Upflow Anaerobic Sludge Blanket Reactor Research Articles

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.

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.

Preliminary Study of Up-Flow Anaerobic Sludge Blanket (UASB) Technology for Energy Recovery from Domestic Wastewater

New efforts are increasingly oriented towards the search for sustainable Waste Water Treatment Plant (WWTP) designs. The use of anaerobic digestion processes allows energy production during the treatment of wastewater. However, this technology has been poorly implemented for domestic wastewater due its low organic matter content. In this work, the generation of biogas from municipal wastewater has been studied through anaerobic digestion treatment. UASB effluent has been fed to a membrane photobioreactor (MPBR) where developed indigenous microalgae-bacteria consortia contributes to organic matter and nutrients recovery from digested wastewater and membrane allows continuous regenerated wastewater production as permeate stream. The study was performed at pilot scale making use of an Y configuration UASB, operated under psychrophilic conditions. In addition, the energy production potential of different valorisable substrates, which are residual streams from different treatment processes, was studied at lab scale: concentrate from direct ultrafiltration (DUF) membrane and sludge from conventional membrane bioreactors (MBR), in order to define the potentiality of technological trains with UASB reactors. Anaerobic digestion yields interesting results that should be considered, such as the fact that energy recovery in MBR is lower than that achieved in DUF, where a higher concentration of organic matter is obtained, and therefore, a greater energy obtainment is achieved.

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.

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.

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.

Improving the quality of produced water discharged in open waters by incorporating a microbiological treatment on operating offshore platforms

Produced water is the water that comes along with oil during the reservoir extraction and is the main subproduct of the petroleum industry, accounting for 3 to 5 times the global production of oil. The produced water separated from the oil still contains some oily fractions in its composition, making it necessary for some treatment before its discard (most common practice adopted on offshore platforms) or reuse. The traditional method of treatment is based on the physical separation of oil and water, driven by their density difference. This type of treatment is unable to remove dissolved or small diameter particles dispersed, which turned out to be an issue in face of some new legislation worldwide that lowered the maximum amount of total oil and grease (TOG) the water can have for its discharge. Biological treatment is a widespread method for treating wastewater in several different industries due to its relative simplicity and low operational costs. Nevertheless, as it is a treatment that normally requires large-volume vessels, it is not used on offshore platforms due to a lack of space for such high dimension equipment. The objective of this research was to carry out a literature review using the article and patent search bases to find technical options that allow the use of biological treatment for water produced on offshore oil production platforms. Next, propose a model to incorporate biological treatment and estimate the performance of this produced water treatment model. An arrangement was proposed to convert a cargo tank of an operating offshore oil platform into a microbiological reactor. The conversion could be useful to treat the produced water that has a concentration of oil above the maximum limit allowed to discharge or to promote the additional extraction of a fraction of oil that could not be removed by the conventional treatment plants. The objective of this research was to perform a literature review to find technical options that could allow the use of biological treatment for the produced water in offshore oil-producing platforms, to propose a model to incorporate the biological treatment, and to estimate the performance of this model treating produced water. After researching articles and patents in the literature, it was seen that the Upflow Anaerobic Sludge Blanket (UASB) was the best type of reactor to be incorporated into an offshore platform. The reactor was chosen since it had good performance in treating produced water anaerobically and low sludge production. The UASB reactor most resembled the arrangement of a cargo tank, which was a paramount factor for the feasibility of the process's success. It is expected that the cargo tank converted to an UASB could remove at least an extra 30% of the total oil and grease (TOG) when compared to the traditional physical removal process existent for the produced water. However, it is still necessary to perform some laboratory tests to better predict the removal rate that would be observed in using this microbiological treatment with the high salinity-produced water from pre-salt Brazilian fields.

Physiological suitability of sulfate-reducing granules for the development of bioconcrete.

Regular monitoring and timely repair of concrete cracks are required to minimize further deterioration. Self-healing of cracks has been proposed as an alternative to the crack maintenance procedures. One of the proposed techniques is to use axenic cultures to exploit microbial-induced calcite precipitation (MICP). However, such healing agents are not cost-effective for in situ use. As the market for bio-based self-healing concrete necessitates a low-cost bio-agent, nonaxenic sulfate reducing bacterial (SRB) granules were investigated in this study through cultivation in an upflow anaerobic sludge blanket reactor. The compact granules can protect the bacteria from adverse conditions without encapsulation. This study investigated the microbial activities of SRB granules at different temperatures, pH, and chemical oxygen demand concentrations which the microbes would experience during the concrete casting and curing process. The attenuation and recovery of microbial activities were measured before and after the exposure. Moreover, the MICP yield was also tested for a possible use in self-healing bioconcrete. The results consistently showed that SRB granules were able to survive starvation, high temperature (50-60°C), and high pH (12), together with scanning electron microscope/energy dispersive spectrometry/X-ray diffraction analysis evidence. Microbial staining analysis demonstrated the formation of spores in the granules during their exposure to harsh conditions. SRB granule was thus demonstrated to be a viable self-healing nonaxenic agent for low-cost bioconcrete.

