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This study investigates the densification/granulation of activated sludge with poor settleability, treating real industrial wastewater from a tank truck cleaning company. The wastewater is low in nutrients, acidic in nature, and high and variable in chemical oxygen demand (COD, ranging from 2770 mg·L−1 to 14,050 mg·L−1). A microbial selection strategy was applied to promote slow-growing glycogen-accumulating microorganisms (GAO) by the implementation of an anaerobic feast/aerobic famine strategy in a sequencing batch reactor (SBR). After 60 to 70 days, the uptake of carbon during the anaerobic phase exceeded 80%, the sludge morphology improved, and the sludge volume index (SVI) dropped below 50 mL·g−1. 16S rRNA gene sequencing showed the enrichment of the GAOs Defluviicoccus and Candidatus Competibacter. Stable sludge densification was maintained when using a constant organic loading rate (OLR) of 0.85 ± 0.05 gCOD·(L·d)−1, but the sludge quality deteriorated when switching to a variable OLR. In view of the integration of densified/granular sludge in a membrane bioreactor configuration, the filtration properties of the densified SBR sludge were compared to the seed sludge from the full-scale plant. The densified sludge showed a significantly lower resistance due to pore blockage and a significantly higher sustainable flux (45 vs. 15 L·(m2·h)−1). [ABSTRACT FROM AUTHOR]

This study investigates the densification/granulation of activated sludge with poor settleability, treating real industrial wastewater from a tank truck cleaning company. The wastewater is low in nutrients, acidic in nature, and high and variable in chemical oxygen demand (COD, ranging from 2770 mg·L−1 to 14,050 mg·L−1). A microbial selection strategy was applied to promote slow-growing glycogen-accumulating microorganisms (GAO) by the implementation of an anaerobic feast/aerobic famine strategy in a sequencing batch reactor (SBR). After 60 to 70 days, the uptake of carbon during the anaerobic phase exceeded 80%, the sludge morphology improved, and the sludge volume index (SVI) dropped below 50 mL·g−1. 16S rRNA gene sequencing showed the enrichment of the GAOs Defluviicoccus and Candidatus Competibacter. Stable sludge densification was maintained when using a constant organic loading rate (OLR) of 0.85 ± 0.05 gCOD·(L·d)−1, but the sludge quality deteriorated when switching to a variable OLR. In view of the integration of densified/granular sludge in a membrane bioreactor configuration, the filtration properties of the densified SBR sludge were compared to the seed sludge from the full-scale plant. The densified sludge showed a significantly lower resistance due to pore blockage and a significantly higher sustainable flux (45 vs. 15 L·(m2·h)−1).

The rapid increase in demand for renewable energy has led to a need for more efficient and effective ways to produce biogas from palm oil mill effluent (POME), which is rich in biological and chemical oxygen demand (BOD and COD). Despite its potential as a source of biogas, POME is not always effectively utilized in biogas production due to a lack of optimization of the treatment process. This study aims to address this issue by identifying the critical parameters affecting biogas production from POME and optimizing the process for maximum biogas yield and COD removal. This study employed comparative analysis and response surface methodology to optimize the performance of palm oil mill effluent (POME)-based biogas plants in Malaysia. Historical data from three commercial POME-based biogas plants in Malaysia were analyzed to identify the most critical parameters for biogas yield and COD removal. Response surface methodology, using Box–Behnken design and Design-Expert software, was then used to optimize these parameters. Sensitivity analysis was performed to interpret the impact of parameters on biogas production, with Organic Loading Rate (OLR) found to be the most critical factor for methane yield. The results showed that the optimum conditions for maximum methane production were OLR of 1.23 kg/m3·day, inlet Total Solids (TS) of 46,370 mg/L, pH of 4.5, and temperature of 45.4 °C, resulting in a 39.6% increase in methane yield (0.335 m3 CH4/kgCODremoved) and a 1.1% increase in COD removal (93.4%). [ABSTRACT FROM AUTHOR]

