Effluent COD Research Articles

Comparative study on phycoremediation performance of three native microalgae for primary-treated municipal wastewater

The current study was aimed to investigate the performance of three native microalgae in primary-treated municipal wastewater with regard to their nutrient removal, water quality improvement for reuse, and in vivo Chl-a -based biomass production. The microalgae species belonged to three different taxonomic classes, namely blue–green blue-green algae Nostoc muscorum , diatom Navicula veneta , and green microalgae Chlorella vulgaris . The comparative phytoremediation potentials of the microalgae species and the consortium were evaluated for 7 days-exponential growth phase employed in the batch systems. The results showed that the interaction between in vivo Chl-a concentration and residual concentration of TN, TP, and COD was notable. COD, TN, and TP treatment efficiencies were in the ranges of (85.7–95.7%), (72–96.9%), and (86.07–99.8%), respectively. The final concentrations of TN, TP, and COD in effluent provided by N. veneta treatment complied with EU Directive 91/271, EU Directive COM (2018)337, and national legislation, whereas the results of C. vulgaris partially complied with these legislations. Concerning the phycoremediation efficiency and the growth characteristic of the monoculture and mixed culture of the native microalgae, it was concluded that the monocultures in most cases were superior to the consortium culture. Diatom N. veneta had the highest growth rate (0.88 ± 0.04 day −1 ), Chl-a-biomass yield (50.45 ± 1.5 mg L −1 ), and removal efficiency (96.9 % TN, 99.8 % TP, 95.7 % COD). The results also reveal that the native species effectively reduce TN, TP, and COD concentrations of wastewater, and the diatom N. veneta may be a strong novel candidate for phytoremediation systems. • Three native microalgae were tested for their removal performances of pollutants in pre-treated municipal wastewater. • In vivo Chl-a fluorescence was significantly associated with the residual concentration of TN, TP, and COD. • Diatom Navicula veneta is a novel candidate in the sustainable bioremediation of municipal wastewater. • Phycoremediated municipal wastewater by diatom fulfilled the limit values of EU Directive 91/271 and EU COM(2018) 337.

Treating performance of a commercial-scale constructed wetland system for aquaculture effluents from intensive inland Micropterus salmoides farm

In intensive inland fish farming, discharge of untreated effluents adversely affects adjacent water bodies and causes water pollution. Thus, it is highly necessary to treat the effluents from inland fish farm. In this study, we built a commercial-scale integrated constructed wetland (CW) system with vertical subsurface flow, and monitored the purifying effect. During fish farming and discharge of effluents periods, the water samples were collected to detected the total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), nitrite nitrogen (NO2--N) and chemical oxygen demand (CODMn). Results showed that the system was stable and significantly improved water quality from fish pond. During the fish farming period, the removal efficiency for TN, TP, NH4+-N, NO3--N, NO2--N, and COD was 24.93–43.72%, 61.92–72.18%, 56.29–68.63%, 56.66–64.81%, 56.42–64.19% and 28.37–42.79%, respectively. Similarly, these parameters were also markedly decreased by the integrated CW system during sewage discharge period, and the average total removal rate for TN, TP, NH4+-N, NO3--N, NO2--N, and COD was 50.24%, 64.48%, 61.36%, 62.65%, 56.16% and 37.32%, respectively. It was worth noting that three key parameters for effluents detection TN, TP and COD values were below the threshold values of water quality of Class II in freshwater sewage discharge standard of China (SCT9101-2007). In conclusion, this study evidently demonstrated that application of CW system was an environmental sustainable sewage treatment strategy in intensive inland fish farming.

Improving wastewater treatment plant performance based on effluent quality, operational costs, and reliability using control strategies for water and sludge lines

As a result of urbanization and population growth, wastewater treatment plants (WWTPs) are experiencing increased influent flow rates, pollutant loads, and stricter standards for effluent quality. Therefore, implementing a control strategy is critical for improving the performance of WWTPs in response to highly variable effluent quality. In this study, different strategies for both water and sludge lines are deployed in WWTP model to control dissolved oxygen and biomass concentration in activated sludge system by manipulating aeration intensity and sludge flow rates. The efficiency of suggested control strategies is evaluated using different performance criteria, including effluent quality indicators, operational costs, and system reliability. The proposed method is applied in a real WWTP located in south of Tehran, the capital of Iran. According to the findings, controlling aeration system and sludge flow rate improve effluent quality and system reliability despite increasing operational costs. In the case of simultaneous control of water and sludge lines, the effluent quality index has improved by 9.3%, while the operational costs have increased by 1%. Moreover, the system reliability based on effluent ammonia, TSS, and COD concentration have increased by 33.4%, 9%, and 12.2%, respectively.

