Upflow Anaerobic Sludge Blanket Research Articles

Bioenergy recovery potential from upflow microaerobic sludge blanket reactor fed with swine wastewater

This paper reports the bioenergy recovery potential inherent to swine wastewater (SWW) when treated in an upflow microaerobic sludge blanket reactor (UMSB) operating with different oxygen loads. The UMSB reactor performance was compared with the one achieved with an upflow anaerobic sludge blanket (UASB) reactor that worked as a control. The biogas production was measured on a lab scale and used to estimate the UMSB reactor self-sufficiency energy. The highest methane yield achieved in the UMSB reactor was 228.6 NL kgCOD−1 d−1 at an organic loading rate (OLR) of 12.2 kgCOD m−3d−1 (HRT of 10 h). Both OLR and air dose increase generated methane dilution in the biogas, which reduced the possibility of electrical energy recovery. Nevertheless, the results showed that the UMSB reactor was self-sufficient and had energy efficiency at the 12 h HRT with doses of 0.17 and 0.25 LO2 Lfeed−1d−1 and at the 10 h HRT with a dose of 0.25 LO2 Lfeed−1d−1. The UMSB reactor achieved an energy return on investment (EROI) of 11.6–18.7, showing a potentially viable alternative for power generation.

Characterization and evaluation of the life cycle of energy use from drying bed sludge

This study sought to characterize sludge digested in Upflow Anaerobic Sludge Blanket (UASB) reactors during the drainage process of Drying Bed Sludge (DBS) to conduct a Life Cycle Assessment (LCA) for different DBS disposal scenarios. In addition, the potential recovered energy from the waste material was verified when submitted to Anaerobic Digestion (AD) or when combusted through simulation software SimaPro®. Laboratory analyses were conducted with the collected samples from a wastewater treatment plant in Itajubá, Minas Gerais, Brazil. The calorific value, ashes generated from the burning process, and methane production were conducted in two experiments for a qualitative and quantitative evaluation of the biogas generated. The scenarios included DBS disposal in landfills and ditches, DBS biodigestion, and combustion. The methane yield generated by DBS resulted in a lower value compared to DBS produced by the UASB reactor disposal system. The LCA results show that the impact category pertaining to global warming is indeed influenced for all scenarios, almost entirely comprised of biogas emissions coming from the drying bed waste. Heavy metal emissions may occur during combustion, which may impact human toxicity. Under the scenario in which DBS undergoes biodigestion, the pollutants include nitrogen oxide, sulfur monoxide, and carbon monoxide.

Spatial distributions of granular activated carbon in up-flow anaerobic sludge blanket reactors influence methane production treating low and high solid-content wastewater

The impacts of granular activated carbon (GAC) spatial distributions in up-flow anaerobic sludge blanket (UASB) reactors treating different solid-content wastewater were evaluated in the present study. When treating high solid-content wastewater, the highest methane yield was observed for UASB supplemented with self-floating GAC (74.2 ± 3.7 %), which was followed by settled + self-floating GAC reactor (65.1 ± 3.8 %), then settled GAC reactor (58.3 ± 1.4 %). When treating low solid-content wastewater, all UASBs achieved improved methane yield, and settled + self-floating GAC reactor achieved the highest methane yield (83.4 ± 3.3 %). Self-floating GAC amended reactor showed the best performance for treating high solid-content wastewater, while settled + self-floating GAC amended reactor was optimal for treating medium and low solid-content wastewater. The spatial distributions of microbial communities differed in the reactors with settled GAC and floating GAC. This study underlines the importance of considering feedwater characteristics when adopting GAC-based UASB processes.

