Food Waste-recycling Wastewater Research Articles

Application of endospore-forming Bacillus species to food waste-recycling wastewater treatment: A focus on the fate of macromolecular nutrients

A novel bioprocess for treating high-strength food waste-recycling wastewater (FRW) by using endospore-forming bacteria was developed and evaluated under various hydraulic retention times (HRTs) and sequentially decreasing dissolved oxygen (DO) concentrations. Four Bacillus species (i.e., B. subtilis, B. licheniformis, B. mycoides, and B. thuringiensis) were added to the laboratory-scale system operated for 200 days and fed with an influent of 30 g·BOD/L. The dominance of endospore-forming bacteria was achieved (> 65%) by adding Bacillus species, which decomposes macromolecular nutrients such as carbohydrates, proteins, and lipids. Longer HRT in the aerobic reactor led to a higher removal rate of organic matter, whereas endospore-forming bacteria were clearly identified in the anoxic reactor; the observed removal efficiency of carbohydrates, lipids, proteins, nitrogen, and phosphorus were 99.4%, 94.0%, 87.6%, 81.3%, and 91.4%, respectively, throughout the sequential aerobic-anaerobic reactors. The results show that the proposed system using endospore-forming Bacillus bacteria could be an effective alternative for high-strength FRW treatment.

Linking process performances and core microbial community structures in anaerobic membrane bioreactor with rotatory disk (ARMBR) system fed with high-strength food waste recycling wastewater

This study first evaluated the process performances and microbial community structures of anaerobic rotary membrane bioreactor (ARMBR) fed with food waste recycling wastewater (FRW). Three identical ARMBRs were operated under different organic loading rate (OLR) conditions (1.5, 3.0, and 6.0 kg COD m−3 d−1) after the same start-up periods. The start-up performances and archaeal community structures differed among the ARMBRs, probably due to the sudden OLR shock. After the start-up, bio-methane was stably produced until the end of the operational period, with all of the ARMBRs showing >95% COD removal efficiency. Methanosaeta spp. was the predominant methanogen; diverse hydrogenotrophic methanogens co-existed. Bacteroidetes-like bacteria and Candidatus Cloacamonas acted as major fermentative bacteria producing acetate or hydrogen for the growth of methanogens. The results suggest that our ARMBR system can be a promising option to manage high-strength organic wastewater such as FRW.

Process stability and comparative rDNA/rRNA community analyses in an anaerobic membrane bioreactor with silicon carbide ceramic membrane applications

This study evaluated the feasibility of using a silicon carbide (SiC) anaerobic ceramic membrane bioreactor (AnCMBR) to co-manage domestic wastewater (DWW) and food waste recycling wastewater (FRW). A pilot-scale SiC-AnCMBR was put into operation for 140 days under two different organic loading rates (OLRs): 5 kg COD m−3 d−1 (OLR 5) and 3 kg COD m−3 d−1 (OLR 3). The organic removal efficiency was 93.5 ± 3.7% over the operational period. Methane production increased significantly after sludge re-seeding at OLR 3. rDNA and rRNA microbial results showed that the active archaeal community was affected by sludge re-seeding, whereas the active bacterial community was not, indicating that a shift in the active archaeal community was responsible for the increased methane production. Our results thus suggest that SiC-AnCMBRs are a promising option for co-managing DWW and FRW.

