Sequencing Batch Reactor Research Articles

The Effect of Salinity on N2O Emissions during Domestic Wastewater Partial Nitrification Treatment in a Sequencing Batch Reactor

Previous studies have highlighted the salinization caused by the use of seawater to flush toilets and industrial wastewater entering the urban wastewater systems in coastal areas. Thus, in this study, the effect of salinity on N2O emissions during the partial nitrification process, as well as the emission mechanism, was investigated using a partial nitrification system of wastewater as the research object. The results showed that (1) the increase in salinity decreased the oxidation rate of NH4+ and the formation rate of NO2− during partial nitrification; (2) the increase in salinity increased the N2O emissions during NH4+ oxidation and NH2OH oxidation and decreased the formation rate of NO2−-N during hydroxylamine oxidation; (3) the total N2O emissions during hydroxylamine oxidation were less than those during ammonia nitrogen oxidation, and a greater amount of NO2− was reduced to N2 instead of N2O during hydroxylamine oxidation; and (4) a novel finding was that, during partial nitrification with the available organic matter, the N2O emissions via heterotrophic denitrification by heterotrophic bacteria should not be ignored, and the increase in salinity can increase the N2O emissions generated via heterotrophic denitrification. These results would provide a theoretical basis for reducing the N2O emissions in the wastewater treatment process.

The effects of didodecyl dimethyl ammonium chloride on microbial communities and resistance genes in floc, granular and biofilm denitrification sludge

As a type of quaternary ammonium compounds, didodecyl dimethyl ammonium chloride (DADMAC C12) was frequently detected in wastewater treatment plants. Here, floc-based sequencing batch reactor (FSBR), granule-based SBR (GSBR) and biofilm SBR (BSBR) were fed with 0.5, 5 and 10 mg/L of DADMAC C12 for 120 d. Compared with floc sludge and granule sludge, biofilm had the strongest ability to resist the impact of DADMAC C12. Notably, in both FSBR and GSBR systems, 5 mg/L DADMAC C12 promoted denitrification sludge to become hydrophobic and compact due to an increase in α-Helix/(β-Sheet+Random coil), consequently enhancing sludge granulation. Besides，high concentration of DADMAC C12 generally increased the abundances of MGEs in three denitrification systems, except extracellular MGEs in water. The variation of efflux pump ARGs was basically consistent with that of MGEs. The stimulation of DADMAC C12 also increased significantly the abundance of extracellular antibiotics deactivation ARGs in water in three denitrification systems. Besides, DADMAC C12 induced co-selection among various ARGs and promoted the proliferation and spread of sulfonamide ARGs in water.

Deterioration of sludge characteristics and promotion of antibiotic resistance genes spread with the co-existing of polyvinylchloride microplastics and tetracycline in the sequencing batch reactor

With the continuous increase in microplastics (MPs) and tetracycline (TC) entering wastewater treatment plants (WWTPs) along with sewage, the co-existence of MPs and TC in the biological treatment of wastewater has attracted extensive attention. This study investigated the effect of 1 mg/L polyvinyl chloride (PVC) MPs and 100 ng/L TC co-existing on sequencing batch reactors (SBRs) (S2) treating phenol wastewater in contrast to the control with TC alone (S1). The phenol removal efficiency was significantly inhibited by the co-existence of PVC MPs and TC. Sludge characteristics were also distinctively influenced. The decreased zone sludge velocity (ZSV) and increased sludge volume index (SVI) indicated that the combined effect of PVC MPs and TC deteriorated sludge settleability, which had positive and negative linear correlations with extracellular polymeric substances (EPS) content and the protein (PN)/polysaccharide (PS) ratio, respectively. Moreover, the decreased and increased relative abundances of potential phenol-degraders and antibiotic resistance gene (ARG) carriers may elucidate the inhibition of phenol removal and promotion of ARGs propagation with the co-occurrence of PVC MPs and TC. In addition, the enhanced potential ARGs hosts, loss of the EPS protective effect, and increased membrane permeability induced by reactive oxygen species (ROS) jointly promoted ARGs dissemination in the co-existence of PVC MPs and TC. Notably, the co-occurrence of ARGs and mobile genetic element (MGEs) indicated that the co-existence of PVC MPs and TC promoted the spread of some transposase-associated ARGs mediated by horizontal gene transfer (HGT).

