water system. Alternative technologies with higher efficiency to produce high quality reclaimed water must be developed to meet the water demands of car wash industry during drought season. This paper presents a hybrid system that combines bio-carriers and non-woven membranes filtration. When installed in a car washing reclamation facility, this system can remove both SS and organic pollutants. A large amount of microorganisms can grow on the surfaces of porous bio-carriers made of polyurethane resin. Higher organic removal can be achieved using a bio-carrier system for low organic loading wastewater, such as car washing wastewater. A non-woven membrane made of non-woven material serves as microfiltration system to separate suspended solids from wastewater at a lower operating pressure than other types of ultrafiltration membranes. During 6 months of operation in a car wash facility in northern Taiwan, the average influent COD and SS concentrations were 67 mg/l and 230 mg/l, respectively. After treatment with bio-carriers and non-woven membrane filtration, the COD and SS concentrations in reclaimed water were less than 20 mg/l and 10 mg/l, respectively. During this test period, fresh water was only added to make up the water loss from vaporization to atmosphere and sludge disposal. Compared to DAF and SF in typical car washing reclamation systems, the proposed hybrid system achieved better performance in producing high quality reclaimed water and maintaining stable operation.

Simultaneous sludge reduction and nutrient removal (SSRNR) with interaction between Tubificidae and microorganisms: A full-scale study

A symbiotic ecosystem between Tubificidae and microorganisms was established at a full-scale wastewater treatment plant (WWTP). In this ecosystem Tubificidae were inoculated, and then adhered to the outer layers of carrier materials in an oxidation tank. During the long-term treatment of sewage volumes of 20,000 m 3 d −1, the excess sludge production rate was reduced from 0.21 to 0.051 kg m −3 and sludge settleability was significantly improved. When the influent concentrations of COD, NH 4 +–N, PO 4 −–P, and SS were in the ranges of 130.0–459.0 mg L −1, 14.2–27.5 mg L −1, 1.6–7.0 mg L −1, and 60.0–466.0 mg L −1, respectively, the COD and SS removal efficiency was increased by 8.7% and 13.6% within the symbiotic system compared to the control without Tubificidae. In addition, NH 4 +–N and phosphorus removal efficiency can also be improved. The results showed that both sludge reduction and nutrient removal were enhanced simultaneously significantly within the system utilizing the symbiotic interactions of Tubificidae and microorganisms.

Comparison of two mathematical models for correlating the organic matter removal efficiency with hydraulic retention time in a hybrid anaerobic baffled reactor treating molasses

A modelling of the anaerobic digestion process of molasses was conducted in a 70-L multistage anaerobic biofilm reactor or hybrid anaerobic baffled reactor with six compartments at an operating temperature of 26°C. Five hydraulic retention times (6, 16, 24, 72 and 120h) were studied at a constant influent COD concentration of 10,000mg/L. Two different kinetic models (one was based on a dispersion model with first-order kinetics for substrate consumption and the other based on a modification of the Young equation) were evaluated and compared to predict the organic matter removal efficiency or fractional conversion. The first-order kinetic constant obtained with the dispersion model was 0.28h(-1), the Peclet dispersion number being 45, with a mean relative error of 2%. The model based on the Young equation predicted the behaviour of the reactor more accurately showing deviations lower than 10% between the theoretical and experimental values of the fractional conversion, the mean relative error being 0.9% in this case.

Quick start-up of EGSB reactor treating fresh leachate of municipal solid waste

An expanded granular sludge bed (EGSB) reactor inoculated with anaerobic granular sludge was started up with its COD removal performance, self-balancing of pH, biogas production rate and characteristics of the granular sludge during the start-up period being investigated. The results indicated that the EGSB reactor can be started up successfully in 27 d by increasing the organic loading rate rapidly. The removal efficiency of COD was maintained above 93% with influent COD concentration of 25 000 mg/L and OLR of 37.94 kgCOD/(m3·d). The EGSB reactor with good pH self-balancing could be fed with fresh leachate of low pH value (4–5). The biogas production rate was closely related with OLR and COD reduction. Every gram of COD fed (consumed) to the reactor produced 0.34 LSTP (0.36 LSTP) biogas with 0.21 LSTP (0.23 LSTP) methane. Thus, 65%–70% of the produced biogas was methane. Sixty one percentage of COD fed to the reactor was converted to methane, another 33% was converted to biomass by metabolism, and the other 6% was left in the liquid phase. The specific methanogenic activity (SMA) of the granular sludge had increased by 92% after 27 d dynamic incubation. The granular sludge in the reactor had good settlement performance with majority diameter of 1–2 mm.