Comprehensive analysis of microbial communities in full-scale mesophilic and thermophilic anaerobic digesters treating food waste-recycling wastewater

Microbes were sampled for a year in a full-scale mesophilic anaerobic digester (MD) and a thermophilic anaerobic digester (TD) treating food waste-recycling wastewater (FRW), then microbial community structure, dynamics and diversity were quantified. In the MD, Fastidiosipila, Petrimonas, vadinBC27, Syntrophomonas, and Proteiniphilum were dominant bacterial genera; they may contribute to hydrolysis and fermentation. In the TD, Defluviitoga, Gelria and Tepidimicrobium were dominant bacteria; they may be responsible for hydrolysis and acid production. In the MD, dominant methanogens changed from Methanobacterium (17.1 ± 16.9%) to Methanoculleus (67.7 ± 17.8%) due to the increase in ammonium concentration. In the TD, dominant methanogens changed from Methanoculleus (42.8 ± 13.6%) to Methanothermobacter (49.6 ± 11.0%) due to the increase of pH. Bacteria and archaea were more diverse in the MD than in the TD. These results will guide development of microbial management methods to improve the process stability of MD and TD treating FRW.

Effects of changes in temperature on treatment performance and energy recovery at mainstream anaerobic ceramic membrane bioreactor for food waste recycling wastewater treatment

An anaerobic ceramic membrane bioreactor (AnCMBR) has been attracted as an alternative technology to co-manage various organic substrates. This AnCMBR study investigated process performance and microbial community structure at decreasing temperatures to evaluate the potential of AnCMBR treatment for co-managing domestic wastewater (DWW) and food waste-recycling wastewater (FRW). As a result, the water flux (≥6.9 LMH) and organic removal efficiency (≥98.0%) were maintained above 25 °C. The trend of methane production in the AnCMBR was similar except for at 15 °C. At 15 °C, the archaeal community structure did not shifted, whereas the bacterial community structure was changed. Various major archaeal species were identified as the mesophilic methanogens which unable to grow at 15 °C. Our results suggest that the AnCMBR can be applied to co-manage DWW and FRW above 20 °C. Future improvements including psychrophilic methanogen inoculation and process optimization would make co-manage DWW and FRW at lower temperature climates.

Use of food waste-recycling wastewater as an alternative carbon source for denitrification process: A full-scale study

Using organic wastes as an alternative to commercial carbon sources could be beneficial by reducing costs and environmental impacts. In this study, food waste-recycling wastewater (FRW) was evaluated as an alternative carbon source for biological denitrification over a period of seven months in a full-scale sewage wastewater treatment plant. The denitrification performance was stable with a mean nitrate removal efficiency of 97.2%. Propionate was initially the most persistent volatile fatty acid, but was completely utilized after 19days. Eubacteriacea, Saprospiraceae, Rhodocyclaceae and Comamonadaceae were the major bacterial families during FRW treatment and were regarded as responsible for hydrolysis (former two) and nitrate removal (latter two) of FRW. These results demonstrate that FRW can be an effective external carbon source; process stabilization was linked to the acclimation and function of bacterial populations to the change of carbon source.

Treatment of food waste recycling wastewater using anaerobic ceramic membrane bioreactor for biogas production in mainstream treatment process of domestic wastewater

A bench-scale anaerobic membrane bioreactor (AnMBR) equipped with submerged flat-sheet ceramic membranes was operated at mesophilic conditions (30–35 °C) treating domestic wastewater (DWW) supplemented with food wasterecycling wastewater (FRW) to increase the organic loading rate (OLR) for better biogas production. Coupling ceramic membrane filtration with AnMBR treatment provides an alternative strategy for high organic wastewater treatment at short hydraulic retention times (HRTs) with the potential benefits of membrane fouling because they have a high hydrophilicity and more robust at extreme conditions. The anaerobic ceramic MBR (AnCMBR) treating mixture of actual FRW with DWW (with an influent chemical oxygen demand (COD) of 2,115 mg/L) was studied to evaluate the treatment performance in terms of organic matter removal and methane production. COD removal during actual FRW with DWW operation averaged 98.3 ± 1.0% corresponding to an average methane production of 0.21 ± 0.1 L CH4/g CODremoved. Biogas sparging, relaxation and permeate back-flushing were concurrently employed to manage membrane fouling. A flux greater than 9.2 L m−2 h−1 (LMH) was maintained at 13 h HRT for approximately 200 days without chemical cleaning at an OLR of 2.95 kg COD m−3 d−1. On day 100, polyvinyl alcohol (PVA)-gel beads were added into the AnCMBR to alleviate the membrane fouling, suggesting that their mechanical scouring effect contributed positively in reducing the fouling index (FI). Although these bio-carriers might accelerate the breaking up of bio-flocs, which released a higher amount of soluble microbial products (SMP), a 95.4% SMP rejection was achieved. Although the retention efficiency of dissolved organic carbons (DOC) was 91.4% across the ceramic membrane, a meaningful interpretation of organic carbon detection (OCD) fingerprints was conducted to better understand the ceramic membrane performance.