Corrigendum: Biodegradation of 2-4-6 trichlorophenol by sequencing batch reactors (SBR) equipped with a rotating biological bed and operated in an anaerobic-aerobic condition

Corrigendum: Biodegradation of 2-4-6 trichlorophenol by sequencing batch reactors (SBR) equipped with a rotating biological bed and operated in an anaerobic-aerobic condition

Metagenomics, metatranscriptomics, and proteomics reveal the metabolic mechanism of biofilm sequencing batch reactor with higher phosphate enrichment capacity under low phosphorus load

The biofilm sequencing batch reactor (BSBR) process has higher phosphate recovery efficiency and enrichment multiple when the phosphorus load is lower, but the mechanism of phosphate enrichment at low phosphorus load remains unclear. In this study, we operated two BSBR operating under low and high phosphorus load (0.012 and 0.032 kg/(m3·d)) respectively, and used metagenomic, metatranscriptomic, and proteomics methods to analyze the community structure of the phosphorus accumulating organisms (PAOs) in the biofilm, the transcription and protein expression of key functional genes and enzymes, and the metabolism of intracellular polymers. Compared with at high phosphorus load, the BSBR at low phosphorus load have different PAOs and fewer types of PAOs, but in both cases the PAOs must have the PHA, PPX, Pst, and acs genes to become dominant. Some key differences in the metabolism of PAOs from the BSBR with different phosphorus load can be identified as follows. When the phosphorus load is low, the adenosine triphosphoric acid (ATP) and NAD(P)H in the anaerobic stage come from the TCA cycle and the second half of the EMP pathway. The key genes that are upregulated include GAPDH, PGK, ENO, ppdk in the EMP pathway, actP in acetate metabolism, phnB in polyhydroxybutyrate (PHB) synthesis, and aceA, mdh, sdhA, and IDH1 in the TCA cycle. In the meantime, the ccr gene in the PHV pathway is inhibited. As a result, the metabolism of the PAOs features low glycogen with high PHB, Pupt, Prel, and low PHV. That is, more ATP and NAD(P)H flow to phosphorus enrichment metabolism, thus allowing the highly efficient enrichment of phosphorus from low concentration phosphate thanks to the higher abundance of PAOs. The current results provide theoretical support and a new technical option for the enrichment and recovery of low concentrations of phosphate from wastewater by the BSBR process.

Extracellular polymeric substances and microbial community shift during the start-up of a single-stage partial nitritation/anammox process.

A sequencing batch reactor (SBR) was operated to investigate variations of extracellular polymeric substances (EPS) and microbial community during the start-up of the single-stage partial nitritation/anammox (SPN/A) process at intermittent aeration mode. The SPN/A system was successfully started on day 34, and the nitrogen removal efficiency and total nitrogen loading rate were 82.29% and 0.31 kg N/(m3 ·d), respectively. Furthermore, the relationship between the protein secondary structures and microbial aggregation was strongly related. The α-helix/ (β-sheet + random coil) ratios increased obviously from 0.20 ± 0.03 to 0.23 ± 0.01, with the sludge aggregation mean size increased from 56 to 107 μm during the start-up of SPN/A. During the start-up of SPN/A, Candidatus Kuenenia was the primary anammox bacteria, whereas Nitrospira was the main functional bacteria of nitrite-oxidizing bacteria. Correlation between the microbial community and EPS components was performed. The EPS and microbial community played important roles in keeping stable nitrogen removal and the formation of sludge granules.