Modeling and simulation of the biological process for treating wastewater with a low COD:N ratio under different dissolved oxygen conditions using an extended ASM2d model

Studies are currently lacking on the reaction mechanism of bacterial biopolymers (extracellular polymeric substances (EPS) and soluble microbial products (SMP)) for biological nutrient removal (BNR) in the activated sludge model No. 2d (ASM2d). Meanwhile, the relationship between biopolymers and BNR under different dissolved oxygen (DO) conditions is not completely clear. Thus, this work presented a modified ASM2d model that combines EPS and SMP (E-S-ASM2d), described in detail the interaction between the different bacteria and biopolymer dynamics in an anaerobic, anoxic, microaerobic and oxic (AAMO) reactor, and simulated the influences of DO on BNR process in low COD:N wastewater and on bacterial biopolymers. In addition, 16S rRNA gene analysis was used to characterize the microbial community dynamics in the AAMO reactor under different DO conditions, thus verifying the necessity of introducing microbial interactions to the E-S-ASM2d model. According to the measurements, the average total nitrogen removal rate of effluent increased 19.4 %, and the average EPS content increased 15.5 % under low DO. According to sensitivity analysis, high sensitivity parameters vary under different DO concentrations (namely 3 mg L−1 and 0.5 mg L−1 DO), which demonstrates the need to determine and separately calibrate these parameters according to DO. Finally, compared with traditional ASM2d model, the correlation likelihood values of E-S-ASM2d model for COD, ammonia nitrogen, total nitrogen and total phosphorus of AAMO effluent increased from 0.622, 0.704, 0.639 and 0.329 to 0.850, 0.894, 0.909 and 0.897, respectively, indicating E-S-ASM2d can significantly improve the simulation of nutrient removal under low influent COD:N.

Treatment of hospital wastewater by electron beam technology: Removal of COD, pathogenic bacteria and viruses

The effective treatment of hospital sewage is crucial to human health and eco-environment, especially during the pandemic of COVID-19. In this study, a demonstration project of actual hospital sewage using electron beam technology was established as advanced treatment process during the outbreak of COVID-19 pandemic in Hubei, China in July 2020. The results indicated that electron beam radiation could effectively remove COD, pathogenic bacteria and viruses in hospital sewage. The continuous monitoring date showed that the effluent COD concentration after electron beam treatment was stably below 30 mg/L, and the concentration of fecal Escherichia coli was below 50 MPN/L, when the absorbed dose was 4 kGy. Electron beam radiation was also an effective method for inactivating viruses. Compared to the inactivation of fecal Escherichia coli, higher absorbed dose was required for the inactivation of virus. Absorbed dose had different effect on the removal of virus. When the absorbed dose ranged from 30 to 50 kGy, Hepatitis A virus (HAV) and Astrovirus (ASV) could be completely removed by electron beam treatment. For Rotavirus (RV) and Enterovirus (EV) virus, the removal efficiency firstly increased and then decreased. The maximum removal efficiency of RV and EV was 98.90% and 88.49%, respectively. For the Norovirus (NVLII) virus, the maximum removal efficiency was 81.58%. This study firstly reported the performance of electron beam in the removal of COD, fecal Escherichia coli and virus in the actual hospital sewage, which would provide useful information for the application of electron beam technology in the treatment of hospital sewage.

Performance and modeling studies of rotating biological contactor for treatment of vegetable oil wastewater

AbstractThis study focuses on a lab‐scale rotating biological contactor (RBC) treating vegetable oil wastewater with high BOD and COD. The fabricated RBC was checked for efficiency in degrading polluted wastewater under different operating conditions. The maximum removal efficiencies for BOD and COD were 95.75% and 89%, respectively. This high removal percentage was obtained with 30% submergence of 10 discs rotating at 8 rpm. For the first time, bio‐kinetic models were applied to the experimental results for vegetable oil wastewater. The best fit was obtained with the modified Stover‐Kincannon and Grau model. The saturation constant (Ks) values were 1.872 and 3.024 g/L/d for BOD and COD, respectively, for the modified Stover‐Kincannon and Grau model. For the Grau second‐order model, the saturation constant was 1.416 and 3.744 g/L/d for BOD and COD, respectively. The predicted effluent BOD and COD values of the modified Stover–Kincannon model fitted almost exactly with the experimental values. This clearly predicts that this model can be best used to predict effluent BOD and COD concentration in a Rotating Biological contactor treating vegetable oil wastewater. The kinetic parameters determined in this study can be used to improve the design and operation of continuous mode RBC systems.

