Aerobic Sequencing Batch Reactor Research Articles

Chloroxylenol positively affects the aerobic sequencing batch reactor performance and reshapes microbial communities and antibiotic resistance genes

The antibacterial ingredient chloroxylenol (PCMX) has been frequently detected in various environments, raising increasing concerns about its potential risks to organisms and ecosystems. Herein, the impacts of PCMX on the performance and microbial communities of aerobic sequencing batch reactors were investigated. The results demonstrated that 0.1 and 1.0 mg/L PCMX did not affect the removal performance of COD and NH4+-N, as well as the production of extracellular polymeric substances. However, a notable enhancement in these performances was observed when the concentration of PCMX reached 10 mg/L. Analysis of microbial community revealed that exposure to PCMX did not alter α diversity but significantly shifted the community structure. Spirosoma and Ferruginibacter were identified as dominant genera across all stages in the sludge, with Ferruginibacter being inhibited by 10 mg/L PCMX (from 20.3 % to 11.1 %). Network analysis revealed that PCMX had a diminishing effect on the interaction and complexity of microbial. High throughput qPCR analysis indicated that PCMX reshaped the antibiotic resistance genes (ARGs). The relative gene copy number increased from 0.23 to 0.29 at a concentration of 0.1 mg/L PCMX, while it decreased from 0.51 to 0.40 by 10 mg/L PCMX. Genes tetX and sul2 were identified as dominant genes unaffected by 0.1 and 1.0 mg/L but significantly inhibited by 10 mg/L PCMX. These findings suggested that environmental levels of PCMX might promote the enrichment of ARGs, while higher concentrations impeded gene propagation. This study provides new information regarding the roles, potential risks, and removal strategies of PCMX in wastewater treatment processes.

Comparison of aerobic and anoxic-oxic sequential batch reactors for treating textile wastewater

ABSTRACT The discharge of untreated textile dyeing wastewater containing azo dyes has significant ecological consequences. The incomplete biodegradation of these dyes can produce harmful and carcinogenic aromatic amines (AAs), which pose a threat to the environment. This study evaluates the treatment of real textile dyeing wastewater containing azo dyes by two different systems: an anoxic sequential batch reactor (A/O-SBR) and an aerobic sequential batch reactor (A-SBR). The effects of hydraulic retention time (HRT) on both systems were investigated in terms of chemical oxygen demand (COD), total nitrogen (TN), color, and AAs removal. Ranging between 85% and 92%, the COD removal efficiency was almost similar in the A/O-SBR and A-SBR systems, suggesting that the aerobic phase is primarily responsible for COD removal. However, A/O-SBR showed higher removal of color (90%) than A-SBR (75%) due to the presence of an anoxic phase. HRT has a significant impact on color removal in both systems. However, there was no significant effect on COD removal when HRT exceeded 12 h. According to LC-MS/MS analysis, increasing the HRT from 12 h to 24 h increased the AAs concentration in the anoxic phase, from 253 ng/L to 261 ng/L and slightly decreased the AAs concentration in the aerobic phase from 107 ng/L to 102 ng/L. This resulted in an overall improvement in both dye and AAs removal. The presence of aerobic phase in A/O-SBR and A-SBR demonstrates strong AAs removal capacity. GC-MS/MS analysis indicated that as the HRT of A/O-SBR and A-SBR increased, the number of by-products increased.

Evaluating the Effect of Nonaerobic Hydraulic Retention Time on Nutrients Removal in Nonaerobic and Aerobic SBR