Characterization of antibiotic resistance genes in representative organic solid wastes: Food waste-recycling wastewater, manure, and sewage sludge.

In this research, the distribution of antibiotic resistance genes (ARGs) was characterized in representative organic solid waste (OSW) in Korea: food waste-recycling wastewater (FRW), manure, and sewage sludge. The amounts of total ARG (gene copies/16S rRNA gene copies) was greatest in manure followed by sewage sludge and FRW. Interestingly, there were significantly different patterns in the diversity and mechanisms of ARGs. For example, a significant proportion of ARGs were tetracycline resistant genes in all the OSW (40.4-78.2%). β-lactam antibiotics resistant genes were higher in the FRW samples than in other types of OSW but sulfonamides resistant genes represented the greatest proportion in sludge. Regarding the characteristics of antibiotic resistance mechanisms, there was a relatively higher proportion of the ribosomal protection mechanism to tetracycline observed in the FRW and manure samples. However, tetracycline resistant genes with direct interaction were relatively higher in the sewage sludge samples. sul1 was the dominant subtype in all the OSW types and detection of ermB was observed although there was no ermC detected in sewage sludge. There were significant correlations between the occurrences of ARG subtypes: tetB and tetG in all OSW (P<0.01); tetE and tetQ only in sludge (P<0.01). The Class 1 integron-integrase gene (intI1) was significantly correlated with total ARGs only in manure and sludge (P<0.05), revealing potential horizontal gene transfer in these OSW.

Mesophilic Acidogenesis of Food Waste-Recycling Wastewater: Effects of Hydraulic Retention Time, pH, and Temperature.

The effects of hydraulic retention time (HRT), pH, and operating temperature (T OP) on the degradation of food waste-recycling wastewater (FRW) were investigated in laboratory-scale hydrolysis/acidogenesis reactors. Response surface analysis was used to approximate the production of volatile organic acids and degradation of volatile suspended solids (VSS), carbohydrate, protein, and lipid with regard to the independent variables (1 ≤ HRT ≤ 3days, 4 ≤ pH ≤ 6, 25 ≤ T OP ≤ 45°C). Partial cubic models adequately approximated the corresponding response surfaces at α < 5%. The physiological conditions for maximum acidification (0.4g TVFA + EtOH/gVSadded) and the maximal degradation of VSS (47.5%), carbohydrate (92.0%), protein (17.7%), and lipid (73.7%) were different. Analysis of variance suggested that pH had a great effect on the responses in most cases, while T OP and HRT, and their interaction, were significant in some cases. Denaturing gradient gel electrophoresis analysis revealed that Sporanaerobacter acetigenes, Lactobacillus sp., and Eubacterium pyruvivorans-like microorganisms might be main contributors to the hydrolysis and acidogenesis of FRW. Biochemical methane potential test confirmed higher methane yield (538.2mLCH4/g VSadded) from an acidogenic effluent than from raw FRW.