Improving Nitrogen Removal Efficiency in SBR Reactors by Controlling Operational Phases

Wastewater treatment facilities using the activated sludge process are the most widely used solutions worldwide, regardless of the region. According to statistics, the most common option for Vietnam’s conditions is the sequenced batch reactor, which is used at a third of wastewater treatment plants (WWTP). Thus, studies of treatment processes in SBRs that seek high-quality treatment may have a wide range of further applications in practice. Another reason is that wastewater treated to meet Vietnamese standards has a significant negative impact on water resources. The research was carried out in relation to Hoaxuan wastewater treatment plants, where pilot models were installed that worked on influent wastewater. Studies of the nitrification process in SBRs (cycle duration 4 h) have shown that the highest efficiency of removal of pollutants (organic pollution by 90%, ammonium nitrogen by 80%) is achieved at a pH value close to 8.0. The increase in pH also had a positive effect on the increase in the specific rate of nitrification. At the second stage of the research, the process of denitrification in SBRs (cycle duration of 6.5 h) was considered. The results demonstrated that treatment quality corresponded to the standards for the Russian Federation, which are stricter than Vietnamese standards (3.0 mg/L vs. 30 mg/L of biochemical oxygen demand; 0.4 mg/L vs. 5 mg/L of ammonium nitrogen). For the second part of the study, a specific denitrification rate was determined in order to establish its dependence on the main parameters of the SBR model performance.

Evaluating the Operation of a Full-Scale Sequencing Batch Reactor–Reverse Osmosis–Evaporation System Used to Treat Landfill Leachates: Removal of Pollutants, Energy Consumption and Greenhouse Gas Emissions

Limited information is available in the literature regarding the energy consumption and the greenhouse gases emitted during landfill leachates treatment. A full-scale landfill leachates treatment system that included primary sedimentation, biological treatment in sequencing batch reactors, reverse osmosis and mechanical vapor recompression evaporation was monitored and evaluated for the removal of major pollutants, energy consumption and greenhouse gas emissions. Samples were taken during a period of two years from different points of the system, while the actual power consumption was calculated considering the available mechanical equipment and the hours of operation. The quantities of greenhouse gases emitted were estimated using appropriate equations and based on the operational characteristics of the system. According to chemical analyses, biological treatment resulted in partial removal of COD and total nitrogen, while the removal of BOD5 and NH4-N was significant, reaching 90 and 98%, respectively. Use of reverse osmosis increased the removal of all pollutants, satisfying the requirements of the legislation on wastewater discharge into the environment. Power consumption was calculated to be 35.3 KWhr per m3 of treated leachate, while mechanical vapor recompression evaporation was responsible for 60.5% of the total energy required. The contribution of other processes to energy consumption was as follows, in decreasing order: sequencing batch reactors > reverse osmosis > primary treatment. The roots blower vacuum pump used for mechanical vapor recompression evaporation, and the blowers providing air to the sequencing batch reactors, were the most energy-intensive pieces of apparatus, contributing 44.2% and 11.3% of the required energy, respectively. The quantity of greenhouse gases emitted was estimated to be 27.7 Kg CO2eq per m3 of treated leachates. Among the different processes used, biological treatment and mechanical vapor recompression evaporation contributed to 45.7% and 44.1% of the total emissions, respectively. The findings of this study reveal that an integrated landfill leachate treatment system that combines biological treatment and reverse osmosis can assure the protection of the aquatic environment by producing high-quality effluent; however, further research should be conducted regarding the sustainable management of reverse osmosis concentrate. Mechanical vapor recompression evaporation contributes significantly to the environmental footprint of the landfill leachates treatment system due to both high energy consumption and elevated emissions of greenhouse gases.

Advanced steam-explosion pretreatment mediated anaerobic digestion of municipal sludge: Effects on methane yield, emerging contaminants removal, and microbial community

Advanced steam explosion pretreatment, i.e., the Thermal hydrolysis process (THP) is applied mainly to improve the sludge solubilization and subsequent methane yield in the downstream anaerobic digestion (AD) process. However, the potential of THP in pretreating the high solids retention time (SRT) sludges, mitigating the risk of emerging organic micropollutants and effects on anaerobic microbiome in digester remains unclear. In this study, sludge from a sequencing batch reactor (SBR) system operating at a SRT of 40 days was subjected to THP using a 5 L pilot plant at the temperature ranges of 120–180 °C for 30–120 min. The effect of THP on organics solubilization, methane yield, organic micropollutant removal, and microbial community dynamics was studied. The highest methane yield of 507 mL CH4/g VSadded and volatile solids (VS) removal of 54% were observed at 160°C- 30min THP condition, i.e., 4.1 and 2.6 times higher than the control (123 mL CH4/gVSadded, 20.7%), respectively. The experimental values of hydrolysis coefficient and methane yield have been predicted using Modified Gompertz, First order, and Logistics models. The observed values fitted well with all three models showing an R2 value between 0.96 and 1.0. THP pretreated sludges showed >80% removal of Trimethoprim, Enrofloxacin, Ciprofloxacin, and Bezafibrate. However, Carbamazepine, 17α-ethinylestradiol, and Progesterone showed recalcitrant behavior, resulting in less than 50% removal. Microbial diversity analysis showed the dominance of Proteobacteria, Firmicutes, Chloroflexi, and Bacteroidetes, collectively accounting for >70–80% of bacterial reads. They are mainly responsible for the fermentation of complex biomolecules like polysaccharides, proteins, and lipids. The THP-mediated anaerobic digestion of sludge shows better performance than the control digestion, improved methane yield, higher VS and micropollutants removal, and a diverse microbiome in the digester.