Two-stage anaerobic membrane bioreactor for co-treatment of food waste and kitchen wastewater for biogas production and nutrients recovery

Co-digestion of organic waste and wastewater is receiving increased attention as a plausible waste management approach toward energy recovery. However, traditional anaerobic processes for co-digestion are particularly susceptible to severe organic loading rates (OLRs) under long-term treatment. To enhance technological feasibility, this work presented a two-stage Anaerobic Membrane Bioreactor (2 S-AnMBR) composed of a hydrolysis reactor (HR) followed by an anaerobic membrane bioreactor (AnMBR) for long-term co-digestion of food waste and kitchen wastewater. The OLRs were expanded from 4.5, 5.6, and 6.9 kg COD m−3 d−1 to optimize biogas yield, nitrogen recovery, and membrane fouling at ambient temperatures of 25–32 °C. Results showed that specific methane production of UASB was 249 ± 7 L CH4 kg−1 CODremoved at the OLR of 6.9 kg TCOD m−3 d−1. Total Chemical Oxygen Demand (TCOD) loss by hydrolysis was 21.6% of the input TCOD load at the hydraulic retention time (HRT) of 2 days. However, low total volatile fatty acid concentrations were found in the AnMBR, indicating that a sufficiently high hydrolysis efficiency could be accomplished with a short HRT. Furthermore, using AnMBR structure consisting of an Upflow Anaerobic Sludge Blanket Reactor (UASB) followed by a side-stream ultrafiltration membrane alleviated cake membrane fouling. The wasted digestate from the AnMBR comprised 42–47% Total Kjeldahl Nitrogen (TKN) and 57–68% total phosphorous loading, making it suitable for use in soil amendments or fertilizers. Finally, the predominance of fine particles (D10 = 0.8 μm) in the ultrafiltration membrane housing (UFMH) could lead to a faster increase in trans-membrane pressure during the filtration process.

Enhanced biological nitrogen and phosphorus removal from sewage driven by fermented glycerol: comparative assessment between sequencing batch- and continuously fed-structured fixed bed reactor.

The nutrient biological removal from sewage, especially from anaerobic reactor effluents, still represents a major challenge in conventional sewage treatment plants. In this work, the nitrogen and phosphorus removal from anaerobic pre-treated domestic sewage in an up-flow anaerobic sludge blanket (UASB) reactor was assessed in a structured fixed bed reactor (SFBR) operated in a continuous and in a batch mode using polyurethane foam as material support for biomass and fermented glycerol as the exogenous carbon source. The SFBR was operated as a sequencing batch reactor with cycles of 90, 120, and 150min under anaerobic, oxic, and anoxic conditions, respectively, reaching average efficiencies for total nitrogen and phosphorus removal of 88% and 56%, respectively. Fermented glycerol was added during the non-aerated periods. Under continuous feeding, the SFBR was operated with aeration/non-aeration periods of 2/1 (h) and 3/1 (h), hydraulic retention time of 12h, and a recirculation ratio of 3. Without fermented glycerol addition, the maximum removal of total nitrogen (TN) reached 42%, while adding glycerol in the non-aerated period improved TN removal to 64.9% (2/1h) and 69.5% (3/1h). During continuous operation, no phosphorus removal was observed, which was released during the non-aerated period, remaining in the effluent. Optical microscopy analyses confirmed the presence of polyphosphate granules and of the phosphorus accumulating organisms in the reactor biofilm. It was concluded that the batch feeding method was determinant for phosphorus removal. The structured fixed bed reactor with polyurethane foam proved to be feasible in the removal of organic matter and nutrients remaining in the UASB reactor effluent.

Hyper biohydrogen production from xylose and xylose-based hemicellulose biomass by the novel strain Clostridium sp. YD09

With increasing interest in biohydrogen as an alternative fuel to petroleum, it is essential to identify a hyper biohydrogen producer. In the present study, Clostridium sp. YD09 was isolated from a brewery wastewater upflow anaerobic sludge blanket digestion reactor; its 16S ribosomal RNA sequencing analysis showed 96 % similarity to Clostridium beijerinckii. Clostridium sp. YD09 produced the highest cumulative volume of hydrogen using xylose as the substrate (optimal concentration of 10 g/L) to obtain 1.21 mol H2/mol xylose. Furthermore, Clostridium sp. YD09 tolerates various inhibitors from pre-treated lignocellulosic biomass up to a 0.1 % concentration. A maximum yield of 1.62 mol H2/mol xylose and 1.98 mL H2/mL media with 38- to 48-fold increase was recorded in ligno-hemicellulose xylose treated with biochar and activated carbon. The newly isolated Clostridium sp. YD09 can therefore be used for efficient biohydrogen production from xylose-based substrates.

