Effluent COD Concentration Research Articles

Denitrification process of deep bed denitrification filter for secondary effluent from urban sewage treatment plant

In recent years, the sewage discharge standards are getting stricter, and advanced wastewater treatment is more important. Therefore, further advanced treatment of the effluent from the wastewater treatment plant has become a research hotspot. In this study, deep bed denitrification filter (DBDF) was used to treat secondary effluent from urban sewage treatment plants. The effects of different carbon and nitrogen ratios (C/N) and hydraulic retention time (HRT) on the nitrogen removal efficiency of the system were investigated. The results showed that the optimum C/N of the reactor was 5, and the optimum HRT was 0.5h. After running for 15 days under the optimal conditions, the results showed that DBDF ran stably, and the denitrification effect was good. The average effluent concentrations of COD and TN were 16.4 and 6.9mg/L, and the average removal rates were 77.0% and 57.7% respectively.

Hydrodynamics and mathematical modelling in a low HRT inverse fluidized-bed reactor for biological sulphate reduction.

Biological reduction of sulphate at low hydraulic retention time (HRT) is presented in this paper. A sulphidogenic inverse fluidized-bed bioreactor (IFBB) was operated successfully at a progressively decreasing HRT from 1 to 0.125days for a total of 155days. Synthetic wastewater containing sulphate at a concentration of 745 (± 17)mg/L was used. COD was supplied as lactate in variable concentrations at COD/SO42- ratios of 1.2-2.4. The pH of the feed ranged between 5.2 and 6.2. The highest measured removal rates were 2646 and 4866mg SO42-/Lday at an HRT of 0.25 and 0.125days, respectively, using a COD/SO42- ratio of 2.3. The biological sulphate reduction was limited by the influent COD concentrations at a COD/SO42- ratio < 2.3. The IFBB ensured biomass retention at a maximum liquid residence time of θ = 3.84 (± 0.013), according to the residence time distribution analysis. Hydrodynamic studies were carried out at recirculation rates of 0, 200, 300, 350, 400, and 500L/h to measure the relative bed expansion, the mixing pattern, and the fluidization characteristics of the reactor. A dynamic model is also developed based on COD and sulphate as the two limiting substrates in a Monod-type kinetic equation describing the kinetics of lactate oxidation by SRB. A set of the following parameters [Formula: see text] = 0.23mg COD of VSS/mg lactate, µmax = 1.758day- 1, KCOD = 956mg COD of lactate/L, [Formula: see text] = 316mg SO42-/L, kd = 0.024day- 1, tres = 5.7days, and kexchange = 0.4day- 1 simulated adequately the residual effluent COD and sulphate concentrations, the produced sulphide concentration as well as the pH of the IFBB effluent. Low HRT values, shown efficient in this study, are prerequisite for industrial applicability and economic feasibility of the sulphur reduction process. In addition, the developed model can be used for optimum experimental design and further process upscale and development.

Adding maize cobs to vertical subsurface flow constructed wetlands treating marine recirculating aquaculture system effluents: Carbon releasing kinetics and intensified nitrogen removal

This study aims to investigate the releasing behaviors of maize cobs with or without alkali (i.e. NaOH) pretreatment in seawater and distilled water, and to evaluate the effects of maize cobs addition (solid biomass and lixivium) on nitrogen removal in saline constructed wetland (CW) treating marine recirculating aquaculture system (RAS) effluents. Results revealed NaOH-treated maize cobs released carbon more efficiently, whether in seawater or in distilled water. Compared to distilled water, seawater conditions promoted carbon releasing. CW with maize cobs biomass and lixivium addition had high NO3-N removal efficiencies without significant difference, i.e. 94.9 ± 6.0% and 87.1 ± 13.2%, respectively. While CW with maize cobs biomass addition had higher effluent COD concentrations (16.3 ± 3.6 mg L−1) compared with those adding lixivium (2.1 ± 0.4 mg L−1). The study suggested adding maize cobs lixivium to be feasible and effective way to enhance nitrogen removal in saline CW.