The nonaerobic stage is critical for the processes of denitrification and phosphorus release in biological wastewater treatment. A lab-scale sequencing batch reactor (SBR) operating as nonaerobic/aerobic was used to treat synthetic wastewater, and the nutrients removal performance was investigated under different nonaerobic hydraulic retention times (HRTs). The results showed when the nonaerobic HRT changed from 0 to 4 h with constant aerobic HRT of 8 h [dissolved oxygen (DO) 0.50–1.50 mg·L−1], the removal efficiencies of PO43−─P and NH4+─N were all above 90.00%, respectively. The nonaerobic HRT could influence carbon utilization between denitrification and phosphorus release, which showed a close relationship with the ratio of consumed chemical oxygen demand (COD)phosphorus release to CODdenitrification (0.94). Specifically, the consumed CODphosphorus release increased with the increase of nonaerobic HRT (0.90), whereas the relationship between consumed CODdenitrification and nonaerobic HRT was limited (−0.60). Furthermore, internal carbon source produced through phosphorus release could promote simultaneous nitrification denitrification. This control strategy could be conveniently applied in intermittent-flow sewage treatment plant through adjusting nonaerobic HRT.

Biosorption and biotransformation behaviours of veterinary antibiotics under aerobic livestock wastewater treatment processes

To study the fate of veterinary antibiotics released from swine wastewater treatment plants (SWTP), 10 antibiotics were investigated in each unit of a local SWTP periodically. Over a 14-month period of field investigation into target antibiotics, it was confirmed that tetracycline, chlortetracycline, sulfathiazole, and lincomycin were used in this SWTP, with their presence observed in raw manure. Most of these antibiotics could be effectively treated by aerobic activated sludge, except for lincomycin, which was still detected in the effluent, with a maximum concentration of 1506 μg/L. In addition, the potential for removing antibiotics was evaluated using lab-scale aerobic sequencing batch reactors (SBRs) that were dosed with high concentrations of antibiotics. The SBR results, however, showed that both sulfonamides and macrolides, as well as lincomycin, can achieve 100% removal in lab-scale aerobic SBRs within 7 days. This reveals that the potential removal of those antibiotics in field aeration tanks can be facilitated by providing suitable conditions, such as adequate dissolved oxygen, pH, and retention time. Furthermore, the biosorption of target antibiotics was also confirmed in the abiotic sorption batch tests. Biotransformation and hydrolysis were identified as the dominant mechanism for removing negatively charged sulfonamides and positively charged antibiotics (macrolides and lincomycin) in SBRs. This is due to their relatively low sorption affinity (resulting in negligible to 20% removal) onto activated sludge in abiotic sorption tests. On the other hand, tetracyclines exhibited significant sorption behavior both onto activated sludge and onto soluble organic matters in swine wastewater supernatant, accounting for 70%–91% and 21%–94% of removal within 24 h, respectively. S-shape sorption isotherms with saturation were observed when high amounts of tetracyclines were spiked into sludge, with equilibrium concentrations ranging from 0.4 to 65 mg/L. Therefore, the sorption of tetracyclines onto activated sludge was governed by electrostatic interaction rather than hydrophobic partition. This resulted in a saturated sorption capacity (Qmax) of 17,263 mg/g, 1637 mg/g, and 641.7 mg/g for OTC, TC, and CTC, respectively.

Seeding and Acclimatization for Aerobic Processing of Restaurant Wastewater with Sequencing Batch Reactor

Restaurant wastewater has a relatively high organic matter content, so it needs to be treated to meet the specified quality standard. One of the technologies that can be used in restaurant wastewater treatment is Sequencing Batch Reactor (SBR) technology. The purpose of this study is to set up an aerobic SBR system with seeding and acclimatization treatments to reduce the amount of organic matter in restaurant wastewater when a shock load occurs. The research was done using wastewater from a restaurant in Bandung and activated sludge from the food industry in Bogor as seeds for microorganisms. In this study, the seeding process was carried out by introducing 25% activated sludge and 75% nutrients into the reactor, and the acclimatization process was carried out by introducing a specific ratio of nutrients and wastewater into the reactor gradually until the waste concentration reached 100%. The parameters tested were COD, MLVSS, DO, pH, and temperature. During the seeding procedure, the initial COD value of 3,200 mg/L declined. It began to stabilize on the seventh day, with a COD value of 1,080 mg/L. The COD removal reached a relatively stable condition in the acclimatization process starting on day 2, where COD decreased from the original 1,280 mg/L to 480 mg/L.