Leveraging anaerobic biodegradation of tetracycline in anaerobic digestion systems with different operational modes

Antibiotics such as tetracycline in wastewater may cause the operation failure of anaerobic digestion systems. With two types of operational modes, continuous-flow reactors (CFRs) and sequencing batch reactors (SBRs) were operated with or without the addition of tetracycline to examine the influence of tetracycline on system performance, tetracycline removal, metabolic activity, and microbial communities. Tetracycline inhibited the removal of chemical oxygen demand (COD) by 23.9% in CFRs and 20.5% in SBRs, and led to the accumulation of volatile fatty acids (VFAs). Also, the maximum methane production rate was inhibited by 24.5% in CFRs and 48.8% in SBRs due to the existence of tetracycline, while the maximum methane production was reduced by 32.8% in CFRs and 13.8% in SBRs. CFRs exhibited a better recovery capacity during COD shock loading and demonstrated superior propionate degradation and methane production capabilities. Moreover, CFRs achieved better tetracycline removal capacity compared to SBRs. Biodegradation was found to be the dominant tetracycline removal pathway, accounting for 88.9% (CFRs) and 82.0% (SBRs). Long-term exposure to tetracycline decreased archaea abundances and inhibited the enrichment of hydrolytic-acidogenic bacteria (Mesotoga and Syner-01). Meanwhile, CFRs provided a more conducive environment for the enrichment of these microorganisms. The presence of Geobacter in conjunction with the detected ethanol in batch experients of CFRs suggested the potential presence of direct interspecies electron transfer, elucidating the enhanced pollutant removal of CFRs. Additionally, Trichococcus, a genus associated with tetracycline removal, was found to be highly enriched with the long-term dosage of tetracycline.

Treatment performance and microbial community structure in an aerobic granular sludge sequencing batch reactor amended with diclofenac, erythromycin, and gemfibrozil.

This study characterizes the effects of three commonly detected pharmaceuticals-diclofenac, erythromycin, and gemfibrozil-on aerobic granular sludge. Approximately 150 μg/L of each pharmaceutical was fed in the influent to a sequencing batch reactor for 80 days, and the performance of the test reactor was compared with that of a control reactor. Wastewater treatment efficacy in the test reactor dropped by approximately 30-40%, and ammonia oxidation was particularly inhibited. The relative abundance of active Rhodocyclaceae, Nitrosomonadaceae, and Nitrospiraceae families declined throughout exposure, likely explaining reductions in wastewater treatment performance. Pharmaceuticals were temporarily removed in the first 12 days of the test via both sorption and degradation; both removal processes declined sharply thereafter. This study demonstrates that aerobic granular sludge may successfully remove pharmaceuticals in the short term, but long-term tests are necessary to confirm if pharmaceutical removal is sustainable.

Settling velocity of algal-bacterial granular sludge studied in the sequence batch reactor

Granule settling velocity is critical to biosolids-liquid separation. The settling velocity of algal-bacterial granules versus the diameter of granules was examined as a function of granule diameter in the sequence batch reactor in eleven days of cultivation. Despite granules having an apparently compact and rounded shape and considerable scatter of the data, the results never showed granules are homogeneously dense packed structures in the range of 10 μm to 1.0 mm in diameter. The settling velocity increases with granule size. The estimated fractal dimension was always less than two. The result was interpreted as forming heterogeneous compact layered structures in the shell from the early stage of cultivation rather than rearrangement from a bulk floc into a dense structure. Additional analysis for the cultivation of 150 days confirmed the considerable growth of size and fluffy hair. However, the settleability of small fragments remained relatively the same as heterogeneous compact structures.