Study on performance of carbon source released from fruit shells and the effect on biological denitrification in the advanced treatment

In order to solve the problem of shortage of carbon source for biological denitrification in advanced treatment of the effluent from secondary treatment of sewage, five kinds of fruit shells (pistachio shell, peanut shell, ginkgo shell, walnut shell and hazelnut shell) were preliminarily selected from eight kinds of fruit shells for experiments of static carbon release and denitrification. The carbon release performance (amount and law of carbon release and biodegradability of released carbon) and denitrification performance of different shells were investigated. Results showed that the peanut shell had the largest amount of carbon release (0.88 mg chemical oxygen demand [COD] g−1) and the highest removal rate of nitrate (NO3−-N) (76.48% ± 4.06%). However, the released carbon could not be fully utilized by denitrifying bacteria, resulting in a (205.90% ± 59.49%) increase in effluent COD compared with influent. The amounts of carbon release of ginkgo nut shell, walnut shell, and hazelnut shell were low (0.45, 0.41, and 0.43 mg COD g−1, respectively). The released carbon could not be used easily by microorganisms. Meanwhile, the contents of degradable aromatic protein and protein-like in dissolved organic matter (DOM) were low. Even the fulvic acid–like with low biodegradability also appeared in the soaking solution of the hazelnut shell. The NO3−-N and total nitrogen aveage removal rates were low in these three fruit shells and showed the removals within the 54.10–57.25% range and 52.21%–54.24% range, respectively. The amount of carbon release of pistachio shell was lower than that of peanut shell. However, the released carbon of the former was more biodegradable than that of the latter. Moreover, the relative molecular mass of DOM was small, and the contents of aromatic protein and protein-like were much higher than those of the four other kinds of fruit shells. The NO3−-N removal rate (71.48% ± 0.98%) of pistachio shell was only slightly lower than that of peanut shell. In conclusion, pistachio shell was the best carbon source for biological denitrification in the advanced treatment.

Characterization of microbial communities in anaerobic acidification reactors fed with casein and/or lactose

Protein-rich agro-industrial waste streams are high in organic load and represent a major environmental problem. Anaerobic digestion is an established technology to treat these streams; however, retardation of protein degradation is frequently observed when carbohydrates are present. This study investigated the mechanism of the retardation by manipulating the carbon source fed to a complex anaerobic microbiota and linking the reactor performance to the variation of the microbial community. Two anaerobic acidification reactors were first acclimated either to casein (CAS reactor) or lactose (LAC reactor), and then fed with mixtures of casein and lactose. Results showed that when lactose was present, the microbial community acclimated to casein shifted from mainly Chloroflexi to Proteobacteria and Firmicutes, the degree of deamination in the CAS reactor decreased from 77 to 15%, and the VFA production decreased from 75 to 34% of the effluent COD. A decrease of 75% in protease activity and 90% in deamination activity of the microbiota was also observed. The microorganisms that can ferment both proteins and carbohydrates were predominant in the microbial community, and from a thermodynamical point of view, they consumed carbohydrates prior to proteins. The frequently observed negative effect of carbohydrates on protein degradation can be mainly attributed to the substrate preference of these populations.Keypoints• The presence of lactose shifted the microbial community and retarded anaerobic protein degradation.• Facultative genera were dominant in the presence and absence of lactose.• Substrate-preference caused retardation of anaerobic protein degradation.