Ethanol degradation and the benefits of incremental priming in pilot-scale constructed wetlands

There has been significant global growth in the use of constructed wetlands for wastewater treatment. The fundamental microbial processes involved in the biodegradation of organic wastewater pollutants determine the range of design and operational parameters relevant to individual constructed wetlands. In this study, the biodegradation and mineralization of ethanol by acclimated and non-acclimated microbial populations in pilot-scale constructed wetlands were compared. By increasing the pollutant concentration at incremental intervals (incremental priming), the biodegradative capacity of a sand-filled constructed wetland was significantly enhanced. At an influent COD concentration of 15,800 mg L −1, no volatile fatty acids were detected in the effluent of an incrementally primed system and the maximum effluent COD concentration was 180 mg L −1. In contrast, an identical, unprimed system, amended with a lower concentration of COD (7587 mg L −1), exhibited a maximum effluent COD concentration of 1400 mg L −1, with the anaerobic metabolites, butyrate and propionate accounting for up to 83% of the effluent COD. It was demonstrated that the use of incremental priming, together with a vertical subsurface flow mode of operation enhanced long-term function of constructed wetlands. Future research should focus on determining the concentration gradients and incremental intervals necessary for optimal microbial acclimation to a range of organic pollutants and/or wastewaters, in order to minimize start-up times without significantly impairing the benefits derived from incremental priming.

Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactor

Moving bed biofilm reactor (MBBR) was used to treat real coal gasification wastewater. Nitrification of the MBBR was inhibited almost completely during start-up period. Sudden increase of influent total NH 3 concentration was the main factor inducing nitrification inhibition. Increasing DO concentration in the bulk liquid (from 2 to 3 mg/L) had little effect on nitrification recovery. Nitrification of the MBBR recovered partially by the addition of nitrifying sludge into the reactor and almost ceased within 5 days. Nitrification ratio of the MBBR achieved 65% within 12 days by increasing dilute ratio of the influent wastewater with tap water. The ratio of nitrification decreased to 25% when influent COD concentration increased from 650 to 1000 mg/L after nitrification recovery and recovered 70% for another 4 days.

Study on Livestock and Poultry Farming Wastewater Treatment Using a Hybrid Baffled Reactor

In this paper aerobic process was applied in an anaerobic baffled reactor to form an innovative Hybrid Baffled Reactor (HBR), which was used to investigate the treatment effect of livestock and poultry farming wastewater. Biofilm cultivation, the influence of Hydraulic Retention Time (HRT) and treatment effect in three tanks were also discussed. The study result showed that good COD and NH4+-N removal efficiency was achieved in the reactor. When the influent COD concentration, NH4+-N concentration and HRT were 900 mg/L, 200 mg/L and 24 h, the concentrations of COD and NH4+-N in the outlet were smaller than 100 mg/L and 70 mg/L, and COD removal efficiency and nitrification rate were 90% and 70% respectively.

The Nitrogen Variation of Sauce Wastewater with Different Influent COD Concentration

With rapid development of sauce industry, the production of the sauce is increasing in recent years. The sauce wastewater is doing greater harm to the water environment in China. In order to tackle this problem, the influent COD concentration influence on nitrogen variation of sauce wastewater was investigated. The results showed that the influent COD has a different effect for ammonia nitrogen, nitrite and nitrate. When the influent COD concentration was 600mg/L, 500mg and 300mg/L respectively, the effluent ammonia nitrogen was at 4.3mg/L, 1.8mg/L and 1.0mg/L. And the ammonia nitrogen removal efficiency was more than 90%. Meanwhile the nitrate and nitrite accumulated steadily with the same variation tendency.