The selectivity of electron acceptors for the removal of caffeine, gliclazide, and prazosin in an up-flow anaerobic sludge blanket (UASB) reactor.

This study attempts to investigate the relationship between the dominance of reducing conditions and the biotransformation of pharmaceutical compounds, which has been scarcely reported in a continuous anaerobic treatment process. Previous batch experiments have discovered the possible implications of different reducing conditions on the biotransformation process, but have failed to reflect actual removal performance due to substrate limitations and other operational factors. Continuously operating reactors commonly receive wastewater stream containing a wide range of electron acceptors that diversify the growth of microorganisms in anaerobic treatment. The alteration of the dominance of reducing conditions in a continuous anaerobic reactor may result in the improvement of biotransformation performance compared to a single reducing condition in a substrate-limited batch experiment. The removal of psychostimulant caffeine (CAF), anti-diabetic drug gliclazide (GCZ), and anti-hypertensive drug prazosin (PRZ) were examined through the operation of an up-flow anaerobic sludge blanket (UASB) reactor under predominant methanogenic condition (Phase I) and simultaneous reducing conditions provided by a nitrate supplement (Phase II). The results revealed high biotransformation performance for all three compounds (73-> 99%) in both Phase I and Phase II experiments and fitted the pseudo-first-order model. The biotransformation rate of CAF and PRZ were relatively lower by 25% and 29%, while the GCZ rate improvement doubled in Phase II compared to Phase I. The outcome from 16s rRNA sequencing suggested that the biotransformation of the compounds may be driven by Firmicutes and Bacteroidota in both phases, and Burkhorderiales and sulfate-reducing bacteria species in Phase II. This study proved preferential of reducing conditions does not negatively affect the biotransformation performance of each pharmaceutical compound in a continuous anaerobic reactor, but they led to varying biotransformation rate, hence shifting the microbial diversity.

Anaerobic domestic wastewater treatment in a sequencing granular UASB bioreactor: Feasibility study of the temperature effect on the process performance

A laboratory-scale sequencing granular up-flow anaerobic sludge blanket (UASB) reactor was applied for the treatment of synthetic domestic wastewater at 15, 25 and 35 °C. The experiments were performed at different hydraulic retention times (gradually decreasing from a maximum of 22 h to a minimum of 9 h). Results at 25 and 35 °C showed similar COD removal efficiency and specific biogas production in the range of 84–94% and 0.14–0.27 m3/kgCODremoved, respectively. At 15 °C lower COD removal kinetics were observed, and a minimum hydraulic retention time of 14 h was necessary to obtain an effluent in accordance with current Italian legislation. At all temperatures, high quality effluent was achieved in terms of total suspended solids (TSS) concentration, while nitrogen and phosphorus exceeded the Italian law limits, as they are not removed during the anaerobic digestion process. Moreover, dissolved methane in the liquid phase was analysed: methane lost with the effluents was on average ≈ 37% at 25 °C and ≈ 24% at 35 °C of the produced amount, thus revealing higher losses at lower temperatures for the increase of gas solubility. These results show the need of research on technologies aimed at removing or recovering such energetic greenhouse gas. However, effective biogas production and potentialities for nutrients’ recovery demonstrated in this study confirm the feasibility of the anaerobic process as sustainable treatment of low-strength wastewaters.