Efficient Removal of Organic Matter from Biotreated Coking Wastewater by Coagulation Combined with Sludge-Based Activated Carbon Adsorption

Coagulation–adsorption can be effective in the removal of the organic matters remaining in biotreated coking wastewater (BTCW), and cheap and efficient adsorbents benefit the widespread application of this technology. In this study, a sludge-based activated carbon (SAC) was prepared using zinc chloride to activate sludge pyrolysis carbon for the treatment of BTCW with coagulation as the pretreatment process. According to Brunauer-Emmett-Teller (BET) and the scanning electron microscope (SEM) analysis, the SAC exhibited a specific surface area of 710.175 m2/g and well-developed pore structure. The removal characteristics of the organic matter in BTCW were systematically studied. The results show that 76.79% of the COD in the BTCW was removed by coagulation combined with SAC adsorption, and the effluent COD was below the discharge limit (80 mg/L) (GB16171-2012), with the optimal dosages of polyaluminum chloride and SAC being 150 mg/L and 4 g/L, respectively. Compared with a commercial powdered activated carbon (PAC) (48.26%), the SAC achieved a similar COD removal efficiency (47.74%) at a higher adsorption speed. The removal efficiencies of the hydrophobic components (77.27%) and fluorescent components by SAC adsorption were higher than those by PAC adsorption. The SAC also had an excellent removal effect on complex organic compounds and colored substances in the BTCW, as revealed by UV-vis spectra analyses.

Evaluating the Performance of Small Wastewater Treatment Plants

An evaluation of the treatment performance of small wastewater treatment plants with the capacity of ≤50 PE (population equivalent) was carried out using data collected in external monitoring reports, taking Upper Austria as an example. External monitoring data for 2009–2018 were available for this analysis. About 2′500 small WWTPs are in operation in Upper Austria. The main technologies implemented include about 870 Sequencing Batch Reactor (SBR) plants, 630 conventional activated sludge (CAS) plants and 535 vertical flow (VF) wetlands. The data set for the present evaluation comprises a total of approx. 14′000 external monitoring reports from approx. 2′000 small WWTPs. This paper presents the results of this evaluation. The evaluation showed that all technologies meet the legal requirements regarding BOD5, COD and NH4-N effluent concentrations. However, for small WWTPs with a polishing stage consisting of a VF wetland, the median values of the effluent concentrations and the limit value exceedances are significantly lower. There is no evidence of a significant deterioration in treatment performance with the age of the plant for any technology. However, for all technical WWTPs such as SBR and CAS plants, a greater fluctuation of the measured values (i.e. the median values of the effluent concentrations) can be observed when the plant is longer in operation. Compared to technical WWTPs, this fluctuation is significantly smaller in VF wetlands.

Successional dynamics of low C/N activated sludge system under salinity shock: Performance, nitrogen removal pathways, microbial community, and assembly

Limited carbon (low C/N) and salinity stress affect the stability of wastewater treatment plants. However, the effect of salinity shock on activated sludge systems with low C/N ratio wastewater remains unclear. An anaerobic/aerobic/anoxic sequencing batch reactor treating low C/N wastewater was established to investigate the effects of salinity shock on system performance, nitrogen removal pathways, microbial community, interactions, and assembly. The results showed that the effluent COD concentration could maintain a stable level, and the average COD removal efficiency was 94.9%. However, total nitrogen removal was significantly inhibited. With the addition of salinity, efficiencies of total nitrogen removal and simultaneous nitrification and denitrification decreased from 91.4 to 73.8% to 86.7 and 39.7%, respectively; however, nitrite reduction capacity increased by 25.4%. After removing salinity, ammonia oxidation capacity further deteriorated, evidenced by the increase in effluent NH4+-N from 8.0 to 11.8 mg/L. During the salinity shock, partial nitrification became the main nitrogen removal pathway because of the inhibition of Nitrospira and high nitrite accumulation ratio (>99.0%). Molecular ecological network analysis indicated that increased competition, decreased total modules, and disappearance of keystone taxa were related to the deterioration of ammonia oxidation capacity and simultaneous nitrification and denitrification. Moreover, the abundant denitrification module and increased denitrifiers contributed to the increase in nitrite reduction capacity. Salinity shock under low C/N conditions resulted in a stronger stochastic community assembly. This study provided information that can help enable stable operations for treating low C/N wastewater.