BACKGROUND The effects of sludge retention time, organic loading rate, specific aeration demand per membrane area (SADm) and exploiting poly(vinyl chloride)/polycarbonate/modified silver nanoparticles (PVC/PC/MAg) nanocomposite membrane in membrane fouling and removal performance of submerged membrane bioreactors (SMBRs) were compared. A reference membrane bioreactor (R‐SMBR) having a pure PVC/PC hollow fiber membrane module and no operational condition improvement was used as a reference for comparison. RESULTS: The results revealed that all of the parameters had a considerable influence on improving membrane fouling, among which optimizing SADm and installing nanocomposite membranes in the SMBRs had comparable performances. Although the nanocomposite membrane had excellent potential to boost the membrane flux up to 62% in comparison with the R‐SMBR, it did not play any noticeable roles in rectifying the removal efficiency of the SMBR. On the other hand, not only did SADm increase the membrane flux up to 55%, but it also increased about 5% of COD and 3% of NH4+‐N removal. CONCLUSIONS: Sludge characteristics were not affected by membrane modification since the concentration of extracellular polymeric substances, soluble microbial products and mean particle size were 110 ± 1 mg g−1 VSS, 54 ± 1 mg L−1 and 50 μm, respectively, for both the R‐SMBR and the SMBR in which the modified membrane was installed. However, the operational parameters could also modify the treatment performance of the SMBRs by positively impacting on sludge characteristics besides mitigating membrane fouling. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The sequential batch reactor (SBR) technology is being applied in a large number of treatment processes owing to the operational flexibility it offers. SBR's capability to carry flow equalization, biological processes, and secondary clarification within a single reactor by differing the time period of different phases and duration of aeration proves it a flexible process for wastewater treatment. In this study SBR was employed to treat the tannery industry wastewater for removing colour. The phase of the SBR was observed over a period of 50 d. Statistical based experiments were performed for optimizing the parameters viz., pH, temperature, inoculum's concentrations, agitation speed and initial concentration of the substrates on the treatment of wastewater from tanneries by the mixed culture derived from the tannery common effluent treatment plant sludge, in a batch reactor under aerobic condition. At the optimized conditions, experiments were performed by salt tolerant microorganisms such as Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Staphylococcus aureus at various organic loading rate (OLR) by varying tannery wastewater concentration and hydraulic retention time (HRT) for colour removal. A maximum decolourization 94% was obtained in SBR with the OLR 0.312 kg COD/m3 d, HRT 5 d for the substrate's initial concentration of 1,560 mg COD/L. [ABSTRACT FROM AUTHOR]

Application of anaerobic digestion (AD) has become common in treating palm oil mill effluent in Malaysia; however, employing AD in treating the organic fraction of municipal solid waste (OFMSW), especially food waste, is still scarce. This study aims to characterize the commercial Malaysian food waste (CMFW) and determine its potential as sustainable bioenergy feedstock through biogas production. The sample was digested via the biomethane potential (BMP) test with the variation of organic loading rates (OLRs), ranging from 0.38 to 3.83 gCOD/L. day, under mesophilic conditions. The digestion process was further evaluated in continuous operation using a 6-L continuous stirred-tank reactor (CSTR). The kinetic properties of the process were also determined. It was found that the CMFW had a significant amount of chemical oxygen demand of 230 g/L and an acidic pH of 4.5 with the carbon to nitrogen (C/N) ratio at 121:1. A maximum methane composition of 81% was obtained at 1.92 gCOD/L in the BMP test with specific methane production (SMP) at 0.952 L. CH4/L.COD fed. The biogas production was well-fitted with the modified Gompertz model with R2 at 0.9983 and the maximum biogas potential production rate at Rm 0.1573 L/day, whereas in the CSTR operation, a maximum methane composition of 85% was produced at OLR 6 gCOD/L. day with the SMP of 1.13 L. CH4/L.COD fed. The CSTR system was in high stability as the pH was maintained in a range of 6.6–6.7, with an alkalinity ratio of 0.28. This study indicates the CMFW is a sustainable feedstock for biogas production in Malaysia. Toward a circular economy approach, the authorities shall introduce commercial scale CMFW AD as part of managing municipal solid waste issues in Malaysia.