Integrated sonophotocatalytic oxidation and SBR processes for the effective treatment of antibiotics with an emphasis on process optimization and microbial diversity

The presence of antibiotics in water and wastewater is a serious environmental concern of emerging interest globally. Their effective removal with a single treatment process is, however, challenging because of their widely varying characteristics, and requires innovative integration of treatment processes. In this study, sonophotocatalytic oxidation process was integrated with an aerobic sequencing batch reactor (SBR) for the comprehensive removal of a mixture of antibiotics. Initially, a Central Composite Design using Response Surface Methodology was used to optimise the operational parameters, viz. ultrasound (US) frequency, pH, and catalyst dosage, for the removal of Ciprofloxacin (CPX), Amoxicillin (AMX), and Tetracycline (TTC) in simulated wastewater. An optimised condition of 20 kHz US frequency, 6.59 initial pH, and 0.94 g L−1 catalyst dosage was observed for the maximum pollutant removal. These experimental conditions were subsequently used for combined sonophotocatalysis-aerobic SBR treatment. Three SBR systems representing a control system, pre-treated system, and untreated system, were used for the study. All three systems were able to achieve an average COD and NH4+-N removal of 85 % and 98 %, respectively. Results from the biological systems concluded that an enhanced CPX and TTC removal was observed in the pre-treated system, whereas maximum AMX removal was observed in the untreated SBR system. The metagenomic analysis confirmed the significant difference of microbial species with the addition of pretreated and untreated wastewater into the biological reactor, and pretreated system having higher number of species and greater biodiversity in comparison to untreated system.

Removals of endocrine disrupting compounds during landfill leachate treatment in two-stage aerobic sequential batch reactor: Effect of Alcaligenes faecalis no.4 bio-augmentation

The effect of Alcaligenes faecalis no.4 (A. faecalis no.4) in two-stage sequencing batch reactor (SBR) treatment of endocrine disrupting compounds (EDCs), i.e., bisphenol A (BPA), di-n-butyl phthalate (DBP) and bis-2-ethyl hexyl phthalate (DEHP) containing in landfill leachate was investigated. Two aerobic SBRs were operated without (C-SBR) and with A. faecalis no.4 bio-augmentation (B-SBR) at a hydraulic retention time (HRT) and solid retention time (SRT) of 3 and 30 days over 280 days. The removals of BPA, DBP, and DEHP were significantly improved to 91.1%, 84.5%, and 80.9% from their average influent concentrations of 185, 244, and 532 μg/l under the presence of A. faecalis no.4 through their enhanced biodegradation. The A. faecalis no.4 bio-augmentation helped promote a strong consortium of bacterial genera reported as BPA, DBP, and DEHP degraders in microbial sludge. This study demonstrated the technical feasibility of applying SBR with A. faecalis no.4 in landfill leachate treatment with effective EDC removals.

Long-term performance study applying a tandem AnSBR-ASBR to treat wastewater containing N, N-dimethylformamide: Sludge physicochemical properties, microecology, and functional genes

The effective treatment of industrial pollutant N, N-dimethylformamide (DMF) containing wastewater is a matter of worldwide concern. This study investigated the performance and microecology of anaerobic granular sludge (AGS) and aerobic sludge (AS) in treating DMF wastewater. It was also explored the degradation pathways of DMF in an anaerobic sequencing batch reactor series aerobic sequencing batch reactor (AnSBR-ASBR). Results showed that 5 mg/L DMF facilitated the degradation of chemical oxygen demand (COD) by AGS with AS, while 100 mg/L DMF reduced the efficiency of AS. The physicochemical properties of the sludge showed that the polysaccharide and protein levels in extracellular polymeric substances and key enzyme activity (acetate kinase, coenzyme F420) deteriorated when DMF increased from 25 to 100 mg/L. As the DMF dose increased (0–100 mg/L), the Euryarchaeota abundance in the AGS decreased from 28.41% to 11.06%, and the predominant methanogenic pathway shifted from a combination of aceticlastic methanogenesis (AM) and hydrogenotrophic methanogenesis (HM) to HM. The metabolic pathway to effectively remove DMF was as follows: hydrolysis of DMF to dimethylamine, methylamine, and finally mineralisation to CO2. The abundance of dmd-tmd, a functional gene encoding dimethylamine/trimethylamine dehydrogenase, increased as the DMF increased in the AS. This study systematically examined the operating efficiency and stability of the AnSBR-ASBR, and summarized the AGS and AS stress response, microbial community evolution, key metabolic pathways to DMF, also provided useful information for the treatment of industrial wastewater containing DMF.