Constructed Wetland Tipe Horisontal Subsurface Flow Menggunakan Rumput Odot untuk Pengolahan Efluen IPAL Tahu

The effluent of tofu’s anaerobic digester contains organic matter and require further treatment. Constructed wetland (CW) using forage grass plant is one of the alternatives. The study is aimed to observe the effect of CW’s stage variation and planting duration on TSS and COD effluent. Plant growth also observed duringoperation. Two CWs horizontal subsurface tank of dimension 100 cm x 50 cm x 50 cm were arranged in series as stage 1 and 2. Tank was planted with Pennisetum purpureum c.v Mott at spacing of 25 cm, tank without plants as control, and operated at hydraulic loading rate of 0.1 m3/m2.day. Temperature, pH and plant height was measured every 2 days, TSS and COD every 1-2 week. The study showed, there was relatively no temperature difference between control and planted CW. The pH effluent increased with the pH of stage II being higher than stage IThe TSS and COD removal efficiency in planted CW was 61-90 % and 27-85 %, while for control was 8-85 % and 13-79 %, respectively. Plant can grow, indicated by the addition of plant height and plant weight during harvesting. In conclusion, CW stage and planting duration had effect on TSS and COD effluent.

BIOTRANSFORMATION OF WASTEWATER PRODUCTION OF BAKERY YEAST WITH BIOGAS GENERATION

Baking yeast enterprises are a source of environmental pollution by concentrated wastewater. They are usually diluted with water and discharged into sewerage. It is rational to use methane fermentation, which will ensure the removal of pollutants and make the process cost-effective through the use of biogas and digestion. Therefore, it is relevant to study the question of the influence of fermentation parameters on the cleaning efficiency. The aim of the work is to study the methane fermentation of yeast production effluents in a continuous mode. Objectives: analysis of solving the problem of wastewater treatment of yeast plants, study of the influence of process parameters (dilution rate, addition of cobalt salts) on the efficiency of treatment; gas generation; vitamin production. Initial COD of effluents 4500 mg O2/dm3, pH 6. Cultivation regime – continuous, dilution rate 4,1·10–3, 6,2·10–3, 8,2·10–3, 12,4·10–3 hours–1. Cleaning efficiency 78,9 %. High values ​​of dilution rate cause overload of activated sludge, which leads to reduced cleaning efficiency. The presence of cobalt also has a depressant effect. A significant amount of biogas (up to 5,2 dm3/dm3) is produced with a high content of methane (up to 85 %), which is an alternative fuel. As the dilution rate increases, the biogas and methane content decrease. With increasing dilution rate from 4,1·10–3 to 12,4·10–3 hours–1, biogas decreased from 1,11 to 0,94 dm3/g CODloading, and from 1,43 to 1,39 dm3/g CODfermentation. Similarly to the effect on the depth of purification, the inhibitory effect of cobalt on methanogeneration is observed. Digestion is a valuable fertilizer with a significant content of cobalamin vitamins (up to 95 μсg/g). The addition of cobalt salts stimulates the synthesis of vitamins, providing an increase of 26,7 to 51,6 %, improving the ratio between active and inactive forms.

Denitrification performance and characteristics of untreated corncob for enhanced nitrogen removal of municipal sewage with low C/N ratio

Unpretreated corncob was applied in denitrification bio-filter (DNBF) and anoxic tank of AAO system, respectively, to treat sewage with low C/N ratio, and both two approaches achieved good denitrification performance. Although shorter HRT could effectively decrease effluent chroma and COD of corncob-DNBF, nitrogen removal efficiency declined unexpectedly. Higher internal reflux ratio was beneficial for corncob-AAO without damage to anoxic environment for denitrification, while there was no risk of effluent chroma and excessive COD. Different supplement modes could realize same denitrification effect with distinct advantages, which were higher specific denitrification rate and biomass amount, respectively. The latter mode, applying corncob at secondary treatment, was preferable for its operational stability and convenience. Stoichiometry analysis indicated the unit COD demand of AAO decreased from 5.70 to 5.04 g COD/g N after adding corncob, and the oxygen demand (or energy consumption of aeration) decreased as well. The dominant substrates decomposer in corncob-AAO altered to Kouleothrix (affiliated to phylum Chloroflexi), and the main denitrifying bacteria were unclassified_f__Methylophilaceae and Azospira. Accordingly, functional enzymes for degrading glucan, xylan and lignin and processing denitrification showed satisfying abundance in the integrated system, especially in the newly formed biofilm.