Seasonal monitoring of bacteria and archaea in a full-scale thermophilic anaerobic digester treating food waste-recycling wastewater: Correlations between microbial community characteristics and process variables

Microbial population size, community structure, and diversity, and the correlations of these characteristics with process variables were investigated in samples taken seasonally over two years from a full-scale thermophilic anaerobic digester treating food waste-recycling wastewater (FRW). The organic component of the FRW consisted of carbohydrate (35% of volatile solids), protein (34%) and lipid (30%). The chemical oxygen demand (COD) removal efficiency of the anaerobic digestion (AD) system negatively correlated with Na+ (2.9–7.7g/L) and lipid (3.3–22.8g/L) concentrations, which varied significantly over the two years. Tepidanaerobacter, Anaerobaculum, Defluviitoga, Keratinibaculum, Gelria, Tepidimicrobium, Caldicoprobacter, Bacillus, and Syntrophaceticus were the major bacterial genera, and Methanoculleus and Methanobacterium were the major archaeal genera. Concentrations of Na+ and lipid in the digester were negatively correlated with total bacterial and archaeal populations determined by real-time quantitative PCR. These concentrations could also significantly affect the bacterial community structure (e.g., negative correlations with Gelria), but not archaeal community structure. Lipid concentration was negatively correlated with bacterial diversity, but was not correlated with archaeal diversity. Ammonia concentration in the digester (2.0–4.3gN/L) had no significant correlation with COD removal or total bacterial/archaeal populations, but could significantly affect both bacterial and archaeal community structures, including syntrophic acetate-oxidizing bacteria and hydrogenotrophic methanogens. These results indicate that Na+, lipid and ammonia are among the key parameters that affect the process performance of a thermophilic AD system treating FRW and/or the microbial communities in it.

Characterization of food waste-recycling wastewater as biogas feedstock

A set of experiments was carried out to characterize food waste-recycling wastewater (FRW) and to investigate annual and seasonal variations in composition, which is related to the process operation in different seasons. Year-round samplings (n=31) showed that FRW contained high chemical oxygen demand (COD; 148.7±30.5g/L) with carbohydrate (15.6%), protein (19.9%), lipid (41.6%), ethanol (14.0%), and volatile fatty acids (VFAs; 4.2%) as major constituents. FRW was partly (62%) solubilized, possibly due to partial fermentation of organics including carbohydrate. Biodegradable portions of carbohydrate and protein were estimated from acidogenesis test by first-order kinetics: 72.9±4.6% and 37.7±0.3%, respectively. A maximum of 50% of the initial organics were converted to three major VFAs, which were acetate, propionate, and butyrate. The methane potential was estimated as 0.562L CH4/g VSfeed, accounting for 90.0% of the theoretical maximum estimated by elemental analysis.

Simultaneous treatment of food-waste recycling wastewater and cultivation of Tetraselmis suecica for biodiesel production.

There is an increasing interest in the use of cultivated microalgae to simultaneously produce biodiesel and remove nutrients from various wastewaters. For this purpose, Tetraselmis suecica was cultivated in flasks and fermenters using diluted food-waste recycling wastewater (FRW). The effect of FRW dilution on T. suecica growth and nutrient removal was initially tested in flasks. The maximal microalgal concentration after 14 days was in medium with a twofold dilution (28.3 × 10(6) cells/mL) and a fivefold dilution (25.5 × 10(6) cells/mL). When fivefold diluted medium was used in fermenters, the final dry cell weight of T. suecica was 2.0 g/L. The removal efficiencies of ammonium and phosphate in the fermenters were 99.0 and 52.3%, respectively. In comparison with the results of previous studies, the growth data of T. suecica in the FRW medium indicate that microalgal cultivation system incorporating removal of nutrients in FRW is feasible at the field level.