Long-term comparison of pilot UASB and AnMBR systems treating domestic sewage at ambient temperatures

The upflow anaerobic sludge blanket (UASB) reactor and the anaerobic membrane bioreactor (AnMBR) are leading candidates for high-rate anaerobic treatment of domestic wastewater. The objective of this study was to perform a long-term comparison on the treatment of domestic sewage by the UASB and AnMBR systems at pilot scale at ambient temperature conditions and relate this to full-scale performance from a range of domestic strength UASB reactors. Analysis of overall operation indicated that the pilot reactor was more likely to be effective in removing solids (and less effective in soluble COD) than full-scale reactors, but that both had comparable performance ranges (i.e., from very effective, to very ineffective). Analyzing both UASB and AnMBR pilot plants treating the same wastewater, it can be concluded that both systems could achieve comparable performance (the UASB for very short periods), with COD removal efficiencies of more than 90%. However, the UASB could only achieve this performance for weeks at a time with good solids retention and long (>15 h) hydraulic retention time (HRT). This performance in general was not sustainable. For the UASB, the average COD removal at 15-h HRT was approximately 50%, with a significant reduction in performance as the hydraulic loading increased (which effectively reduced the HRT). Conversely, the AnMBR system produced exceptional COD removal at an HRT of 9 h. Considering this, the sustained volumetric methane production (per volume of reactor) was approximately 4 times that in the AnMBR than in the UASB system.

Improving CH4/O2 energy ratio of meat processing wastewater treatment systems through micro-sieving

ABSTRACT Micro-sieving is an effective way to prevent organic pollutants enter the main biological process and reduce aeration intensity and sludge production. However, few researchers quantified the effect of micro-sieving on meat processing wastewater treatment. The current study developed Excel-based models to compare the energy consumption and production of historical, conventional and innovative systems. Historical and conventional systems employ activated sludge (AS), nitrification, and denitrification as the main biological processes. Innovative systems are designed by using up-flow anaerobic sludge blanket (UASB) and partial nitrification/Anammox (PN/A) as the main treatment processes. Results show that the CH4/O2 energy ratios of the innovative treatment system are as high as 10 times of the historical and conventional systems. Therefore, innovative system can achieve electrical self-sufficiency. Micro-sieving reduces 5% of aeration demand. Furthermore, the impact of micro-sieving on the innovative treatment systemis assessed by cost-benefit analysis. System with micro-sieving has the shortest payback time of 2.1 years and reduces cost of the innovative treatment system. An excel-based model was developed to quantify the impact of micro-sieving on energy and cost of innovative treatment system, thereby providing a valuable reference for future sustainable engineering design of meat processing wastewater treatment.

Molecular transformations of dissolved organic matter during UV/O3-assisted membrane filtration of UASB-treated real textile wastewater

A ceramic membrane reactor (CMR) integrated with in-situ UV/O3 was assessed for post-treatment of the effluent out of an up-flow anaerobic sludge blanket (UASB) reactor treating real textile wastewater, focusing on the transformation of dissolved organic matter (DOM). Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) revealed the transformation of heteroatomic DOM containing S, N or both to simpler DOM containing mainly C, H, and O atoms. The decreased N contents in products (N/C = 0.0249) compared to precursors (N/C = 0.0311) and the higher O/C ratios in the N-containing products suggest the removal of R–NH2 groups accompanying DOM oxidation. While, S-containing compounds in the products had lower O/C and H/C ratios, suggesting a reduced state and the transformation of R–SO3 to R–S–R. H-abstraction and OH addition were identified as the primary oxidation mechanisms, thus enhancing the dominance of highly unsaturated and phenolic DOM in the effluent (70.3%) compared to the feed (56.6%). The double bond equivalent (DBE) was also increased by 26% in the effluent compared to the feed and by 33% in products compared to precursors. These findings help understand the DOM transformation in UV/O3-assisted ceramic membrane reactors and call for comprehensive toxicity analyses of effluents from the advanced oxidation processes.

