Anaerobic granular sludge treatment processes have been continuously developed, although the anaerobic sludge granulation process was not clearly understood. In this review, an upflow anaerobic ...sludge blanket (UASB), an expanded granule sludge blanket (EGSB), and a static granular bed reactor (SGBR) were introduced as components of a representative anaerobic granular sludge treatment processes. The characteristics and application trends of each reactor were presented. The UASB reactor was developed in the late 1970s and its use has been rapidly widespread due to the excellent performance. With the active granules, this reactor is able to treat various high-strength wastewaters as well as municipal wastewater. Most soluble industrial wastewaters can be efficiently applied using a UASB. The EGSB reactor was developed owing to give more chance to contact between wastewater and the granules. Dispersed sludge is separated from mature granules using the rapid upward velocity in this reactor. The EGSB reactor shows the excellent performance in treating low-strength and/or high-strength wastewater, especially under low temperatures. The SGBR, developed at Iowa State University, is one of anaerobic granular sludge treatment processes. Although the configuration of the SGBR is very simple, the performance of this system is similar to that of the UASB or EGSB reactor. The anaerobic sludge granulation processes showed excellent performance for various wastewaters at a broad range of organic loading rate in lab-, pilot-scale tests. This leads to erect thousands of full-scale granular processes, which has been widely operated around the world.
•Anaerobic sludge granulation is a key parameter for maintaining granular processes.•Anaerobic granular digestion processes are applicable for various wastewaters.•The UASB is an economic high-rate anaerobic granular process.•The EGSB can treat high-strength wastewater using expanding granules.•The SGBR is applicable for mid to low strength wastewater.
•Diatomite and maifanite were novel used in UASB reactors.•The support materials accelerated anaerobic sludge granulation.•Favorable bacterial community formed in reactors with diatomite and ...maifanite.•Support materials improved UASB performance when treating refractory wastewater.
Novel diatomite (R1) and maifanite (R2) were utilized as support materials in an up-flow anaerobic sludge bed (UASB) reactor for the treatment of recalcitrant petroleum wastewater. At high organic loadings (11kg-COD/m3·d), these materials were efficient at reducing COD (92.7% and 93.0%) in comparison with controls (R0) (88.4%). Higher percentages of large granular sludge (0.6mm or larger) were observed for R1 (30.3%) and R2 (24.6%) compared with controls (22.6%). The larger portion of granular sludge provided a favorable habitat that resulted in greater microorganism diversity. Increased filamentous bacterial communities are believed to have promoted granular sludge formation promoting a conductive environment for stimulation methanogenic Archaea. These communities had enhanced pH tolerance and produced more methane. This study illustrates a new potential use of diatomite and maifanite as support materials in UASB reactors for increased efficiency when treating refractory wastewaters.
Display omitted
•A continuous-flow process of nitritation and ANAMMOX was used to treat leachate.•The mature landfill leachate without diluted by tap-water was used in this study.•Associated ...inhibition of FA and FNA to NOB facilitate realization of nitritation.•The conversion rate of NH4+-N and NAR in A/O were up to 95% and 92%, respectively.•Quantitative PCR analyzed the proportions of AOB, NOB and anammox in A/O and UASB.
Due to the difficulty in removing nitrogen from landfill leachate, a combined continuous-flow process of nitritation and anammox was applied to process mature leachate. The transformation rate of ammonia and nitrite accumulation ratio in A/O reactor were kept above 95% and 92% respectively through associated inhibition of free ammonia (FA) and free nitrous acid (FNA) to NOB. The total nitrogen volumetric load of anammox in an UASB reactor was brought up from 0.5kg/(m3·d) to 1.2kg/(m3·d) by gradually increasing influent substrate concentration and reducing hydraulic retention time (HRT). The results show that COD from mature leachate did not bring obvious inhibition effects to anammox. Under concentrations of influent ammonia and COD which were respectively 1330mg/L and 2250mg/L, the removal efficiencies of TN and COD reached 94% and 62% respectively. In the quantitative PCR reactions, the proportions occupied by AOB, NOB and anammox in A/O were 11.39%, 1.76% and 0.05% respectively; and proportions of those in UASB were 0.35%, 4.01% and 7.78% respectively.