Day/night temperature differences (DNTD) trigger changes in nutrient removal and functional bacteria in membrane bioreactors

Temperature is a well-known environmental stress that influences both microbial metabolism and community structure in the biological wastewater treatment systems. In this study, responses of biological performance and sludge microbiota to the long-term day/night temperature differences (DNTD) were investigated in membrane bioreactors (MBRs). The results showed that the functional bacteria could sustained their ecological functions at low DNTD (20/30 °C), resulting in relatively stable performance with respect to nutrient removal. However, when the activated sludge was subjected to a high DNTD (17/33 °C), the effluent concentrations of COD, TN and TP were significantly higher in MBR-B than that in MBR-A. In addition, more severe membrane fouling occurred under the perturbation of high DNTD as revealed by the transmembrane pressure (TMP) profile, which was mainly attributed to the accumulation of extracellular polymeric substances (EPS). The results of 16S rRNA gene sequencing showed that DNTD showed negligible effect on the bacterial community structures. Nonetheless, the functional bacteria responded differently to DNTD, which were in accordance with the bioreactor performances. Specifically, Nitrospina (NOB) and Tetrasphaera (PAOs) appeared to be sensitive to both low and high DNTD. In contrast, a low DNTD showed marginal effects on the denitrifiers, while a high DNTD significantly decreased their abundances. More strikingly, filamentous bulking bacteria were found to be well-adapted to DNTD, indicating their tolerance to the daily temperature fluctuation. This study will advance our knowledge regarding the response of microbial ecology of activated sludge to daily temperature variations in full-scale MBRs.

Pilot study of cold-rolling wastewater treatment using single-stage anaerobic fluidized membrane bioreactor

A pilot-scale single-stage anaerobic fluidized membrane bioreactor (AFMBR) was firstly used in this study to treat cold-rolling emulsion wastewater from steel industry. It was continuously operated for 302 days with influent COD concentration of 860–1120 mg/L. Under a hydraulic retention time of 1.5 d, the average effluent COD concentration of 72 mg/L achieved corresponding 90% of COD removal. The permeate flux was varied between 1.7 and 2.9 L/m2/h during operation which decreased with increased biomass concentration inside AFMBR. The trans-membrane pressure (TMP) was generally around 35–40 kPa, however, it increased up to 60 kPa when volatile suspended solid increased to above 2.5 g/L. Both flux and TMP data reveal the importance of biomass control for AFMBR operation. Results from terminal restriction fragment length polymorphism (T-RFLP) show the genus Methanosaeta was dominant on GAC and it shared dominance with the genera Methanomethylovorans and Methanosarcina in suspended sludge.

Biological denitrification from mature landfill leachate using a food-waste-derived carbon source

The mature landfill leachate containing high ammonia concentration (>1000 mg/L) is a serious threat to environment; however, the low COD to TN ratio (C/N, <3) strongly inhibits the denitrification process and poses a severe obstacle for efficient treatment. Herein, two kinds of acidogenic liquids, fermented from oil-removed food waste and oil-added food waste, were first applied as external carbon sources for the biological nitrogen removal from mature landfill leachate in an aerobic/anoxic membrane bioreactor. “Acidogenic liquid b” served quite better than commercial sodium acetate, considering the higher denitrification efficiency and the slightly rapider denitrification rate. The effect of C/N and temperature were investigated under hydraulic retention time (HRT) of 7 d, which showed that C/N ≥ 7 (25 °C) was enough to meet the general discharge standards of NH4+-N, TN and COD in China. Even for some special areas of China, the more stringent discharge standards (NH4+-N ≤ 8 mg/L, TN ≤ 20 mg/L) could also be achieved under longer HRT of 14 d and C/N ≥ 6. Notably, the COD concentration in effluent could also be well reduced to 50–55 mg/L, without further physical-chemical treatment. This proposed strategy, involving the high-value utilization of food waste, is thus promising for efficient nitrogen removal from mature landfill leachate.