Anaerobic Digested Wastewater CO2 Sequestration Using a Biophotocatalytic System with a Magnetized Photocatalyst (Fe-TiO2)

This study presents a biophotocatalytic system as a sustainable technology for the recovery of clean water and renewable energy from wastewater, thereby providing a unique opportunity to drive industrialization and global sustainable development throughputs. Herein, inhouse magnetized photocatalyst (Fe-TiO2) with surface area 62.73 m2/g synthesized via co-precipitation, was hypothesized to hasten an up-flow anaerobic sludge blanket (UASB) reactor for the treatment of local South Africa municipality wastewater with the benefit of high-quality biogas production. A lab scale UASB process with a working volume of 5 L coupled with two UV-lights (T8 blacklight-blue tube, 365 nm, 18 W) was operated batchwise under mesophilic conditions for the period of 30 days with a constant organic load charge of 2.76 kg COD/m3. d. This biophotocatalytic system performance was investigated and compared with and without the Fe-TiO2 charge (2–6 g) with respect to effluent quality, biogas production and CO2 methanation. Using chemical oxygen demand (COD) measured as the degree of degradation of the pollutants, the best efficiency of 93% COD removal was achieved by a 4 g Fe-TiO2 charge at 14 days and pH of 7.13, as compared to zero charge where only 49.6% degradation was achieved. Under the same charge, cumulative biogas and methane content of 1500 mL/g COD.d and 85% were respectively attained as compared with the control with 400 mL/g COD.d and 65% methane content. Also, the energy produced can be used to offset the energy utilized by the UV-light for the wastewater abatement and other limitations of photocatalysis. The BP system was found to be an eco-friendly and cost-effective technology to be explored in water treatment settings.

Effects of sulfate concentration on anaerobic treatment of wastewater containing monoethanolamine using an up-flow anaerobic sludge blanket reactor

Monoethanolamine (MEA), a toxic organic chemical, is widely used in industries and is found in their wastewater. Anaerobic MEA degradation is an appropriate strategy to reduce energy and cost for treatment. Industry wastewaters also contain sulfate, but information on the effects of sulfate on MEA degradation is limited. Here, an up-flow anaerobic sludge blanket (UASB) for MEA-containing wastewater treatment was operated under psychrophilic conditions (18–20 ºC) to investigate the effects of sulfate on the microbial characteristics of the retained sludge. To acclimatize the sludge, the proportion of MEA in the influent (containing sucrose, acetate, and propionate) was increased from 15% to 100% of total COD (1500 mg L–1); sulfate was then added to the influent. The COD removal efficiency remained above 95% despite the increase in MEA and sulfate. However, granular sludge disintegration was observed when sulfate was increased from 20 to 330 mg L–1. Batch tests revealed that propionate and acetate were produced as the metabolites of MEA degradation. In response to sulfate acclimation, methane-producing activities for propionate and hydrogen declined, while sulfate-reducing activities for MEA, propionate, and hydrogen increased. Accordingly, acclimation and changes in dominant microbial groups promoted the acetogenic reaction of propionate by sulfate reduction.

Pollutant Removal and Energy Recovery from Swine Wastewater Using Anaerobic Membrane Bioreactor: A Comparative Study with Up-Flow Anaerobic Sludge Blanket

Due to its high content of organics and nutrients, swine wastewater has become one of the main environment pollution sources. Exploring high-efficient technologies for swine wastewater treatment is urgent and becoming a hot topic in the recent years. The present study introduces anaerobic membrane bioreactor (AnMBR) for efficient treatment of swine wastewater, compared with up-flow anaerobic sludge blanket (UASB) as a traditional system. Pollutant removal performance, methanogenic properties, and microbial community structures were investigated in both reactors. Results showed that by intercepting particulate organics, AnMBR achieved stable and much higher chemical oxygen demand (COD) removal rate (approximately 90%) than UASB (around 60%). Due to higher methanogenic activity of anaerobic sludge, methane yield of AnMBR (0.23 L/g-COD) was higher than that of UASB. Microbial community structure analysis showed enrichment of functional bacteria that can remove refractory organic matter in the AnMBR, which promoted the organics conversion processes. In addition, obvious accumulation of acetotrophic and hydrotrophic methanogens in AnMBR system was recorded, which could broaden the organic matter degradation pathways and the methanogenesis processes, ensuring a higher methane yield. Through energy balance analysis, results concluded that the net energy recovery efficiency of AnMBR was higher than that of UASB system, indicating that applying AnMBR for livestock wastewater treatment could not only efficiently remove pollutants, but also significantly enhance the energy recovery.