The objective of this investigation is to determine the effect of temperature reduction on the performance and stability of laboratory-scale up-flow anaerobic sludge blanket (UASB) treating synthetic sewage. The work was carried out using four 4-litre continuously fed UASB reactors. The operation started at a constant hydraulic retention time of ~24 hours (up flow velocity ~0.02 m hour-1) and an influent COD concentration of ~2250 mg l-1, with an organic loading rate of ~2.25 g COD l-1 day-1. During the experiment, the operating temperature was reduced in a single step from 35 to 30 ⁰C, then stepped down to 25 ⁰C. COD removal efficiency fell slightly from ~96 % in all reactors to ~93%. Effluent TSS concentrations remained below 20 mg l-1 and TSS removal efficiency ranged between 93-98%. Gas production showed a slight disturbance following the initial drop in temperature to 30 ⁰C, but stabilised at around 0.74 l CH4 l-1, 0.30 l CH4 g-1 COD added and 0.31 l CH4 g-1 COD removed. The subsequent drop to 25 ⁰C produced a stronger disturbance, but both volumetric and specific methane production recovered to the previous values by about day 412. The average biogas methane content in all reactors was unchanged or marginally higher at 78-79%.

• SuperPro and Design Expert used to optimize industrial-scale biogas production from POME. • Recirculation ratio of 148 % and HRT of 22 days yield highest methane yield. • Results offer potential for sustainable and efficient large-scale biogas production. The palm oil industry generates a considerable amount of waste, known as palm oil mill effluent (POME), which is characterized by high levels of chemical and biological oxygen demand (COD and BOD). The anaerobic digestion of POME is a potential solution for generating biogas, a renewable energy source that can be used for power generation. However, optimizing biogas production from POME is a challenging task, particularly at the industry scale due to the complex nature of the waste stream. This study aimed to improve the performance of an existing POME-based biogas plant through simulation and optimization. The POME treatment process was simulated using SuperPro Designer software. The simulated results were validated against data obtained from the existing plant, including the environmental properties of COD, BOD, total suspended solids (TSS), and total solids (TS), as well as the composition of the biogas produced. The simulation results showed good agreement with the existing plant data, although some parameters had a high relative difference due to assumptions made during the simulation. The process parameters, including the recirculation ratio and hydraulic retention time, were optimized using Design Expert software. The optimized parameters obtained were a recirculation ratio of 148 % and an HRT of 22 days, resulting in a maximum biogas flow of 859 m3/h, corresponding to a methane yield of 0.259 m3 CH 4 /kg COD removed. Confirmatory experiments were conducted over a period of 3 months using the optimized variables in the biogas plant. The results showed a high level of consistency between the predicted and experimental values with a percentage error difference ranging from 0.03 % to 2.3 %. This study's novelty lies in the integration of simulation and optimization tools to improve the performance of POME-based biogas plant. The findings of this study have significant implications for sustainable development in the palm oil industry, providing an efficient and cost-effective approach for treating POME and producing renewable energy. [ABSTRACT FROM AUTHOR]