Advanced treatment of bio-treated coal chemical wastewater by a novel combination of microbubble catalytic ozonation and biological process

Abstract The advanced treatment performance of real bio-treated coal chemical wastewater (BCCW) by a novel combination of microbubble catalytic ozonation and biological process was investigated. The refractory compounds in BCCW could be degraded effectively by microbubble catalytic ozonation treatment, which resulted in efficient COD removal, inorganic nitrogen release and significant improvement of biodegradability. The dissolved oxygen (DO) supplied by microbubble catalytic ozonation was also enough for aerobic digestion in the following biological treatment even without aeration. The biodegradable COD and ammonia nitrogen released in microbubble catalytic ozonation treatment could be removed further in the following biological treatment efficiently. There was no off-gas ozone required to be treated due to high ozone utilization efficiency of close to 100%. The ratio of ozone dosage to influent COD amount showed a marked impact on the performance of the combination treatment system and its optimal value obtained in this study was 0.44 mg/mg. In this case, for microbubble catalytic ozonation, the COD removal efficiency was 32.16%, the ratio of ozone dosage to COD removed was 1.38 mg/mg and the ozone utilization efficiency was 98.0%. For biological treatment, the COD removal efficiency was 41.93%. For the combination system, the total COD removal efficiency was 60.82%, the average final effluent COD concentration was 91.5 mg/L and the estimated total ratio of ozone dosage to COD removed was 0.68 mg/mg. Therefore, the combination of microbubble catalytic ozonation and biological process is an effective and economical solution for advanced treatment of BCCW.

Effect of organic nitrogen concentration on the efficiency of trickling filters

The study was conducted in Poland at six selected wastewater treatment plants (WWTP) based on the trickling filters Bioclere® technology. The aim of the study was to find the relationship between the influent organic nitrogen concentration and the purification efficiency expressed as effluent COD concentration. In the tests performed, the COD to BOD5 relationship was close to 2 and the ratio of BOD5 to TN was lower than 4. The research indicated that this specific chemical composition of raw wastewater causes appearance of filamentous bacteria on the surface of trickling filter filling and strongly affect the effluent quality.

Nutrient leaching from extensive green roofs with different substrate compositions: a laboratory study.

To investigate nutrient leaching from extensive green roofs, green roof platforms were established to investigate the effluent quantity and quality during artificial rainfall. When the influent volume reached three times the empty bed volume, for which the cumulative rainfall was around 300 mm, the effluent TP and COD concentrations of green roof platforms filled with peat soil did not tend to stabilize. For a long-term operation, the substrate depths had little significant influence on TN, TP and COD concentrations of the green roof effluents. A normalized cumulative emission process method was proposed to discuss the difference in various pollutant leaching processes. Obvious differences in the leaching process of different contaminants for green roof platforms filled with various substrates were observed. For the green roof filled with modified substrates, the nitrogen and phosphorus pollutant leaching rates were relatively high in the initial stage of green roof operation and the phosphorus leaching rate was higher than that of nitrogen. The green roof is a sink for TN, but not for TP and COD in this study. The outcomes are critical for the selection of green roof substrates and also contribute to green roof maintenance.

A novel bio-electro-Fenton process with FeVO4/CF cathode on advanced treatment of coal gasification wastewater

Abstract An investigation was carried out aimed at checking the feasibility of the novel bio-electro-Fenton process with FeVO4/CF cathode on advanced treatment of coal gasification wastewater. The maximum power density arrived 849.7 mW/m3 in MFC-FeVO4/CF system, which was corresponding to a current density of 2.6 A/m3 at the voltage of 326.8 mV. The concentration of BOD5, COD, TOC and total phenols in the cathode effluent under short-circuit conditions were 4.5 mg/L, 32.5 mg/L, 8.8 mg/L and 15.6 mg/L, respectively, which all met the class-I criteria of the Integrated Wastewater Discharge Standard. FeVO4/CF could be employed as a two-way Fenton-like catalyst that leads to the production of more reactive oxygen species. The in situ generation of Fenton-like reagents (Fe(II, V(IV) and H2O2) at the cathode was demonstrated by the cyclic voltammetry measurement. This novel process provides a cost-effective alternative to extend the practical merits of traditional MFCs and Fenton towards advanced treatment of industrial wastewater.