Treatment of Mixed Azo Dyes in an Aerobic Sequential Batch Reactor and Toxicity Assessment Using Vigna radiata

Azo dyes are the most widely used dyes in the textile industry due to their stability, but their redundancy to degradation is of significant concern, particularly to aquatic ecosystems. In the present study, a lab-scale aerobic sequential batch reactor (SBR) was operated to analyze the degradation of mixed reactive azo dyes at a concentration of 100–1000 mg/L. The chemical oxygen demand (COD) removal increased from 34% to 61.15% and then dropped to 21.16% at the highest used concentration. The biochemical oxygen demand (BOD) removal decreased from 63% to 55.55% to 28.14% with an increasing dye concentration. The biosorption experiment and dried activated sludge (DAS) successfully removed about 0.300 mg of dyes by absorption within 2 hours. A toxicity assessment was carried out by employing a phytotoxicity test on Vigna radiata. The percentage of germination was used to detect the toxic effects of untreated dye-containing wastewater on plant growth. The treated wastewater showed 100% germination compared to 70% in untreated wastewater containing 100 mg/L mixed dyes, confirming the treatment’s efficacy.

Investigation of the effect of nitrification inhibition on the performance and effluent quality of aerobic sequential batch reactors.

The use of nitrification inhibition as a concentrating step for ammonium (NH4+), for the purpose of increasing the potential for simultaneous recovery of phosphate (PO43-) and NH4+ from effluent streams of an aerobic sequencing batch reactor (SBR) system, has never been investigated in the literature. Therefore, the present study aimed to determine the effect of the inhibition of nitrification on both the reactor performance and effluent quality in a laboratory scale aerobic SBR system. In order to compare the observed results, a separate reactor, where the inhibition was not applied, was operated as a control reactor (CR) under the identical operational conditions used for the inhibitory reactor (IR). Experimental results for the reactor performance showed that effluents with low total suspended solids (< 50mg/L) and chemical oxygen demand concentrations (> 90% of removal efficiency based on the influent concentration of 500mg/L) were achieved for both SBRs by obtaining an activated sludge with a sludge volume index < 60mL/g after the acclimation period. In the same period, the effluent PO43-, NH4+, and nitrate (NO3-) concentrations were found to be 17.0 ± 4.0, 1.26 ± 0.84, and 21.5 ± 39mg/L for the CR and 10.0 ± 4.4, 3.9 ± 2.4, and 9.2 ± 1.5mg/L for the IR, respectively. During this period, 94% of the removed NH4+ (NH4+rem.) was converted to NO3- in the CR, indicating almost complete nitrification occurred in the reactor. However, only 47% of the NH4+rem. was converted to NO3- in the IR as a result of the inhibition of nitrification, meaning a partial inhibition (53%) occurred due to the inhibition treatment. These results clearly demonstrated that the inhibition of nitrification allowed the effluent NH4+ concentrations to increase by suppressing the formation of NO3- ions. Based on the results, it can be concluded that inhibition of nitrification in an aerobic SBR system creates a potential for conserving the effluent NH4+ concentration and increasing consecutive recovery of PO43- together with NH4+ from the effluent discharges.