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Abstract In this study, the efficiency of Integrated Fixed-film Activated Sludge (IFAS) system in synthetic greywater treatment and nutrients removal was studied in duration of 105 days according to different Organic Loadings Rates (OLRs). The study was operated in pilot-scale and OLRs of 0.11–1.3 gCOD/L.d. Scanning Electron Microscope (SEM) image showed that the biofilm with a proper thickness was formed on IFAS reactor’s media. The results indicated that the best removal efficiency of BOD5, COD, and TSS were 85.24, 92.52 and 90.21%, respectively, in an organic loading of 0.44 gCOD/L.d. Then, with the OLR increased, the removal efficiencies of BOD5, COD, and TSS increased as long as the organic loading reached 0.44 gCOD/L.d. But with the OLR increased more, the removal efficiency of these parameters decreased. The ANOVA statistical test results showed that the mean difference of removal efficiency in organic loadings for BOD5 (p ≤ 0.001) and COD (p = 0.003) was significant, while it was insignificant for TSS (p = 0.23). The best removal efficiencies of Total Nitrogen (TN) and Total Phosphorus (TP) were 89.60 and 86.67%, respectively, which were obtained at an OLR of 0.44 gCOD/L.d. By increasing OLR up to 0.44 gCOD/L.d, removal efficiencies of TN and TP increased, while the removal efficiency decreased with the OLR increased more, and this difference was statistically significant (p = 0.021). Finally, the results showed that the IFAS system provided a proper efficiency in treatment of the synthetic greywater and it could be used in a full scale.

The performance of a multistage passively aerated biological filter (PABF) packed with Nonwoven polyester fabric (NWPF) for municipal wastewater treatment was investigated under different operating conditions. The system was operated at different hydraulic retention times (HRTs) of 2.3, 1.72 and 1.38 h and corresponding to organic loading rates (OLRs) of 1.77, 2.15 and 2.9 kg BOD/m3. d. Increasing HRT and decreasing OLR, increased dissolved oxygen (DO) and consequently increased the removal rate of organic matters (87%), suspended solids (95.8%) and ammonia (88%). Profile results from different compartments showed that the major part of organic and suspended matters was removed in the upper layers of the system, whereas most of the suspended solids were trapped, while the nitrification process took place in the lower part of the PABF system because of the increase in DO concentrations. The results proved the advantage of using NWPF. It has pleated and rough surface which retain more biomass compared with plain surface. Excess biomass produced from PABF was negligible compared to conventional treatment systems. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of pomegranate shells was conducted in 25 L bioreactor operating at 35±0.5°C. The digester showed a reasonable amount of biogas (0.71 m³/kg VS fed) and methane (55.7%) with stable pH and acid: alkali profiles when operated at organic loading rate (OLR) from 1.0 to 3.0 kg VS/day/m-3. The reactor exhibited stable performance with methane yield of 0.44 m³/kg VS fed and reduction of 38.5% volatile solids (VS) As organic loading rate increased to 3.5 kg VS/day/m-3, accumulation of volatile fatty acid (VFA; 2797 ppm), mainly propionic acid (1617 ppm) was noticeable. The digester turned sour (pH 4.32) with lower biogas (2.5 Ld-1) and methane (30.80%) production, reflecting the case of overloading. Reversal of organic loading rate from 3.5 to 3.0 kg VS/day/m-3 gradually restored the upset anaerobic digester to normal profile in 4 weeks as judged from a gradual increase in biogas (6.5 Ld-1) and methane (58.4%). [ABSTRACT FROM AUTHOR]

The study was aimed to examine the effect of hydraulic retention time (HRT), organic loading rate (OLR) and pH, alkalinity effect on the efficiency of the production of biogas from co-digestion of food waste, azolla and sludge. The substrate was analyzed for pH, Moisture Content (%), TS (%), VS (%), VS/TS ratio (%), COD (mg/gm), Alkalinity (mg/l), VFA (mg/l), Carbon (% db), Nitrogen (% db), C/N ratio and total phosphorous (ppm or mg/gm). Anaerobic processes have been anticipated as a worthy alternative for the treatment of co-digestion of food waste with high or medium organic loads. The production of biogas through anaerobic digestion bidssignificant advantages over other biological methods of waste treatment. The purpose of study was to explain the effect of process operational parameters on the performance of an up-flow anaerobic sludge blanket reactor (UASB). The reactor was used for the co-digestion of food waste along with aquatic weed, azolla and sludge. Organic loading rate (OLR) and hydraulic retention times (HRT) were changed for effective production of biogas. The duration of study was 50 days and the temperature of the reactor was maintained at a constant 30 C while the pH was varied from 6.2 to 7.8. The result of the studyspecified an optimum OLR of 2.5–5.0 kgCOD.m-3.d-1 with COD removal efficiency of 75–96%. Similarly, the COD removal efficiency recorded for HRT 6, 12 and 18h were 88.07%, 91.97% and 87.19%, respectively. The results showed that use of azolla in co-digestion of food waste and activated sludge can improve biogas production. Thus, anaerobic treatment systems are applicable to the treatment of wastes with high levels of organics. [ABSTRACT FROM AUTHOR]