Use of dewatered sludge as microbial inoculum of a subsurface wastewater infiltration system: effect on start-up and pollutant removal

Brown earth–based subsurface wastewater infiltration systems (SWISs) inoculated with/without dewatered sludge were constructed and operated under the same conditions to boost the application of SWIS in brown soil areas. Start-up period of SWIS with dewatered sludge was 28 days, 12 days shorter than that of SWIS without dewatered sludge. COD, NH 3 -N and TN removal efficiencies of dewatered sludge as microbial inoculum for SWIS were higher than that of SWIS without dewatered sludge under hydraulic loading rates (HLR) of 0.04, 0.07, 0.1 and 0.13 m 3 ·m −2 ·d −1 . Effluent concentrations of COD, NH 3 -N and TN in the SWIS inoculated with dewatered sludge were 44.51±4.13, 7.35 ± 0.24 and 14.03 ± 0.31 mg·L −1 under HLR of 0.13 m 3 ·m −2 ·d −1 , which were simultaneously lower than Chinese criteria for water discharge from municipal wastewater treatment plants. The number of bacteria, nitrifying bacteria and denitrifying bacteria in dewatered sludge as microbial inoculum for SWIS were higher than that in SWIS without dewatered sludge under the same HLR. The results will be helpful in promoting the application of dewatered sludge as microbial inoculum in brown earth–based SWISs for the purpose of shortening start-up period, effecting high levels of pollutant removal and recycling waste. Keywords : subsurface wastewater infiltration system, dewatered sludge, start-up, inoculum

Effect of Hydraulic Retention Time on the Performance of High-Rate Activated Sludge System: a Pilot-Scale Study

Conventional activated sludge (CAS) technology has been the most commonly applied technology for treatment of municipal wastewater for more than a century; however, a significant portion of energy content of the wastewater cannot be recovered by this technology. Therefore, different modifications can be applied to the CAS technology in order to increase the energy harvesting from wastewaters. In this paper, physically treated wastewater from a municipal preliminary wastewater treatment plant (WWTP) was treated at a pilot-scale high-rate activated sludge (HRAS) system. The HRAS system was operated under three different hydraulic retention times (HRTs) and the treatment performances were evaluated. Within this concept, HRTs of 130, 95, and 60 min were tested. The results revealed that total chemical oxygen demand (tCOD) removal of 59% was achievable and the effluent total suspended solids (TSS) concentration was 90 mg/L at the HRT of 60 min. Effluent COD and TSS concentrations decreased with the decrease in HRT by means of enhanced flocculation and sedimentation. This is confirmed by the improvement of sludge volume index (SVI) values at decreased HRTs. The calculated mass balance showed that more COD was diverted to sludge stream with decrease in HRT. Diversion of more COD to sludge can improve the energy balance of wastewater treatment by the application of anaerobic sludge digestion. By this way, HRAS process would be a promising technology in the concept of energy efficient wastewater treatment systems.

Rapid nitrification process upgrade coupled with succession of the microbial community in a full-scale municipal wastewater treatment plant (WWTP)

Bioaugmentation was used to upgrade the nitrification process in a full-scale municipal WWTP with an A2/O system. A mixture of nitrifying bacteria was inoculated into the bioreactor for a final concentration of 1% (v/v). The upgrade process took 25 days, and the NH4+-N removals reached 94.6% (increased at least by 75%). The effluent concentrations of COD and NH4+-N stabilized at <30 mg/L and <4 mg/L even when the corresponding influent concentrations were over 300 mg/L and 60 mg/L, which met the first-class requirement of the National Municipal Wastewater Discharge Standards of China (COD ≤ 50 mg/L, NH4+-N ≤ 5 mg/L). The succession of the microbial community showed the enhanced NH4+-N removal efficiency mainly resulted from the persistence of introduced ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which increased from 0% to 0.4% and from 0.01% to 2.1%, respectively. This bioaugmentation was shown as an effective technology for upgrading or retrofitting conventional systems to tertiary-level.