This study aimed at evaluating the energy potential of the by-products (sludge and biogas) produced in full-scale UASB-based sewage treatment plant (STP). The work was developed at the Laboreaux STP ...(Population = 70,000 inhabitants), located in the city of Itabira, in the state of Minas Gerais – Brazil. To determine the biogas energy potential, the volumetric production and its composition were monitored. The dehydrated sludge from filter press was characterized according to immediate composition, elemental composition, lower calorific value (LCV) and higher calorific value (HCV). Overall, the gross energy potentials of the biogas and sludge produced in the STP were 7518 MJ d−1 and 10,962 MJ d−1, respectively. Considering the use of biogas to produce electricity (efficiency of 30%), it could be possible to supply 57.6% of energy demand of STP. With a thermal treatment of sludge from filter press, with or without energy recovery, it would have a reduction of mass disposal in the landfill in the order of 46.0% that represents a benefit in the sludge management.
•A mixture of municipal and piggery wastewater was used for microalgae cultivation.•Pre-treatment of wastewater mixture by UASB showed high efficiency (>90%).•Microalgae production and nutrient ...removal from wastewater mixture were reported.
Microalgae are a source of high-valuable products covering a wide range of applications. However, costs incurred by cultivating them make it an expensive process. The combination of wastewater treatment and microalgae cultivation is a viable option to reduce expenses related to cultivation. However, municipal wastewater from the centralized Brazilian sanitation system is highly diluted, and it is technically and economically impractical to use it for microalgae cultivation. As an alternative, diluted effluent can be mixed with a different kind of wastewater, aiming to increase the nutrient concentration (carbon, nitrogen and phosphorus) for microalgae cultivation. In this study, microalgae cultivation and wastewater mixture (municipal and piggery wastewater) treatment were monitored for four weeks. The pilot treatment system consisted of UASB as pre-treatment and Chlorella sorokiniana cultivation in three flat panel photobioreactors. High UASB efficiency was obtained in organic matter removal (> 90%), even with a large variability of initial mixture characteristics. C. sorokiniana production reached about 1 g L−1, with an average removal of dissolved inorganic carbon, orthophosphate and ammonia around 46 to 56%, 40 to 60% and 100%, respectively. Possible solutions to improve the microalgae growth and the system treatment are discussed.
•Effective anaerobic treatment of CPW using UASB reactors in series.•Effluent recirculation and proportion of nutrients provided operational stability.•Balanced amounts of acetate and ...hydrogen-utilizing methanogens at high OLR.•Proteobacteria and Candidatus Cloacimonetes increased in response to OLR variation.
The effect of the organic loading rate (OLR) on the performance and microbial composition of a two-stage UASB system treating coffee processing wastewater was assessed. The system was operated with OLR up to 18.2 g COD (L d)−1 and effluent recirculation. Methane production and effluent characteristics were monitored. The microbial composition was examined through next-generation sequencing and qPCR from the anaerobic sludge of the first reactor (R1) operated at low and high OLR. The system showed operational stability, obtaining a maximum methane production of 2.2 L CH4 (L d)−1, with a removal efficiency of COD and phenolic compounds of 84 and 73%, respectively. The performance of R1 at high OLR in steady conditions was associated with an appropriate proportion of nutrients (particularly Fe) and a marked increase of the syntrophic bacteria Syntrophus and Candidatus Cloacimonas, and acetoclastic and hydrogenotrophic methanogens, mainly Methanosaeta, Methanoculleus, Methanobacterium and Methanomassiliicoccus.
•Injection of axenic methanogens benefits temperature transition of UASB reactors.•Exogenous hydrogenotrophic methanogen can be confined to pre-existing granules.•Bioaugmentation promoted the growth ...of syntrophic acid oxidizers in granules.•Bioaugmented reactor produced maximum 40% more methane than abiotic augmentation.