Influence of Aquatic Plants and Flow Rate on Physico-chemical Characteristics of Sewage Effluent Treated through Constructed Wetland Technology

Aims: To evaluate the influence of aquatic plants and flow rate on physico-chemical properties of sewage effluent with constructed wetland technology.
 Study Design: Randomized block design
 Place and Duration of Study: Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore - 03 and June 2020 – Dec 2020
 Methodology: Constructed wetland (CW) model was designed and three different aquatic plants viz., Canna indica, Arundo donax, and Xanthosoma sagittifolium were used for the study. Two different flow rates viz., 5ml/min and 10 ml/min were compared for assessing their influence in treating sewage effluent in the constructed wetlands. 
 Results: Among the aquatic plants, the pollutants like BOD, COD,TDS and TSS in the sewage effluent were declined and found to be 320, 1220, 666, 22 mg L-1 in Canna indica and 340, 1380, 866, 36 mg L-1 in Xanthosoma sagittifolium and 340, 1380, 866, 36 mg L-1 in Typha angustifolia utilized treatments at flow rates 5 ml/min respectively during 7th day retention time. Similar decreasing trend was observed in BOD, COD, TDS and TSS of the sewage effluent at flow rates of 10 ml/min.
 Conclusion: Based on the study, it was evident that constructed wetland (CW) with Canna indica, Xanthosoma sagittifolium and Typha angustifolia found to perform better under flow rate of 5 ml/min for treating sewage effluent at the retention time of 7 days.

Comparison of COD and TOC in influents and effluents of six industrial wastewater treatment plants in Korea

Objectives : This study compared the CODMn and TOC concentrations of the influent and effluent from six industrial wastewater treatment plants (WWTPs) and the wastewater from manufacturing facilities in the industrial complexes, and to understand the correlation between the two indicators.Methods : The sampling campaigns were performed four times at each WWTP for both influent and effluent. Water quality surveys were also conducted to assess the characteristics of organic matter in the wastewater from the manufacturing facilities. A total of 272 facilities including manufacturing, non-manufacturing, and miscellaneous manufacturing units were surveyed. Results and Discussion : The CODMn/TOC ratios of the influent and the effluent of the WWTPs ranged from 0.78 to 1.79 (average 1.19) and 0.94 to 1.58 (average 1.20), respectively. The ratio of CODMn/TOC ratio in the wastewater from the manufacturing facilities was 1.06~1.22 (average 1.12). Industries with high R2 values for the CODMn/TOC ratios included rubber and plastics manufacturing (CODMn/TOC = 1.17), nonferrous metals manufacturing (CODMn/TOC = 0.94), medical materials and pharmaceutical manufacturing (CODMn/TOC = 0.98), and chemicals manufacturing (CODMn/TOC = 1.27).Conclusion : CODMn/TOC ratios of the influent and effluent of the six plants and the wastewater from manufacturing facilities varied in different ranges for each WWTP, with an average value of 1.12. The results of this study can be used as basic information to manage the effluent water quality of the WWTPs.

Cake layer reformation rates on self forming dynamic membranes and performance comparison with microfiltration membranes

Dynamic membranes (DMs) keep on attracting attention progressively as an alternative to conventional membranes because they can be operated with relatively higher fluxes and lower fouling rates. However, there are many factors affecting the performance of DMs, such as DM pore size, structure, and operating conditions. In this study, mainly focused on the investigation of cake formation rates both in initial formation and reformation rates after physical/chemical cleaning. In this context, it has been evaluated the performances of DMs with different pore sizes (171 μm, 90 μm, and 30 μm) and different structures under the same conditions and compared their performances with microfiltration (MF) membranes (0.45 μm and 0.22 μm) in a single reactor. In the study, the effects of different fluxes (15-, 20-, 25 L/m2·h (LMH), SADm (1-, 0.8-, 0.5 m3-air /m2·h) and F/M (0.095, 0.125, 0.19 g-COD/g-MLSS·day) conditions on the treatment and filtration performance of DMs were investigated. High COD (>95%) and turbidity (<10 NTU) removals were obtained in this study. In particular, the 30 μm DM (0.65 ± 0.47 NTU) produced quite close effluent turbidity compared to MFs (0.12 ± 0.05 NTU). Low SADm and high F/M values resulted in increased effluent COD concentrations and turbidity values. By decreasing the SADm, the cake formation rate and the fouling rate increased, which showed that there is a definite relationship between the cake formation rates and the fouling rates. Additionally, considering all the results, the most stable operation was obtained in the 30 μm DM, although it has been occurred the least fouling in the 90 μm membrane in the study. This study, focused on cake reformation rates, attempts to show that DMs can be used as an alternative to MBRs. Especially, when taking into account the results of the reformation rate of 30 μm DM (6.09 NTU/h) and other high filterability features.