Utilization of first-order mass action kinetic models to elucidate the mechanism of methane fermentation of glycerol

Knowledge-driven models can aid in understanding the underlying mechanism of methane fermentation, however, these models are often too complex. We proposed to utilize first-order mass action kinetic models as a simpler alternative to conventional knowledge-driven models for gaining some insights on the mechanism of methane fermentation. The data used for model fitting were obtained from a methane fermentation experiment using anaerobic sequencing batch reactor (ASBR) with glycerol as a substrate. Incorporation of substrate feeding profile into the model improved fitness to the data especially during the early stage of the feeding cycle. Model with the assumption that glycerol was metabolized into both propionic and acetic acid and methane was produced via both propionic and acetic acid showed the best fit (root-mean square error = 0.0012), which suggested that the mechanism of the glycerol methane fermentation might follow that particular path. The difference in the applicability of the models on several feed profiles used in this experiment suggested that the mechanism can be different for each feed profile, which was supported by the microbial consortium data. These findings showed the possibility to use first-order mass action kinetic models as a simpler alternative to study the mechanism of methane fermentation of glycerol.

Influencing factors on the activity of an enriched Nitrospira culture with granular morphology

ABSTRACT Nitrospira is a common genus of nitrite-oxidising bacteria (NOB) found in wastewater treatment plants (WWTPs). To identify the key factors influencing the composition of NOB communities, research was conducted using both sequencing batch reactor (SBR) and continuous flow reactor under different conditions. High-throughput 16S rRNA gene sequencing revealed that Nitrospira (18.79% in R1 and 25.77% in R3) was the dominant NOB under low dissolved oxygen (DO) and low nitrite ( NO 2 − -N) concentrations, while Nitrobacter (21.26% in R2) was the dominant NOB under high DO and high NO 2 − -N concentrations. Flocculent and granule sludge were cultivated with Nitrospira as the dominant genus. Compared to Nitrospira flocculent sludge, Nitrospira granule sludge had higher inhibition threshold concentrations for free ammonia (FA) and free nitrous acid (FNA). It was more likely to resist adverse environmental disturbances. Furthermore, the effects of environmental factors such as temperature, pH, and DO on the activity of Nitrospira granular sludge were also studied. The results showed that the optimum temperature and pH for Nitrospira granular sludge were 36°C and 7.0, respectively. Additionally, Nitrospira granular sludge showed a higher dissolved oxygen half-saturation constant (Ko) of 3.67 ± 0.71 mg/L due to its morphological characteristics. However, the majority of WWTPs conditions do not meet the conditions for the Nitrospira granular sludge. Thus, it can be speculated that future development of aerobic partial nitrification granular sludge may automatically eliminate the influence of Nitrospira. This study provides a theoretical basis for a deeper understanding of Nitrospira and the development of future water treatment processes.

Performance evaluation, enzymatic activity change and metagenomic analysis of sequencing batch reactor under divalent zinc stress

Divalent zinc (Zn2+) are widely detected in domestic and industrial wastewater, and it is essential to evaluate the effect of Zn2+ on wastewater biological treatment process due to its bio-toxicity. In this study, the nitrogen removal rates and their corresponding enzymatic activities of sequencing batch reactor decreased with the increase of Zn2+ concentration. The Zn2+ accumulation in activated sludge caused significant antioxidant response, and the reactive oxygen species (ROS) production and antioxidant enzymatic activities were positively correlated with Zn2+ concentration. The presence of Zn2+ inhibited the metabolic pathways related to energy production and electron transport. The abundance decreases of nitrification and denitrification functional genes led to the deterioration of nitrogen removal performance under Zn2+ stress. The correlation analysis between functional gene modules and microbial genera revealed that Zoogloea had obvious Zn2+ resistance. This study can provide the insights into the influencing mechanism of Zn2+ on the biological nitrogen removal process.