Control of Start-up and Operation in Continuous Fermentation of Bio-Hydrogen Production Reactor

Bio-hydrogen production from diluted molasses by anaerobic activated sludge was investigated in a continuous stirred-tank reactor (CSTR) under condition of continuous flow in this study. Research shows that the reactor started up under the condition of influent COD concentration 3000mg/L, HRT8h, pH6.5~7.5 and (35±1) °C. The process performed steadily and a dominant butyric acid and acetic acid type fermentation population was established, acetic acid and butyric acid accounted for about 80% in the liquid fermentation products. The effluent PH value was maintained about 5.0. The biogas yield could reach at 4.87L/d while hydrogen yield reached 41.25mL/d under the condition. When influent COD concentration rose to 5500 mg/L, the biogas yield and hydrogen yield as high as 9.45L/d and 119.98mL/d were obtained.

Acclimation of Anaerobic Granular Sludge and 2,6-DNP Removal in the Upflow Anaerobic Sludge Blanket (UASB) Reactors

Characteristics of anaerobic granules before and after acclimation were studied using glucose as co-substrate. Removal efficiencies of 2,6-dinitrophenol (2,6-DNP) using two different co-substrates were investigated in two lab-scale UASB reactors. Granular sludge acclimatized to the wastewater containing 2,6-DNP through 3 months. After acclimation, SEM pictures of the granular biomass showed that Filamentous bacteria were the predominant bacteria on the surface of granules. Throughout the study of 2,6-DNP anaerobic degradation with different co-substrates, influent COD concentration was kept constant as about 2500 mg l-1. Maximum 2,6-DNP concentration was 170.0 mg l-1 and 2,6-DNP removal efficiencies were always more than 98.0% using glucose as co-substrate, keeping hydraulic retention time (HRT) as 35 h. When using sodium acetate as co-substrate and keeping HRT as 30 h, maximum 2,6-DNP concentration was up to 189.5 mg l-1 and over 99.2% 2,6-DNP removal efficiencies could be obtained.

Monitoring of microbial storage products and the effciency of an activated sludge plant performing anoxic phosphorus removal under different operational conditions

The present work focuses on the operation of a continuous flow laboratory scale plant for enhanced biological phosphorus removal (EBPR) from synthetic wastewater. After the acclimatization period, basic operational conditions, namely the influent COD concentration and the anoxic to anaerobic tank volumes ratio, varied, in order to evaluate their impact to the system performance. The progressive increase of the influent COD concentration from 200 mg COD/l to 300 and 400 with constant influent phosphate concentration of 15 mg PO -3 4 -P/l, led to proportional increase of the intracellular PHAs used during the anoxic phosphorus uptake process and to the respective amount of nitrate denitrified. However, the highest phosphorus uptake rate and the maximum net phosphorus removal were observed for the influent COD/P concentrations ratio of 20 (300 mg COD/l). Interestingly, this was also the ratio where the maximum carbohydrates synthesis and biomass P content during the anoxic phase were observed, indicating this, as the optimum ratio for the system efficiency. In a second operational period and for this particular COD/P ratio, three different anaerobic hydraulic residence times (HRT) were imposed, by increasing the volume of the anaerobic tank, in order to achieve anoxic to anaerobic HRT ratios of 2.33, 1.75 and 1.4. The experimental results indicated that decreased ratio values led to increased PHAs utilization for phosphorus removal. Furthermore, despite the considerable increase of the specific P uptake rate, the specific anaerobic P release rate remained almost constant, irrespective to the anoxic to anaerobic HRT ratio. The maximum net phosphorus removal was observed for the minimum ratio, indicating that increased anaerobic contact time enhances the activity of polyphosphate accumulating organisms (PAOs) in the EBPR plant. The biomass growth yield was not influenced by the anoxic to anaerobic HRT ratio and remained constant at 0.27 gVSS/gCOD. Phosphorus removal under alternative anaerobic/anoxic conditions proved its practical feasibility and satisfactory efficiency in a continuous flow activated sludge system.