Abstract In this study, the effects of indirect voltage supply to an anaerobic digestion (AD) reactor on methane production and the removal of chemical oxygen demand (COD) were studied at different organic loading rates (OLRs) of food waste by the circulation from an auxiliary bio-electrochemical reactor (ABER) with stainless steel (STS304) electrodes. The effects of the indirect voltage on microbial communities in the AD reactor were also investigated. In a bio-electrochemical anaerobic digestion (BEAD) reactor with direct voltage, it was possible to achieve stable COD removal and methane production even at a higher OLR of 10.0 kg/(m3·d). However, in the AD reactor, the COD removal efficiency and methane production decreased sharply at an OLR of 6.0 kg/(m3·d) due to the accumulation of volatile fatty acids (VFAs) and decreases in the pH and alkalinity. The supply of indirect voltage through the ABER increased the community of exoelectrogenic bacteria and hydrogenotrophic methanogens in the AD + ABER bulk solution. As a result, rapid oxidation of the accumulated VFAs occurred, and methane production increased in the new AD + ABER system. The results confirm that an indirect voltage supply to the new AD + ABER system can have effects similar to those of a direct voltage supply to the BEAD reactor, and the findings are expected to provide useful information for the development and application of BEAD technology for commercialization. Graphical abstract Image 1 Highlights • An auxiliary bio-electrochemical reactor was studied for treating food waste. • With the auxiliary reactor, anaerobic digestion reactor performance improved. • An increase in electro-active microbial communities was seen. • Methane production and organic removal rates were stable at high organic loads. • Implications for commercialization of bio-electrochemical anaerobic digestion. [ABSTRACT FROM AUTHOR]

Abstract It has been proven that ultrasonic pretreatment (UP) has positive effect on biogas generation from previous lab-scale studies. However, that is not always the case in larger scale processes. The purpose of this study was to evaluate the effectiveness of UP to biogas generation in terms of anaerobic digestion process and energy efficiency. Parameters including total solids (TS) and ultrasonic treatment operational parameters of organic solid waste (OSW) resulted from our past lab scale UP studies were applied in this study. OSW with 6–10% TS was treated using a lab-scale ultrasonic processor using various power densities (0.2–0.6 W/mL) at different time periods up to 30 min. Results of lab scale confirmed that OSW with 6% TS sonicated with 0.2 W/mL power density in 30 min gave the best outcome for the pilot scale experiment. To simulate the condition of an actual scale, in addition to energy analysis, two different organic loading rates (OLR), namely 500 and 1500 gVS/m3day were examined. The pilot digester was fed with OSW with or without the pretreatment based on the aforementioned specifications. The results showed that UP effectively improves biogas generation in terms of quantity and quality (CH 4 /CO 2). Furthermore, it decreases the time to reach the maximum cumulative biogas volume comparing to the untreated feed. The key achievement of this research has confirmed that although the relative increase in the energy gain by the influence of UP was more remarkable under the 500 gVS/m3day OLR, energy analysis showed a better energy gain and energy benefit as well as jumping in biogas yield up to 80% for UP treated OSW under 1500 gVS/m3day OLR. [ABSTRACT FROM AUTHOR]