The Aggregation and Dissolution of Citrate-Coated AgNPs in High Ammonia Nitrogen Wastewater and Sludge from UASB-Anammox Reactor.

Silver nanoparticles (AgNPs) are released into the sewage pipes and ultimately wastewater treatment plants during manufacturing, use, and end–life disposal. AgNPs in wastewater treatment plants aggregate or dissolve, and may affect the microbial community and subsequent pollutant removal efficiency. This study aims to quantitatively investigate the fate of AgNPs in synthetic high ammonia nitrogen wastewater (SW) and sludge from an up–flow anaerobic sludge blanket (UASB) anammox reactor using a nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic absorption spectroscopy (AAS). Results showed that 18.1 mM NH4+, 2.11 mM Mg2+ in SW caused less negative zeta potential (ζ−potential, −18.4 vs. −37.4 mV), aggregation (388.8 vs. 21.5 nm), and settlement (80%) of citrate−coated AgNPs (cit−AgNPs) in 220 min. The presence of 18.5 mM Cl− in SW formed AgCl2−, AgCl(aq) and eventually promoted the dissolution (9.3%) of cit−AgNPs. Further exposure of SW−diluted AgNPs to sludge (42 mg L−1 humic acid) and induced a more negative ζ−potential (−22.2 vs. −18.4 mV) and smaller aggregates (313.4 vs. 388.8 nm) due to the steric and hindrance effect. The promoted Ag dissolution (34.4% vs. 9.3%) was also observed after the addition of sludge and the possible reason may be the production of Ag(NH3)2+ by the coexistence of HA from sludge and NH4+ from SW. These findings on the fate of AgNPs can be used to explain why AgNPs had limited effects on the sludge−retained bacteria which are responsible for the anammox process.

Effects of operational variations of micro-oxygenation and pH shock on the competition between methane production and sulfate reduction in a UASB reactor

To investigate the effect of oxygen, pH shock, and H2S inhibition on the competition between sulfate-reducing bacteria (SRB) and methane-producing archaea (MPA), a UASB reactor treating wastewater containing sulfate, ethanol and acetate was operated for 360 days. With micro-oxygenation performed at a flow rate of 100 mL/min in the upper part of the up-flow anaerobic sludge blanket (UASB) reactor, the sulfate removal and total sulfide concentration increased to 68.6% and 500 mg S/L, while the methane production rate slightly reduced from 2.5 to 2.1 L/L/d. However, methane production was still the main reaction in the reactor. The pH shock and high H2S concentration finally changed the competition results between SRB and MPA. Sulfate reduction was not affected while methane production was completely inhibited at H2S concentration more than 200 mg/L. Complete sulfate reduction (99.0%) was maintained over the long term with a stable organic COD removal (70.4%). The experimental results proved that in the complete sulfate-reducing stage, ethanol was mainly utilized by incomplete-oxidizing SRB for sulfate reduction.

Performance of UASB reactor treating waste activated sludge: Effect of electro-chemical disintegration on the anaerobic microbial population structure and abundance

The electro-Fenton (EF) disintegration using iron electrodes was performed for the pretreatment of waste activated sludge (WAS). The effect of this electro-chemical pretreatment on anaerobic digestion (AD) performance and microbial population structure was studied. An improvement of biodegradability and bioaccessibility of organic matter was demonstrated. AD of pretreated WAS in an up-flow anaerobic sludge blanket reactor (UASB) resulted to an increase of biogas production by 60 % compared to control reactor without disintegration. PCR-DGGE and real-time qPCR analyses showed that the high abundance of bacteria and the coexistence of Coprothermobacter in the UASB digestate fed with disintegrated sample established a stable bacterial association which is in line with the AD performance. Besides, the increased number of methanogens along the process allowed the improvement of methane production in comparison to control reactor.