Sequencing Batch Reactor Performance Evaluation on Orthophosphates and COD Removal from Brewery Wastewater

The discharge of industrial effluent constituting high orthophosphates and organic pollutants in water receiving bodies compromises freshwater quality and perpetuates eutrophication. In this study, an anaerobic–aerobic sequencing batch reactor (SBR) under activated sludge was investigated for orthophosphates and chemical oxygen demand (COD) removal from brewery wastewater. Raw brewery wastewater samples were collected on a daily basis for a period of 4 weeks. The findings of the study are reported based on overall removal efficiencies recording 69% for orthophosphates and 54% for total COD for a sludge retention time (SRT) of 7 days and hydraulic retention time of 18 h at mesophilic temperature conditions of ±25 °C. Moreover, the SBR system showed stability on orthophosphate removal at a SRT ranging from 3 to 7 days with a variation in organic volumetric loading rate ranging from 1.14 to 4.83 kg COD/m3.day. The anaerobic reaction period was experimentally found to be 4 h with the aerobic phase lasting for 14 h. The SBR system demonstrated feasibility on orthophosphates and COD removal with variation in organic loading rate.

Impact of perfluorooctanoic acid on treatment wastewater by a tandem AnSBR-ASBR system: Performance, microbial community and metabolism pathway

The interaction of perfluorooctanoic acid (PFOA) with anaerobic and aerobic microorganisms was investigated to explore the effect of PFOA on microbial community evolution, carbon metabolism and nitrogen metabolism, and to a provide reference for treatment of wastewater containing PFOA. Compared with phase I (PFOA 0 mg L−1), the average COD removal rate of the anaerobic sequencing batch reactor (AnSBR) in phase II, III and IV (5–20 mg L−1) decreased by 8.85%, and that of the aerobic sequencing batch reactor (ASBR) decreased by 8.31%. However, PFOA had little effect on ammonia nitrogen (NH4+-N) removal at the preset concentrations and the average removal rate of NH4+-N in the system was 97.90 ± 0.59%. The average removal of PFOA in the AnSBR and ASBR decreased from 78.30% and 86.36% (phase I), to 18.77% and 19.25% (phase IV), respectively, indicating that the removal of PFOA was mainly dependent on the adsorption of microorganisms in the initial the experiment. 3D excitation-emission matrix results showed that PFOA affected the functional groups of extracellular polymeric substances, especially the red shift of fulvic acids along the Em axis. Meanwhile, high concentration PFOA could reduce the activities of acetate kinase and coenzyme F420 in the sludge, thereby affecting the metabolism of carbon and methane by microorganisms. When the concentration of PFOA was 20 mg L−1, the abundances of hydrogenotrophic methanogens such as Methanospirillum (AnSBR phase I-IV: 24.07%−27.43%) and Methanobacterium (AnSBR phase I-IV: 15.06%−21.27%) exceeded that of methylotrophic methanogens, indicating that the existence of PFOA changed the methane metabolism pathway.

Coupling of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor

ABSTRACT The performance of endogenous/exogenous nitrification and denitrification in an aerobic granular sequencing batch reactor was investigated for treating inorganic wastewater with ammonia nitrogen of 250 mg/L. The sequencing batch reactor with an effective volume of 120.5 L was started by seeding autotrophic nitrifying granular sludge (ANGS) and operated under oxic (110 min)/anoxic (120 min)/oxic (110 min) aeration mode. The total inorganic nitrogen (TIN) removal efficiency of ANGS was between 60% and 70% without external carbon sources in days 1–25. However, the operation mode was unsustainable as endogenous nitrification and denitrification would lead to an obvious decrease of sludge concentration. After sodium acetate (the contributed chemical oxygen demand in the reactor was 250–300 mg/L) was added at the beginning of the anaerobic/anoxic stage from day 26, aerobic granules were inadaptable in a few days, which resulted in particle disintegration and SVI increase. As microbes gradually acclimated to the new environment, the aerobic granular sludge became smoother and denser, the relative abundance of denitrifying bacteria increased to 66.07%, and the removal efficiency of TIN gradually increased to more than 90% from day 89. Contributions of endogenous/exogenous nitrification and denitrification to TIN removal were 54.09% and 46.01%, respectively. The coupling of endogenous/exogenous nitrification and denitrification could reduce the aeration consumption, save the external carbon source dosage and decrease the alkalinity consumption, which provided another option for treating wastewater from ionic rare earth mine.