Nitrite accumulation in activated sludge through cyclic anaerobic exposure with acetate

Achieving nitrite accumulation still remains challenging for efficient short-cut biological nitrogen removal in municipal wastewater treatment. To tackle the problem of insufficient carbon in incoming wastewater for biological nutrient removal, a return activated sludge (RAS) fermentation method has been proposed and demonstrated to enable producing supplemental volatile fatty acids (VFAs) and enhance biological phosphorus removal via sludge cycling between mainstream and a sidestream anaerobic reactor. However, the impacts of long anaerobic exposure with acetate on nitrifying bacteria, known as the aerobic chemoautotrophic microorganisms, remains unexplored. In this study, the activated sludge underwent a cyclic anaerobic treatment with the addition of acetate (Ac), the effects on nitrification rate, abundance and microdiversity of nitrifying communities were comprehensively assessed. Firstly, batch activity tests proved the direct addition of high acetate (above 1000 mg/L) could cause inhibition on the nitrification rate, moreover, the inhibitory effect was stronger on nitrite-oxidizing bacteria (NOB) activity than that of ammonia-oxidizing bacteria (AOB). Then, a sequencing batch reactor (SBR) was applied to test the nitrogen conversion performance for low-strength ammonium wastewater. Nitrite accumulation could be achieved via the cyclic anaerobic exposure with 1000–5000 mg Ac/L. The maximum effluent concentration of nitrite was 40.8 ± 3.5 mg N/L with nitrite accumulation ratio (NAR) of 67.6 ± 3.5%. The decrease in NOB activity (72.7%) was greater than AOB of 42.4%, promoting nitrite accumulation via nitritation process. Furthermore, the cyclic anaerobic exposure with acetate can largely reshape the nitrifying communities. As the dominant AOB and NOB, the abundance of Nitrosomonas and Nitrospira were both decreased with species-level microdiversity in the nitrifying communities. However, the heterotrophic microorganism, Thauera, were found to be highly enriched (from 0 to 17.3%), which may act as the potential nitrite producer as proved by the increased nitrate reduction gene abundance. This study can provide new insights into achieving mainstream nitrite accumulation by involving sidestream RAS fermentation towards efficient wastewater treatment management.

Combination of sequencing batch reactor activated sludge process with sludge lysis using thermophilic bacterial community for minimizing excess sludge

Sludge reduction is a major challenge in biological wastewater treatment. Hydrolytic enzymes secreted by thermophilic bacteria can lyse sludge and thus achieve sludge reduction, and the indigenous thermophilic community in sludge can lyse sludge more effectively. In this study, the feasibility of combining a sludge lysis reactor based on thermophilic bacteria community (LTBC reactor, 75 °C) with a conventional sequencing batch activated sludge reactor (SBR) for sludge reduction (i.e., LTBC-SBR process) was systematically investigated first time. The effect of lysed sludge returning to the biochemical tank on pollutant removal efficiency, sludge flocculation, sludge settling, and microbial community and function of the LTBC-SBR process was studied. In the LTBC1-SBR process, a sludge growth rate of 0.71 g TSS/day was observed when the lysed sludge reflux ratio (LRR) was 1, and the sludge generation was reduced by 81.5% compared to the conventional SBR reactor. In the LTBC1-SBR process, the removal efficiencies of chemical oxygen demand and total nitrogen were 94.0% and 80.5%, respectively. There was no significant difference in the sludge volume index from the SBR to the LTBC1-SBR stage, however, the effluent suspended solids concentration increased from 35.2 ± 2.1 mg/L to 80.1 ± 5.3 mg/L. This was attributed to the reflux of sludge lysate. In addition, the changes in extracellular polymers content and composition resulted in poor sludge flocculation performance. Heterotrophic bacteria associated with Actinobacteria and Patescibacteria enriched in LTBC1-SBR with relative abundance of 28.51 ± 1.25% and 20.01 ± 1.21%, respectively, which decomposed the macromolecules in the refluxed lysed sludge and contributed to the sludge reduction. Furthermore, due to the inhibition of nitrite-oxidizing bacteria, the nitrite concentration in the effluent of the LTBC1-SBR system reached 4.7 ± 1.1 mg/L, and part of the denitrification process was achieved by short-cut nitrification and simultaneous denitrification. These results indicate that in-situ sludge reduction technology based on lyse sludge lysing by thermophilic community has considerable potential to be widely used in wastewater treatment.