Performance evaluation of a full-scale upflow anaerobic sludge blanket reactor coupled with trickling filters for municipal wastewater treatment in a developing country

Poor wastewater management remains a critical health and environmental challenge in most developing countries in Sub-Saharan Africa due to the lack of adequate infrastructure for collection and treatment. This study evaluated the performance and methane production of a full-scale upflow anaerobic sludge blanket (UASB) reactor of capacity 18000 m3/d, with post-treatment unit: trickling filters followed by final settling tanks for municipal wastewater treatment in Ghana. Data was collected on operational conditions and physicochemical parameters of wastewater (influent and effluent) over a period of 35 weeks in 2021 (from January to August). The influent biochemical oxygen demand to chemical oxygen demand (BOD:COD) ratio was 0.58 ± 0.16, indicating the presence of highly biodegradable compounds in the sewage. Operational conditions for the UASB reactors were observed to be within the optimal range for anaerobic systems, with an applied organic loading rate of 1.30 ± 0.79 kgCOD/m3/d. Generally, Plant performance was satisfactory with carbon removal at 93% for COD and 98% for BOD. Biogas yield was 0.2 m3/kgCOD removed, culminating in an average biogas production rate of 831.6 ± 292.7 m3/d. Average methane composition was 64.7 ± 11.9% of the biogas output, whilst an estimated 35% of the methane generated remained dissolved in the UASB effluent. The UASB reactor presents an efficient technology that can be implemented in developing countries for effective and sustainable wastewater management.

Enhanced biogas production and substrate degradation through the intermittent operation of modified upflow anaerobic sludge blanket-static granular bed reactor series.

In the present study, the performance of a modified upflow anaerobic sludge blanket (MUASB) reactor-static granular bed reactor (SGBR) series in intermittent operation was analyzed for the treatment of synthetic wastewater. The reactor series was operated with a hydraulic retention time (HRT) of 24 h. The maximum chemical oxygen demand (COD) removal and biogas production of the reactor series obtained during the intermittent operation were 99 ± 0.29% and 0.529 ± 0.03 m3 /kg CODdigested , respectively. One-way analysis of variance (ANOVA) indicated a significant difference in biogas production during continuous and intermittent operations, whereas the COD removal was similar. Intermittent operation of the reactor series yielded a 56.05% increase in biogas production when compared with the continuous operation. The reactor series was maintained stable throughout the operational period. The maximum total suspended solids (TSS) removal and total nitrogen (TN) removal of the reactor series during the intermittent operation were 91.67% and 72.37%, respectively. Intermittent operation of the reactor series can be considered advantageous because of the reduced operational cost and enhanced biogas production in addition to COD removal. PRACTITIONER POINTS: Intermittent operation of MUASB-SGBR series in terms of COD removal is evaluated. COD removal of reactor series was similar in intermittent and continuous operation. Biogas production in intermittent operation was superior to continuous operation. Reactor series performance is also compared with continuous operation using one-way ANOVA.

Impact of varying hydraulic retention time for treating distillery effluent in activated sludge system to combat the environmental and health hazards

Ethanol-distilleries are the key supporter to the world's economy, but these are moreover one of the major sources of environmental pollution that can impact the human heath if the effluents are not treated in proper manners. Distillery effluents with high biological oxygen demand (BOD) and chemical oxygen demand (COD) contains toxic chemicals which are reported to be of carcinogenic and mutagenic in nature. One of the widely used technology for the distillery wastewater treatment is based on up-flow anaerobic sludge blanket (UASB) technology along with activated sludge process. This technology has fulfilled a need for high efficiency treatment of wastes from various distilleries. With the increasing demands of distillery units and strict guidelines by government agencies for the environment protection, more efforts are required to achieve the zero liquid discharge (ZLD). The research reported in this paper is an effort to perform the in-situ study for evaluating the impact of varying retention times on the efficiency of the condensate Polishing Unit (CPU) based on UASB technology along with activated sludge process for ZLD. The primary objective was to determine pH, BOD and COD after increasing the HRTs in the aeration tank.