Enhanced biological phosphorus removal in low-temperature sewage with iron-carbon SBR system

ABSTRACT This study proposed an AO-SBR (Anaerobic Aerobic Sequencing Batch Reactor) combined with iron-carbon micro-electrolysis (ICME) particles system for sewage treatment at low temperature and explored the dephosphorisation mechanism and microbial community structure. The experimental results illustrated that ICME particles contributed to phosphorus removal, metabolic mechanism of poly-phosphorus accumulating organism (PAO) and microbial community structure in the AO-SBR system. The optimal treatment effect was achieved under the conditions of pH 7, DO 3.0 mg/L and particle dosage of 2.6 g Fe-C/g MLSS, and the removal rates of COD, TP, NH4 +-N and TN reached 80.56%, 91.46%, 69.42% and 57.57%. The proportion of phosphorus accumulating organisms (PAOs) increased from 4.54% in the SBR system to 10.89% in the ICME-SBR system at 10°C. Additionally, the metabolic rate of PAOs was promoted, and the activities of DHA and ETS both reached the maximum value of 13.34 and 102.88 μg·mg−1VSS·h−1. These results suggest that the ICME particles could improve the performance of activated sludge under low-temperature conditions. This technology provides a new way for upgrading the performance of sewage treatment in the cold area.

Performance of aerobic sequential batch reactor in the treatment of textile wastewaters

Performance of aerobic sequential batch reactor in the treatment of textile wastewaters

Removals of atenolol, gliclazide and prazosin using sequencing batch reactor

Emergence of organic micropollutants, specifically pharmaceutical compounds (PhCs) in receiving water bodies possess a great threat towards our ecosystem presently and in future. By that, evaluating and monitoring the removal of PhCs, specifically those highly consumed in a certain area, is considerably critical in attempt to minimize discharge of PhCs in our waters. Therefore, this study assessed the removal mechanisms of three highly consumed PhCs in Malaysia, namely atenolol, gliclazide and prazosin, by considering the hydrolysis, adsorption and biodegradation mechanisms of the selected compounds. Moreover, the removal of these compounds was demonstrated in an aerobic sequencing batch reactor (SBR) system treating actual domestic wastewater added with the selected compounds. The detection of PhCs was conducted using using Ultra-High Performance Liquid Chromatography Quadrupole-Time-Of-Flight Mass Spectrometry (UHPLC/QTOF-MS), followed by investigation of microbial community in the sludge sample by next generation sequencing (NGS). The results highlighted that atenolol was highly biodegradable with 83% efficiency in SBR system. Meanwhile, both gliclazide and prazosin show moderate biodegradation efficiency at 41%. The results also demonstrated that gliclazide and prazosin exhibited recalcitrant behavior towards the biological treatment. In addition, prazosin was presumed to be hydrolyzed and exist as different chemical structure in the aqueous phase during treatment process. The microbial community analysis revealed Mycobacterium as one of the potential microbes in biodegradation of PhCs.

Effect of Carbon Source on Biological Nutrient Removal in an Anaerobic, Hypoxic, Anoxic, or Aerobic Sequencing Batch Reactor

AbstractA sequencing batch reactor was constructed to realize simultaneous nitrification and denitrification (SND) and denitrifying phosphorus removal (DPR). The influence of different carbon sourc...

Enhancing biological nitrogen and phosphorus removal performance in aerobic granular sludge sequencing batch reactors by activated carbon particles