The organic shock loadings with varying ratios of carbon to nitrogen (C/N) caused by fluctuations of wastewater flowrate and concentration inflict a great threat on the stability of aerobic granular sludge (AGS) in practical applications. Herein, the present work proposed an enhanced shock-loading-tolerance strategy for AGS by applying a weak magnetic field (WMF). Results indicated that aerobic granules exposed in WMF kept a significant propagation regardless of the various influent organic concentrations, while those in the control reactor exhibited inadaptability with decreasing biomass concentration and bioactivity at lean substrate conditions. The enhanced extracellular polymeric substances regulating process might be one of the inducement mechanisms to cope with organic shock loadings of WMF. In addition, the AGS system in WMF showed its strong resilience in terms of the ammonia and phosphate removal. Magnetic field could inhibit the overgrowth of filamentous bacteria, and the enhanced tolerance for organic shock loadings might attribute to the enrichment of functional microbes related to structural stability such as Firmicutes and Candidatus_Competibacter. Therefore, this work revealed the enhanced mechanisms of magnetic field for improving the AGS stability towards organic shock loadings, promoting the full-scale engineering applications of both AGS and magnetization technologies in wastewater treatment. [Display omitted] • Magnetic field (MF) increased bioactivity of aerobic granular sludge (AGS) system. • AGS in MF resisted organic shock loading (OSL) with enhanced PS adjustment process. • The detrimental effects of OSL on AGS removal performance were resilient in MF. • MF enriched the functional microbes related to structural stability in AGS. • The overgrowth of filamentous bacteria could be suppressed by MF. [ABSTRACT FROM AUTHOR]

Breweries wastewater containing high concentration of organic and inorganic compounds ranks them among the top pollution generating industries. Anaerobic wastewater treatment with high organic loading rates can be achieved with lower COD strength at higher flowrates using a two–stage expanded granular sludge bed reactor. Hydraulic retention time (HRT), pH, temperature, and COD strength were varied for process optimization. Brewery wastewater with 20, 30, and 40 g COD/L as a substrate for two temperature ranges were evaluated. Under mesophilic conditions (36 °C), results show COD removal efficiency (R%) and biogas production rate increased by 6% and 40% respectively as HRTs increased, maintaining a constant OLR. Results imply for equivalent OLRs, better reactor performance is achieved when running high concentration COD at slower rate compared with a lower concentration at higher rate. This implies diffusion limitation where complex proteins and fats are passed through the reactor faster than their metabolism rate in the digester. Under thermophilic conditions (50 °C), results show COD removal efficiency (R%) and biogas production rate increased by 4% and 40% respectively as the HRTs increased, while maintaining a constant OLR. This implies the higher and stronger population of anaerobes are present under thermophilic condition rather than mesophilic condition. [ABSTRACT FROM AUTHOR]

This study focuses on the effects of organic loading rate (OLR) on the removal of N , N -Dimethylformamide(DMF), m-Cresol (MC) and isopropyl alcohol (IPA) by a pilot-scale anaerobic membrane bioreactor (AnMBR) for treating chemical synthesis-based antibiotic solvent wastewater at period of improved influent COD concentration with decreased HRT. The whole process was divided into five stages in terms of the variation of OLR ranging from 3.9 to 12.7 kg COD/(m 3 ·d). During 249 days of operating time, the average DMF, MC, IPA removal efficiency were 96.9%,98.2% and 96.4%, respectively. Cake layer was accumulated on the membrane surface acted as a dynamic secondary biofilm which lead to the increase of physical removal rate. In addition, mathematical statistical models was built on the linear regression techniques for exploring the inner relationship between EPS and the performance of the AnMBR. [ABSTRACT FROM AUTHOR]