Treatment of coal gasification wastewater by a two-continuous UASB system with step-feed for COD and phenols removal

A two-continuous mesophilic (37 ± 2 °C) UASB system with step-feed was investigated as an attractive optimization strategy for enhancing COD and total phenols removal of the system and improving aerobic biodegradability of real coal gasification wastewater. Through the step-feed period, the maximum removal efficiencies of COD and total phenols reached 55–60% and 58–63% respectively in the system, at an influent flow distribution ratio of 0.2 and influent COD concentration of 2500 mg/L; the corresponding efficiencies were at low levels of 45–50% and 43–50% respectively at total HRT of 48 h during the single-feed period. The maximum specific methanogenic activity and substrate utilization rate were 592 ± 16 mg COD-CH 4/(gVSS d) and 89 ± 12 mg phenol/(gVSS d) during the step-feed operation. After the anaerobic digestion with step-feed, the aerobic effluent COD concentration decreased from 270 ± 9 to 215 ± 10 mg/L. The results suggested that step-feed enhanced the degradation of refractory organics in the second reactor.

Effect of Organic Loading Rate on Bio-Hydrogen Production in Continuous Stirred Tank Reactor

Hydrogen is a kind of ideal clean energy sources. With low energy consumption, environmental protection and other advantages, biological hydrogen production technology become the hotspot of current study home and abroad. The distribution energy technology for producing hydrogen can get hydrogen when deal with waste water. For finding out the industralized feasibility of continuous H2 bio-production,the ability of H2-production via facultative anaerobe,optimum hydraulic retention time(HRT) and optimum organic loading rate(OLR) were aslo studied. With a temperature of (35±1)°C，HRT of 8 h，the CSTR inoculated with activated sludge ,and the progression is increasing organic loading rate gradually. Six OLRs were examined, ranging from 2 to 12 g COD/L.d, with the mass of molasses ranging from 1.3 to 10 g COD/L. While COD was up to 4g/L(OLR 12kg/(m3•d)), all molasses was utilized and the H2 yield was not significantly influenced by OLR. At the intermediate COD of 6g/l (OLR 18kg/(m3•d)), the H2 yield was maximized at about 30 L/d H2 (mol molasses. Conv.), which was 17.9% and 55.9% higher than those of OLR 6 kg/(m3.d) and OLR 12 kg/(m3.d),respectively. When the influent COD concentration raised to 12g/L(OLR 30kg/(m3•d)), the reactor were overloaded, the hydrogen yield decreased drastically，hydrogen evolution rate decreased to zero. Exceeding OLR would arouse great change of internal environment parameters, such as pH, ALK(aikalinity), ORP(oxidation-reduction potential) in CSTR, and the microbial community structure would change while the metabolism of microorganism was inhibited badly.

Kinetic development and evaluation of membrane sequencing batch reactor (MSBR) with mixed cultures photosynthetic bacteria for dairy wastewater treatment

This experimental study was conducted to evaluate a membrane sequencing batch reactor (MSBR) with mixed culture photosynthetic bacteria for dairy wastewater treatment. The study was undertaken in two steps: laboratory and pilot scale experiments. In the first step, kinetics analysis of the MSBR was carried out in a laboratory scale experiment with influent COD concentration of 2500 mg/L. The pilot scale experiment was conducted to investigate the performance of the MSBR and checked the suitability of the kinetics for an engineering design. The kinetic coefficients K s, k, k d, Y and μ m were found to be 174-mg-COD/L, 7.42/d, 0.1383/d, 0.2281/d and 1.69/d, respectively. There were some deviations of COD removal efficiency between the design value and the actual value. From the kinetics estimation, COD effluent from the design was 27 mg/L while the average actual COD effluent from the experiment was 149 mg/L. Due to the different light source condition, the factors relating to light energy (i.e. L f and IR %) must be incorporated into engineering design and performance prediction with these kinetic coefficients of the photosynthetic MSBR.