Performance of a Field Scale Combined Biofilters System for the Purification of Micro-polluted Urban Shallow Lake

Combined biofilters system was developed to purify a micro-polluted urban shallow lake. The performance of the system was investigated from January 2007 to December 2011. The results showed that the effluent concentration of COD dropped below 20 mg /L, NH4-N dropped below 0.2 mg /L, TN decreased below 1.0 mg/L, and TP decreased below 0.2 mg/L, all of the water quality indexes reached the class III standard of “Surface Water Quality Standards” (GB 3838-2002) except TP. The combined system showed strong anti-shock load and provided an option for the treatment of micro-polluted urban lake.

Modeling and simulation of a biological process for treating different COD:N ratio wastewater using an extended ASM1 model

The aim of this study was to establish a mathematical model for simulating a biological nutrient removal (BNR) process for treating wastewater with different COD:N ratios. Through phylogenetic analysis, the microbial communities in a cyclic activated sludge system (CASS) reactor under different COD:N ratios were quantitatively characterised, while the necessity of incorporating the microbial interaction mechanism in the extended ASM1 (E-ASM1) was validated. Since the newly introduced parameters affected the original kinetics in the activated sludge model No. 1 (ASM1), the poorly defined parameters were altered based on the batch experimental data taken from a lab-scale CASS and the results of a root-mean-square sensitivity analysis. The simulation results indicated that effluent COD and biopolymer concentrations decreased with an increase in influent COD:N ratio, while the trend was opposite for nitrification. Compared to the ASM1-SMP-EPS model, the extended ASM1 (E-ASM1) proved to be a preferable reference for the simulations of the CASS performance in substrate degradation and biopolymers formation mechanism, strongly suggesting that the interactive relationship among different bacteria and the biopolymer dynamics should be simultaneously included in this model.

Utilizing ion-exchange resin to improve recovery from organic shock-loading in an AnMBR treating sewage sludge

The addition of ion-exchange resin in a two-phase continuous AnMBR system treating primary sludge at ambient temperature (20 °C) was investigated as a means to improve reactor recovery after organic shock-loading. Four commercially available anion-exchange resins were evaluated for their ability to sorb soluble organics, specifically volatile fatty acids (VFA), from AnMBR effluent. The strong-base resin, Purolite TANEX, was determined the best resin for deployment in the continuous AnMBR having achieved the greatest removal of soluble chemical oxygen demand (sCOD) (up to 36%) and acetic acid (up to 48%) in preliminary batch testing. Addition of 100 and 300 g/L TANEX in the AnMBR system improved effluent quality reducing effluent COD concentrations by 48 and 75%, respectively, under normal operating conditions. After shock-loading with 16,000 mg COD/L as acetic acid, reactor recovery in terms of methane production was 9–58% faster with the addition of TANEX than without, under controlled pH conditions (pH: 7.4). After shock-loading the system twice without the addition of TANEX it was found that recovery improved by 19% suggesting that acclimation of the microbial community also played a role in reactor recovery. Microbial community analysis using 16 S Illumina MiSeq sequencing confirmed changes in the microbial community did occur in response to shock-loading, with higher relative abundance of Methanoscarcina in the majority of post-shock-load microbial communities. The highest relative abundance of Methanoscarcina (51–58%) was seen during operating periods with the addition of TANEX resin, leading to the conclusion that addition of the TANEX resin benefited reactor recovery by serving as a temporary physio-chemical sink for the excess acetic acid, allowing the microbial community time to adjust to their new environmental conditions and become better able to process the higher levels of acetic acid associated with the organic shock.

Metal Concentrations and Responses of Chironomid Larvae Exposed to Thailand Pulp and Paper Mill Effluent.

Pulp and paper mills (PPM) may discharge insufficiently treated waste into rivers and give rise to serious effects with aquatic life. This study investigated the biological response of the chironomid (Chironomus javanus, Kieffer) when exposed to PPM effluent. Effluent concentrations of BOD, COD, TKN, TS, Cr, Cu, Pb and Zn were high. Cd and Cr concentrations in chironomid were the most accumulated. Whole effluent toxicity on the chironomid test organism was significant as expressed by the percent survival and decreased with increasing concentration. Highest dry weight, head capsule and length of the chironomid test organism corresponded to 100% effluent at a specific time. Effect of dilution was assessed by using glutathione S-transferase activity on chironomid and corresponded to 6.25% effluent during 48-96h which was significantly increased in the chironomid. The results showed that the chironomid was sensitive to PPM effluent and toxicity tests can be used for assessing the effect of effluent on aquatic species.