In this study, the efficiency of Integrated Fixed-film Activated Sludge (IFAS) system in synthetic greywater treatment and nutrients removal was studied in duration of 105 days according to different Organic Loadings Rates (OLRs). The study was operated in pilot-scale and OLRs of 0.11-1.3 gCOD/L.d. Scanning Electron Microscope (SEM) image showed that the biofilm with a proper thickness was formed on IFAS reactor's media. The results indicated that the best removal efficiency of BOD, COD, and TSS were 85.24, 92.52 and 90.21%, respectively, in an organic loading of 0.44 gCOD/L.d. Then, with the OLR increased, the removal efficiencies of BOD, COD, and TSS increased as long as the organic loading reached 0.44 gCOD/L.d. But with the OLR increased more, the removal efficiency of these parameters decreased. The ANOVA statistical test results showed that the mean difference of removal efficiency in organic loadings for BOD (p ≤ 0.001) and COD (p = 0.003) was significant, while it was insignificant for TSS (p = 0.23). The best removal efficiencies of Total Nitrogen (TN) and Total Phosphorus (TP) were 89.60 and 86.67%, respectively, which were obtained at an OLR of 0.44 gCOD/L.d. By increasing OLR up to 0.44 gCOD/L.d, removal efficiencies of TN and TP increased, while the removal efficiency decreased with the OLR increased more, and this difference was statistically significant (p = 0.021). Finally, the results showed that the IFAS system provided a proper efficiency in treatment of the synthetic greywater and it could be used in a full scale. [ABSTRACT FROM AUTHOR]

• Δ G sw a can normalize the stability of AGS. • Microbial and chemical properties were more important for Δ G sw a than physical ones. • Reasonable increase in OLR or HSF reduced Δ G sw a and enhanced stability of AGS. The stability of aerobic granular sludge (AGS) has been evaluated by lots of physicochemical and microbial characteristic indicators, but none of them could singly and comprehensively characterize the stability of AGS. Gibbs free energy change (∆G) could reflect the stable state of the whole system by the second law of thermodynamics, so ∆G of the sludge-water interface ( Δ G sw a) was proposed to characterize the stability of AGS in this study. Organic loading rate (OLR) and hydraulic shear force (HSF) as the primary external energy inputs were selected at different levels in four reactors. Results showed that a reasonable increase in OLR or HSF could reduce Δ G sw a , and its influence on Δ G sw a had two paths: affecting the surface roughness of sludge directly (Path 1); on the other hand, EPS producers like denitrifiers were enriched, promoting the secretion of PN such as tryptophan and protein-like to affect Δ G sw a (Path 2). These indicators were correlated with Δ G sw a significantly, especially genus Paracoccus spp. (class Alphaproteobacteria) (-0.74, p <0.001) and Amide III (-0.81, p <0.001), indicating that Path 2 had a more significant influence on Δ G sw a. In addition, the absolute values of correlation between physical stability indicators and Δ G sw a were around 0.80 (p <0.001). Therefore, Δ G sw a can be normalized to characterize the stability of AGS. This study establishes Δ G sw a as the normalized indicator for the stability of AGS, which provides specific theoretical guidance for operating parameter regulation in engineering application. [Display omitted] [ABSTRACT FROM AUTHOR]