Performance of two combined anaerobic–aerobic biofilters packed with clay or plastic media for the treatment of highly concentrated effluent

Biological treatment of high-strength carbon and nitrogen synthetic wastewater by two combined anaerobic–aerobic biofiltration systems packed with clay (system 1) or plastic media (system 2) has been studied for 143 days. Four phases of operating conditions were carried out with an influent COD and TKN concentrations varied from 2595 to 5969 mg/L and 510 to 1866 mg/L, respectively. Both systems exhibited excellent COD removal performance and the average removal efficiencies were superior to 90% for a loading of 2 to 4 kg COD/m 3/d. The BOD 5 average removal during the four operating phases varied from 91 to 98%. Total nitrogen removal occurred in the aerobic stage showing 60% and 77% of elimination obtained for aerobic filters of systems 1 and 2, respectively. Nitrogen removal was related to many factors such as nitrification/denitrification, bacterial assimilation and NH 3-stripping. The aerobic filter packed with plastic media produced less nitrates than the other filter. This may due to an enhancement of the denitrification or to the inhibition of nitrobacter by free NH 3. Effluent nitrite concentrations confirmed the possibility of NH 3-inhibition. Phosphorus removal was also at acceptable level for both systems with yields varied from 50% (system 1) to 70% (system 2).

Kinetics of COD Removal in a Biological Aerated Filter in the Presence of 2,4,6-Trinitrophenol (Picric Acid)

An empirical model for COD removal in a biological aerated filter (BAF) in the presence of 2,4,6-trinitrophenol (TNP) was developed, which related effluent COD to influent COD or hydraulic loading rate along the bed height. The overall reaction rate for substrate biodegradation could be described as pseudo first order. The experimental data of COD removal against reactor height were used to calculate the parameters in the empirical model. The COD concentration at different reactor height was expressed as a function of influent COD concentration and hydraulic loading rate, ln( C 0/C) = 0.124 H/Q 0.77 0 and ln(C/ 0) = −5.63 H/ L 0.94}, respectively, under the experimental condition. The models may be used to predict the COD removal profiles along the reactor height at different hydraulic loading rates and influent COD concentration for design, selection and sizing of BAF.

Effect of adding nitrate on the performance of a multistage biofilter used for anaerobic treatment of high-strength wastewater

This laboratory research was carried out to evaluate the performance of a multistage anaerobic biofilm reactor, with six compartments and a working volume of 70 L, for the treatment of a strong synthetic nitrogenous and high-strength wastewater at an operational temperature of 26 ± 0.5 °C. Initially, the performance of the reactor was studied when subjected to an increase in the hydraulic retention time (HRT) at a constant influent COD concentration of 10,000 mg/L. Five different HRTs were studied: 0.25, 0.67, 1, 3 and 5 days, which were equivalent to 6, 16, 24, 72 and 120 h, respectively. By increasing the HRTs from 6 h to 1 day, COD and BOD removal efficiencies were increased from 63% to 84% and from 66% to 87%, respectively. Moreover, at an HRT of 3 days, COD and BOD removal efficiencies were equal, reaching 93%. In the second phase of the research, the effect of adding nitrate with a concentration of 3000 mg/L at an influent organic loading rate of 10 g COD/L d was researched on the reactor performance and the amount of biogas produced. Denitrification took place almost solely in the first three compartments of the reactor, with efficiencies of 85%, 95% and 98%, respectively. The nitrite produced was only detected in the first and second compartments at concentrations of 138 and 24 mg/L, respectively. In addition, no accumulation of nitrite was detected in the reactor. Furthermore, the denitrification caused an increase in the total volume of produced biogas from 102 to 178 L/d.

Kinetic model for an up-flow anaerobic packed bed bioreactor: Dairy wastewater treatment

Kinetic studies of anaerobic digestion process of cheese whey were conducted in a pilot-scale up-flow anaerobic packed bed bioreactor (UAPB). An influent COD concentration of 59419 mg/l was utilized at steady state condition. Logistic and Monod kinetic models were employed to describe microbial activities of cheese whey in an anaerobic digester. The hydraulic retention times (HRT) in the range of 6 to 24 h were investigated throughout the experiments. Lactose conversions were 58.5 and 99.4% for HRT of 6 and 16 h, respectively. The methane production rates were 6.57 and 3.25 l/h for HRT of 6 and 24 h, respectively. Monod biokinetic coefficients, K s, s, s, m m and methane yield (Y M ) were 8.59, 7.63 (h -1 ) and 0.11 (g methane/g lactose), respectively