The application of thermophilic conditions in anaerobic digesters leads to higher methane production rates and better sanitation of the effluents compared to mesophilic operation. However, an increase in operational temperature is challenging due to the tremendous selective pressure imposed on the microbial consortium. The adaptation of microbial community to a new environment or condition can be accelerated by a process known as “bioaugmentation” or “microbial community manipulation”, during which exogenous microorganisms harbouring specific metabolic activities are introduced to the reactor. The aim of the current study was to rapidly convert the operational temperature of up-flow anaerobic sludge blanket (UASB) reactors from mesophilic to thermophilic conditions by applying microbial community manipulation techniques. Three different bioaugmentation strategies were compared and it was proven that the injection of axenic methanogenic culture was the most efficient approach leading to improved biomethanation process with 40% higher methane production rate compared to the control reactor. Microbial community analyses revealed that during bioaugmentation, the exogenous hydrogenotrophic methanogen could be encapsulated in granular structures and concomitantly promote the growth of syntrophic fatty acid oxidizing bacteria. The results derived from the current study indicated that microbial community manipulation is an efficient alternative method to speed up transition of UASB reactors from mesophilic to thermophilic conditions.
Display omitted
•Electroactive bacteria enriched in UABE activate bDIET for methane production.•bDIET for methane production is less susceptible to low influent pH.•Effluent recirculation in UABE ...further improves bDIET for methane production.•UABE with effluent recirculation is a recommended process for distillery wastewater.
Methane production in the upflow anaerobic bioelectrochemical reactor (UABE) treating acidic distillery wastewater was compared to the upflow anaerobic sludge blanket reactor (UASB), and the electron transfer pathways for methane production were also evaluated in the effluent recirculation. The methane productions from reactors were influenced by the low pH of influent wastewater. However, the methane production rate and yield of the UABE were 2.08L/L.d and 320mL/g CODr, which were higher than the UASB. The effluent recirculation containing alkalinity neutralized the acidic influent and increased the upflow velocity in both reactors, and improved the direct interspecies electron transfer more in the UABE. When the effluent recirculation ratio was 3.0 in the UABE, the methane production rate and yield were reached up to 3.88L/L.d and 501.0mL/g CODr, respectively. The UABE requires electrode installation and electrical energy for operation, but the benefits from increased methane production are much higher.
Display omitted
•The impacts and indictors of SFDM formation in AnSFDMBR were extensively studied.•The SFDM could be formed after 60–90 min of operation in an optimum condition.•Humic acid was the ...dominant EPS in AnSFDMBR but without significant accumulation.•The polysaccharides percentage on the mesh was 2–3 times higher than that in sludge.•β-Polysaccharides attached along fibers and attributed to successful SFDM formation.
Self-forming dynamic membrane bioreactor (SFDMBR) technology has drawn increased attention recently, especially for its potential application in anaerobic conditions to retain slow growing sludge in the system. To attain maximum sludge retention, quick development of a self-forming dynamic membrane (SFDM) is deemed necessary. A lab-scale upflow anaerobic sludge blanket (UASB) reactor with a side-stream anaerobic SFDMBR was used in this study to investigate the factors affecting the successful formation of a SFDM and identify the indicators of success. The SFDM formed successfully within 60 to 90 min to produce permeates of less than 10 NTU after system optimization. The short formation period and low permeate turbidity provide strong support for the potential of retaining a large amount of sludge in the UASB reactor. The thickness and wet density of the SFDM increased continuously with the decrease in surface area during the formation period. Extracellular polymeric substances (EPS) played an essential role in SFDM formation. Humic acid was the dominant EPS in the sludge, but it did not significantly affect the SFDM formation. Even though polysaccharides only represented 3.7% of the total EPS in sludge, it accumulated on the supporting material as a percentage of the total EPS increased significantly from 6.2% after 60 min to 10.8% after 720 min. Therefore, polysaccharides were the primary reason for the formation of the SFDM. β-polysaccharides were more important because it mainly accumulated on the fiber of the supporting material.
PDF