Experiments and adaptive-network-based fuzzy inference system modelling in a hybrid up-flow anaerobic sludge blanket reactor to assess industrial azadirachtin effluent quality

Experimental investigations were carried out for the treatment of industrial azadirachtin effluent in a hybrid up-flow anaerobic sludge blanket (HUASB) reactor continuously for 115 days in three stages at mesophilic temperature (30 − 35˚C). An adaptive-network-based fuzzy inference system (ANFIS) modelling and statistical regression analysis were applied with the raw data. In the ANFIS modelling as well as in the statistical regression analysis, the operating parameters such as initial pH, influent COD, effluent COD and biogas generation (X1, X2, X3 and X4) were taken as variables and effluent BOD values as a response (Y). The average percentage error (APE) values of ANFIS modelling were 2.18, 12.29, and 0.01%, for stage-I, II and III respectively. These values indicated that ANFIS modelling performed well in all the three stages and provided more accurate results.

Thermophilic anaerobic membrane bioreactor for pulp and paper primary sludge treatment: Effect of solids retention time on the biological performance

Lignocellulosic biomass is a promising renewable feedstock for the production of bioenergy and platform chemicals; however, its use would not be economically viable without adopting effective transformation technologies. In this work, long-term anaerobic treatment (370 days) of pulp and paper primary sludge (PS) was performed by a thermophilic anaerobic membrane bioreactor (AnMBR) for the first time to investigate the effect of various solid retention times (SRTs) on biogas production and solids reduction ratios. The tested STRs (32–55 days) have shown varying biogas productivity, and it can be concluded that the longer the SRT, the higher is the biogas yield. At the optimum solids retention time of 55 d, an organic loading rate of 2.15 ± 0.10 kg-TSS/L.d, and hydraulic retention time of 5 d, average biogas yield of 106.4 ± 8.5 m3 biogas/tonne TSS added (approximately 72.7 m3 CH4/t VSadded) was achieved with an average methane content of 56 ± 4% and the solids reduction ratio ranged between 47% and 54.9%. Besides biogas yield, the quality of the permeates, solids reduction, and digestates characteristic/dewaterability changed by changing the SRT. The mixed liquor suspended solids concentrations and solids reduction increased with increasing SRT, while the effluent COD concentration and sludge dewaterability decreased. The Fourier Transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) findings exhibited that the digestate contains more lignin and cellulose than the other substances, while the nitrogen and carbon concentration decreased with increasing SRT.

Anaerobic treatment of sugarcane vinasse pretreated with a calcium-based biopolymer

This study investigated the influence of a previous sugarcane vinasse coagulation, by using a calcium-based biopolymer, on anaerobic treatment in a lab-scale reactor. Two anaerobic reactors (R1 and R2) were operated for 155 days. R1 was fed only with raw sugarcane vinasse and R2 was fed with pretreated effluent. The operation was divided into three stages: E1 (inoculation and adaptation); E2; and E3. The major difference between E2 and E3 was the fact that R2 failed at the end of E2. Thus, R2 was recovered by applying a low organic loading rate (OLR) of raw vinasse for 29 days. In E2 and E3, for both reactors, pH, alkalinity, COD (influent and effluent samples), and methane production were monitored. During E1, an OLR of 2.0 kgCOD. m-3.d-1 1 was applied, and R1 and R2 sludges showed good adaptation to the wastewater in this condition. Then, the OLR was progressively increased to 7.0 kgCOD.m-3.d-1 in both systems. The average COD removal efficiencies were 82.9 ± 4.4% and 72.2 ± 18.1% for R1 and R2, respectively. R2, operated with pretreated vinasse, showed a decrease in the COD removal and methane production, which could be caused by the biopolymer presence. The average COD removal efficiencies in E3 were 77.5 ± 9.4% and 79.2 ± 9.7% for R1 and R2, respectively. After 155 days of operation, a decrease in the COD removal and methane production was identified again in R2, indicating a new failure. The quality of sludge granules from the inoculum and also from the granules developed at the end of R1 and R2 operation was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). These analyses indicated a rise in the rugosity of R1 and R2 granules, possibly due to the deposition of sedimentable compounds present in both raw and pretreated vinasse. The EDS analyses indicated a high presence of calcium in R2 granules, indicating that this compound acted in the reduction of mass transfer between organic load from vinasse and the granules’ microbiota.