Temporal variation in methanogen communities of four different full-scale anaerobic digesters treating food waste-recycling wastewater

Methanogen communities were investigated using 454 pyrosequencing in four different full-scale anaerobic digesters treating food waste-recycling wastewater. Seasonal samples were collected for 2years, and 24 samples were available for microbial analysis from a plug flow thermophilic (PT) digester, a continuously-stirred tank thermophilic (CT) digester, an upflow anerobic sludge blanket mesophilic (UM) digester, and a continuously-stirred tank mesophilic (CM) digester. Methanoculleus, Methanobacterium, Methanothermobacter, and Methanosaeta were revealed to be key methanogens in full-scale anaerobic digestion process treating food waste-recycling wastewater. In the PT digester, Methanoculleus was dominant (96.8%). In the CT digester, Methanoculleus was dominant (95.4%) during the first year of operation, but the dominant genus was shifted to Methanothermobacter (98.5%) due to pH increase. In the UM digester, Methanosaeta was dominant (87.2%). In the CM digester, Methanoculleus was constantly dominant (74.8%) except during CM5 when Methanosaeta was dominant (62.6%) due to the low residual acetate concentration (0.1g/L).

Variations in methanogenic population structure under overloading of pre-acidified high-strength organic wastewaters

Methanogenic populations were quantitatively investigated in two separate anaerobic reactors, which received effluents from acidogenesis of either food waste-recycling wastewater or swine wastewater. Each set of the anaerobic digesters was operated under high organic loading rate (OLR) conditions (8.3–39.8 g chemical oxygen demand (COD)/L/d) with four different hydraulic retention times (10.4–3.0 days). Real-time PCR analysis demonstrated that the order Methanosarcinales was the most abundant (>55%) methanogenic group in the six runs with >50% COD removal, while the dominance (>70%) of Methanobacteriales was observed in the other two runs (<20% COD removal). Methanomicrobiales constituted a minor (<30%) population in all eight runs. The two reactors with relatively low performance were the only trials which contained less than 5 × 10 7 copies/mL of 16S rRNA gene of Methanosarcinales. These results imply that a minimum level of Methanosarcinales is important for achieving even moderate levels of process efficiency under high OLR.

A comprehensive microbial insight into two-stage anaerobic digestion of food waste-recycling wastewater

Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was achieved with the overall chemical oxygen demand (COD) removal efficiency of 73.0–85.9% at organic loading rate of up to 35.6 g COD/L·d. Performance of the acidogenic reactors, however, changed significantly during operation. This change coincided with transition of the bacterial community from one dominated by Aeriscardovia- and Lactobacillus amylovorus-related species to one dominated by Lactobacillus acetotolerans- and Lactobacillus kefiri-like organisms. In methanogenic reactors, the microbial community structures also changed at this stage along with the shift from Methanoculleus- to Methanosarcina-like organisms. This trend was confirmed by the non-metric multidimensional scaling joint plot of microbial shifts along with performance parameters. These results indicated that the overall process performance was relatively stable compared to the dynamic changes in the microbial structures and the acidogenic performance.

Growth condition and bacterial community for maximum hydrolysis of suspended organic materials in anaerobic digestion of food waste-recycling wastewater

This paper reports the effects of changing pH (5-7) and temperature (T, 40-60 degrees C) on the efficiencies of bacterial hydrolysis of suspended organic matter (SOM) in wastewater from food waste recycling (FWR) and the changes in the bacterial community responsible for this hydrolysis. Maximum hydrolysis efficiency (i.e., 50.5% reduction of volatile suspended solids) was predicted to occur at pH 5.7 and T = 44.5 degrees C. Changes in short-chain volatile organic acid profiles and in acidogenic bacterial communities were investigated under these conditions. Propionic and butyric acids concentrations increased rapidly during the first 2 days of incubation. Several band sequences consistent with Clostridium spp. were detected using denaturing gel gradient electrophoresis. Clostridium thermopalmarium and Clostridium novyi seemed to contribute to butyric acid production during the first 1.5 days of acidification of FWR wastewater, and C. thermopalmarium was a major butyric acid producer afterward. C. novyi was an important propionic acid producer. These two species appear to be important contributors to hydrolysis of SOM in the wastewater. Other acidogenic anaerobes, Aeromonas sharmana, Bacillus coagulans, and Pseudomonas plecoglossicida, were also indentified.