Evaluation of the anaerobic digestion of winery wastewater: Effect of fly ash in anaerobic sequencing batch reactor

The addition of fly ash (FA) to an anaerobic reactor has been studied mainly in batch tests. Nevertheless, the FA effect on the continuous operation of an anaerobic bioreactor has not been addressed. Therefore, the present work shows the effect of FA on the continuous operation of anaerobic sequencing reactors (ASBRs) treating winery wastewater. Two ASBRs were used and operated continuously for 302 days under mesophilic conditions with a hydraulic retention time (HRT) of 3 days. The effect of the organic loading rate (ORL) on the operation was investigated for 204 days. After that, to evaluate the effect of FA as an anaerobic digestion (AD) enhancer, one of the reactors was dosed with 25 mg L−1 of FA for 98 days. The FA dosages allowed an increase in methane production and organic matter removal by 75% and 42%, respectively, concerning the system without FA. Furthermore, the importance of FA in the process was demonstrated by obtaining a yield of 334 NmL CH4 COD removed−1. This result represented a 12% increase compared to the yield previously obtained in the same reactor before adding the FA. Additionally, acetic acid and propionic acid were the predominant volatile fatty acids (VFAs) in the process. Finally, the metals present in the digested sludge after FA addition did not exceed the limits allowed by Chilean legislation.

Recovery of Energy and Carbon Dioxide from Craft Brewery Wastes for Onsite Use

Interest in craft beers is increasing worldwide due to their flavor and variety. However, craft breweries have high water, energy, and carbon dioxide (CO2) demands and generate large quantities of high-strength waste and greenhouse gases. While many large breweries recover energy using anaerobic digestion (AD) and recapture CO2 from beer fermentation, little is known about the economic feasibility of applying these technologies at the scale of small craft breweries. In addition, compounds in hops (Humulus lupulus), which are commonly added to craft beer to provide a bitter or “hoppy” flavor, have been shown to adversely affect anaerobic microbes in ruminant studies. In this study, biochemical methane potential (BMP) assays and anaerobic sequencing batch reactor (ASBR) studies were used to investigate biomethane production from high-strength craft brewery waste, with and without hop addition. A spreadsheet tool was developed to evaluate the economic feasibility of bioenergy and CO2 recovery depending on the brewery’s location, production volume, waste management, CO2 requirement, energy costs, and hop waste addition. The results showed that co-digestion of yeast waste with 20% hops (based on chemical oxygen demand (COD)) resulted in slightly lower methane yields compared with mono-digestion of yeast; however, it did not significantly impact the economic feasibility of AD in craft breweries. The use of AD and CO2 recovery was found to be economically feasible if the brewery’s annual beer production is >50,000 barrels/year.

Efficient conversion of wine lees into medium-chain carboxylic acids by mixed culture using an in-line extraction system

This study evaluates a process to generate medium-chain carboxylic acids (MCCA) from wasted wine lees. The effect of pH, feeding mode, organic loading rate, and the in-line extraction of the acids on the MCCA production rate was evaluated. Both the electron donor (ethanol) and acceptor (acetate) were generated in situ from the waste. First, the reactor was operated as a sequencing batch reactor (SBR), and pH 5.5 and 5.2 were evaluated. The caproate productivity was ten times higher at pH 5.5 than at 5.2. An in-line extraction system was next implemented, and the operation as SBR and the continuous mode was studied. The continuous mode allowed an increase of the residual ethanol; however, the feeding with concentrated wine lees caused an acetate over-accumulation. Caprylate was produced and extracted over caproate (caprylate/caproate ratio of 1.2) by avoiding the bioreactor overload and keeping a low ethanol broth concentration. In conclusion, the maximal MCCA production rate (143.4 ± 14.8 mmol C/L-d) was obtained when the organic loading rate was gradually increased in the continuous operation; under such conditions, Eubacterium pyruvativorans predominated. The in-line extraction system allowed the production and recovery of MCCA.