Long start-up periods for aerobic granular sludge (AGS) formation and establishment of P removal pathways are challenges for widespread implementation of AGS process. External additives such as activated carbon (AC) attracted interest for accelerating AGS formation. However, the roles of AC in granulation and biological nutrient removal (BNR) are not understood. Here, the role of AC was investigated in decreasing start-up periods in AGS formation and BNR under different carbon substrate conditions (i.e., acetate (HAc), propionate (HPr) and HAc-HPr) in sequencing batch reactors (SBRs). AC addition increased aggregation index and settleability of activated sludge (AS) inoculum which minimized AS washout from SBRs. AC addition hastened AGS formation and establishment of BNR pathways by facilitating AS retention and biofilm formation. Feeding HAc or HAc-HPr supported better granulation (MLSS: 6–7 g l−1, SVI: 30–40 ml g−1) than HPr (MLSS: 4 g l−1, SVI: 70). The start-up periods for efficient total nitrogen (TN) removals were decreased to 22 and 16 d from 38 to 25 d, respectively, in AC augmented SBRs fed with either HAc or HAc-HPr. TN removals were higher at ≥95% in HAc or HAc-HPr fed SBRs. Total phosphorus (TP) removals were also higher in AC-augmented SBRs at 80% and ≥90% in HAc and HAc-HPr fed SBRs, respectively. In contrast, TN and TP removals were lower at 70% and 35%, respectively, in HPr fed SBR. Ammonium was primarily removed via nitritation-denitritation pathway. Phosphorus removal was at 1.7 to 2-fold higher in AC augmented SBRs and driven by enhanced biological phosphorus removal (EBPR) pathway. MiSeq sequencing and qPCR revealed higher enrichment of polyphosphate accumulating organisms (PAOs), denitrifying PAOs, and ammonia oxidizers in AC-augmented SBRs fed with HAc or HAc-HPr. This study demonstrates that AC addition can be considered for enrichment of PAOs and establishment of EBPR in aerobic granular SBRs.

Aerobic sequential batch reactor for domestic sewage treatment: parametric optimization and kinetics studies

Abstract Domestic sewage (DS) was first treated in aerobic sequential batch reactor (SBR). In order to increase the treated water quality, DS from SBR was further treated using electrocoagulation (EC) and Ion exchange (IE) process. In the SBR study, process parameters such as hydraulic retention time (HRT) and reactor fill time (t f ) was optimized at various volume exchange ratio (VER) of 0.534, 0.4, 0.266, and 0.133. The best HRT and t f were observed to be 0.78 day (d) and 2 h, respectively, providing 72.37% chemical oxygen demand (COD) reduction (initial value of COD = 270 mg/dm3). Kinetics of biodegradation in SBR was also studied. The second stage treatment was performed in EC reactor at 1 ampere (A) current for 30 min electrolysis time (t R). EC reactor, further reduced COD and biological oxygen demand (BOD) up to 72 and 21 mg/dm3 from its average initial COD and BOD of 94 and 23 mg/dm3, respectively. Second stage treatment in IE process reduced hardness, sulphate, and phosphate up to 15, 0.05, and 0.13 mg/dm3 from its initial value 350, 5.48 and 1.16 mg/dm3, respectively. The treated water can be used as potable water after disinfection as its water quality is near to river water.

Formaldehyde biodegradation in an ASBR-SBR system: an effective treatment solution for furniture industry painting booth wastewater

Formaldehyde (HCHO) is a toxic organic compound with carcinogenic properties which is present in the furniture industry painting booth wastewater (PBW) and does not receive adequate treatment in its industrial environment. This effluent treatment commonly occurs by physicochemical processes that do not remove formaldehyde, while advanced treatment methods are costly for industrial scale application. This study assessed a system consisting of an anaerobic sequential batch reactor (ASBR) followed by an aerobic sequential batch reactor (SBR) for the PBW treatment. The system performance was evaluated by the gradual increase of HCHO concentration from 34 ± 5 to 232 ± 10 mg HCHO L−1, and chemical oxygen demand (COD) from 585 ± 8.4 to 3960 ± 100 mg O2 L−1, performed with cycle time of 4 days in ASBR and 2 days in SBR, evaluating the formaldehyde potential toxicity on anaerobic biomass. The ASBR-SBR system removed 99% of COD and HCHO until initial concentration of 180 ± 7 mg HCHO L−1. The HCHO concentration increase to 232 ± 10 mg L−1 reduced the removal efficiency of organic matter to 72% in ASBR due to partial inhibition of microorganisms caused by formaldehyde toxicity. However, under these conditions, the SBR was efficient and removed the remaining organic matter by 98%. The performance of ASBR-SBR showed that this simple system was suitable for the PBW treatment at the evaluated concentrations.