Performance and microbial community structure characterization of a CIC anaerobic reactor for the treatment of cassava wastewater

A laboratory-scale controlling internal circulation (CIC) anaerobic reactor was developed to treat cassava wastewater. The hydraulic retention time (HRT), internal circulation ratio, and temperature were selected as main operating variables that could be optimized to increase efficiency of the reactor. Responses of microbial communities to changes in these parameters were investigated using high throughput sequencing (HTS) approach. With increasing internal circulation ratio, the COD removal efficiencies and gas production rates also increased. On the other hand, decreasing temperature to 20°C resulted to increase in the effluent COD concentration to 1000mgL−1, with low gas production rate of 0.10m3CH4kg−1·COD−1. Upon starting the internal circle of the CIC reactor, species diversity was reduced while species abundance increased. Specifically, Methanosarcinales increased from 32.82% to 39.69%, and Methanobacteriales from 33.72% to 54.77%. However, when the CIC reactor temperature was further reduced to 25°C, the abundance of Methanobacteria decreased to 33.35%. Results showed the microbial community shift was observed at different internal circulation ratio and temperature, influencing the pollutants removal rate and gas production rate.

Mainstream upflow nitritation-anammox system with hybrid anaerobic pretreatment: Long-term performance and microbial community dynamics

Mainstream nitritation-anammox is of strong interest to energy- and resource-efficient domestic wastewater treatment. However, there lack in-depth studies of pretreatment, tests of actual wastewater, and examination of long-term performance. Herein, an upflow nitritation-anammox granular reactor has been investigated to treat primary effluent with a hybrid anaerobic reactor (HAR) as pretreatment for more than 300 days. This system achieved 92% of COD removal, 75% of which was accomplished by the HAR, and had an average final effluent COD concentration of 22 mg L−1. More than 90% of ammonium was removed in the nitritation-anammox reactor, achieving a nitrogen removal rate of 81.0 g N m−3 d−1 in the last stage. The accumulation of sulfate-reducing bacteria in the HAR evidenced the effect of sulfate on COD removal and subsequent nitrogen removal. Anammox bacteria (predominantly Ca. Jettenia asiatica) accounted for up to 40.2% of total granular communities, but their abundance decreased over time in the suspended communities. The dynamics of major metabolisms and functional genes involved in nitrogen conversion were predicted by PICRUSt based on the taxonomic data, providing more insights into the functions of the microbial communities. These results have demonstrated the effectiveness and importance of anaerobic pretreatment to successful mainstream nitritation-anammox.

Combination of Microbubble Catalytic Ozonation and Biological Process for Advanced Treatment of Biotreated Coal Chemical Wastewater

A combination of microbubble catalytic ozonation and biological process was used for advanced treatment of biotreated coal chemical wastewater (BCCW). The performance of the combination system and the influence of the ratio of ozone dosage to influent COD were investigated. The results indicated that the refractory nitrogen-containing aromatics in the BCCW was degraded efficiently by microbubble catalytic ozonation, which resulted in some COD removal, ammonia nitrogen release, and significant improvement of biodegradability. The ozone utilization efficiency was close to 100% and the off-gas ozone did not need to be treated. Sufficient dissolved oxygen (DO) was provided by the microbubble catalytic ozonation for biological treatment without aeration. COD and ammonia nitrogen were removed further in the biological treatment efficiently. Better performance of the combination system was achieved when the system effluent reflux ratio was 30% and the ratio of ozone dosage to influent COD was 0.44 mg·mg-1. In this case, for microbubble catalytic ozonation, the COD removal efficiency was 42.5%, the ratio of ozone consumed to COD removed was 1.38 mg·mg-1, and the ozone utilization efficiency was 98.0%. For biological treatment, the COD removal efficiency was 42.3%. For the combination system, the total COD removal efficiency was 66.7%, the average final effluent COD concentration was 91.5 mg·L-1, and the estimated total ratio of ozone consumed to COD removed was 0.68 mg·mg-1, indicating better technical and economic performance.