Microbial dynamics and methanogenic potential of co-digestion of sugarcane vinasse and dairy secondary effluent in an upflow anaerobic sludge blanket reactor

Co-digestion is a strategy that may prevent microbial inhibition during the anaerobic treatment of sugarcane vinasse, a substrate with highly biodegradable organic load, acidity, and toxic compound levels (e.g., sulfates, phenols). In this context, this study evaluated the microbial dynamics and methanogenic potential throughout the co-digestion of sugarcane vinasse and secondary effluent from the dairy industry in a mesophilic lab-scale upflow anaerobic sludge blanket (UASB) reactor. Periodic next-generation sequencing (NGS) analyses revealed an increase in the relative abundance of the phylum Euryarchaeota (+8.6 % after inoculation), predominating hydrogenotrophic methanogens (Methanobacterium and Methanobrevibacter) at the end of the operation. Moreover, the average methane yield was 221 mLCH4 gCODrem-1, with 69 % of organic matter removal. These results evidenced a progressive acclimation of the anaerobic microbial community to the substrate and a stable operation. Therefore, the proposed experiment demonstrates energy advantages for the agro-industrial sector by implementing a similar but full-scale treatment plant.

Performance evaluation of a novel upflow anaerobic sludge blanket reactor with built-in downflow hanging sponge module for the treatment of municipal sewage.

The present study investigates the potential of a novel upflow anaerobic sludge blanket (UASB) reactor with a built-in polishing facility for the treatment of municipal sewage. A laboratory-scale reactor, which combined an inner-centric hybrid UASB module and an outer concentric downflow hanging sponge (DHS) unit, was designed and fabricated as a part of this research work. The reactor had been continuously operated for 210 days under ambient conditions. With anaerobically digested sewage sludge (seed sludge blended with Locust bean gum polymer) as inoculum, the reactor attained a successful startup in 40 days. Ensuring startup, the reactor was employed under varying organic loading rates (OLR) from 0.87 to 5.09 kg COD/m3/d, with corresponding hydraulic retention times (HRT) of 24-4 h. The novel UASB reactor made its mark with a high COD and TSS removal of 93.2% and 93%, respectively, under the optimum conditions of 6-h HRT. In addition, biogas rich in methane content (68%), with a maximum specific yield of 0.42± 0.02 m3 biogas /kg COD destroyed, was generated. The VSS/TSS ratio observed a steady rise (0.51 to 0.75) with increasing sludge age, bearing witness to the active growth of biomass. Hence, in brief, the novel UASB reactor can be coined as an energy economic system with improved effluent quality.

Electrical voltage application as a novel approach for facilitating methanogenic granulation

Despite having high-rate methanogenic performance, up-flow anaerobic sludge blanket reactor still has challenges regarding long-start up period (3–8 months) for granulation. In this study, “electrical voltage (EV, 0.3 V) application” was attempted for facilitating granulation in the continuous operation with increased organic loading rates (0.5–11.0 kg COD/m3/d). Up to 11.0 kg COD/m3/d, EV-reactor exhibited the stable performance, while the control failed. After 49 days of operation (at 7 kg COD/m3/d), the granules collected from EV-reactor had larger diameter (2.3 vs 1.6 mm), higher settling velocity (2.6 vs 1.9 cm/s), and higher hydrophobicity (52.1 % vs 34.5 %), compared to the control. EV application also increased the specific methanogenic activity for propionate and hydrogen almost by two times. The relative abundance of Pseudomonas sp. (quorum sensing (QS)-related microbe) in EV-reactor was 17 % higher than that in the control. In addition, EV application increased the expression of QS genes significantly by 27 times.

A comparative study for hybrid UASB reactor performance using polyethylene media and luffa sponge as biofilm support.

This paper study the performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor treating low-strength synthetic wastewater using different biofilm supporting materials. Two identical reactors are constructed and operated at constant up-flow velocity of 0.1m/hr., inflow rate of 9.76L/d, and hydraulic retention time (HRT) of 8.26hours. The Start-up phase, using seed sludge for existing wastewater treatment plant, lasted until the efficiency of chemical oxygen demand (COD) removal of both reactors reached 80%. Polyethylene (PE) media are added to one of the reactors and luffa sponge is used in the second reactor. Results show increased COD removal efficiency up to about 90% at 20°C and biogas production rates from 3.8*10-3 till 7.5*10-3m3 CH4/kg CODr using PE media. The COD removal efficiency reaches about 95% at 20°C using luffa sponge and biogas production rates up to 6.5*10 -3m3 CH4/kg CODr are achieved before clogging problem is observed. Effect of HRT reduction, from 8.26 to 4.13hours, on removing clogging is investigated. Reduction in COD removal efficiencies is observed at low ambient temperatures during seasonal variations of 15-25°C. AFM and SEM analysis are used to examine sludge granulation and biofilm formation.