Salt-tolerant aerobic granular sludge (SAGS) technology has shown potentials in the treatment of ultra-hypersaline high-strength organic wastewater. However, the long granulation period and salt-tolerance acclimation period are still bottlenecks that hinder SAGS applications. In this study, "one-step" development strategy was used to try to directly cultivate SAGS under 9% salinity, and the fastest cultivation process was obtained under such high salinity compared to the previous papers with the inoculum of municipal activated sludge without bioaugmentation. Briefly, the inoculated municipal activated sludge was almost discharged on Day 1–10, then fungal pellets appeared and it gradually transitioned to mature SAGS (particle size of ∼4156 μm and SVI 30 of 57.8 mL/g) from Day 11 to Day 47 without fragmentation. Metagenomic revealed that fungus Fusarium played key roles in the transition process probably because it functioned as structural backbone. RRNPP and AHL-mediated systems might be the main QS regulation systems of bacteria. TOC and NH 4 +-N removal efficiencies maintained at ∼93.9% (after Day 11) and ∼68.5% (after Day 33), respectively. Subsequently, the influent organic loading rate (OLR) was stepwise increased from 1.8 to 11.7 kg COD/m3·d. It was found that SAGS could maintain intact structure and low SVI 30 (< 55 mL/g) under 9% salinity and the OLR of 1.8–9.9 kg COD/m3·d with adjustment of air velocity. TOC and NH 4 +-N (TN) removal efficiencies could maintain at ∼95.4% (below OLR of 8.1 kg COD/m3·d) and ∼84.1% (below nitrogen loading rate of 0.40 kg N/m3·d) in ultra-hypersaline environment. Halomonas dominated the SAGS under 9% salinity and varied OLR. This study confirmed the feasibility of direct aerobic granulation in ultra-hypersaline environment and verified the upper OLR boundary of SAGS in ultra-hypersaline high-strength organic wastewater treatment. [Display omitted] • SAGS could be directly cultivated under 9% salinity in 47 days using municipal AS. • Fungal pellets functioned as backbone and successfully transitioned to SAGS. • Fungus Penicillium and Fusarium contributed to the initialization of SAGS. • High TOC & TN removal ratios were obtained below 8.1 kg COD/m3·d under 9% salinity. • Increased air velocity could help maintain stability of SAGS under high OLR. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a biological process that can be used for food waste and leachate treatment. A semi- continuous anaerobic digestion experiment was carried out treating a synthetic feedstock made of 50% synthetic food waste and 50% leachate. The total solids concentration inside the reaction was maintain constant and different TS were investigated varying from 5 to 7% TS. The aim of this study was to investigate the effect pH and Oxidation Reduction Potential (ORP) on the biogas production at the different organic loading rate tested. These operational parameters were used to predict and control a mesophilic screw digester. The results of this study indicated that the optimum of ORP and pH during the acidogenesis phase were -284 ± 32.71 mV and 5.76 ± 0.24, respectively. The optimum of ORP and pH during the methanogenesis phase were -335.63 ± 28.97 mV and 7.49 ± 0.24, respectively. The highest biogas and CH4 content were obtained for the OLR equal to 5%TS condition. The value of biogas and CH4 content were0.29 L biogas/g COD utilized and 68% of methane content, respectively. [ABSTRACT FROM AUTHOR]

A quorum quenching (QQ) consortium comprised of both acyl homoserine lactones (AHLs)- and autoinducer-2 (AI-2)-degrading bacteria, either immobilized in polymer-coated alginate beads or in liquid suspension, was examined for fouling control in lab-scale MBRs under both steady and changing organic loading rates (OLRs). Under steady conditions the QQ consortium retarded biofouling by a factor of 3. However, a continuous increase in OLR vastly reduced the effectiveness of QQ bacteria; the biofouling was retarded only by factors of 1.4–1.8. A significant increase in extracellular polymeric substance (EPS), especially loosely-bound EPS in mixed liquor together with an increase in polysaccharide content up to 4 times in EPS resulted from the increase in OLR, was attributed to the impaired QQ efficacy. In control MBRs, cake layer resistance was the major factor (>60%) contributing to the increased trans-membrane pressure, as compared with pore blockage resistance and intrinsic membrane resistance. In contrast, the pore blockage resistance became dominant in QQ MBRs (>40%). [ABSTRACT FROM AUTHOR]

In this study, performance of Integrated Fixed-film Activated Sludge (IFAS) system in treatment of Linear Alkylbenzene Sulfonate (LAS), and oil & grease in synthetic greywater and effect of Organic Loading Rates (OLRs) on removal efficiency within a period of 105 days were investigated. Present study was carried out in a pilot scale under such conditions as temperature of 30 ± 1 °C, dissolved oxygen of 2.32 ± 0.91 mg/l, pH of 8.01 ± 0.95 and OLRs of 0.11–1.3gCOD/L.d. Also, Scanning Electron Microscopy (SEM) images were employed to specify rate of the biofilm formed on the media inside the reactor IFAS. The best removal efficiency for COD, LAS and oil and grease were respectively obtained as 92.52%, 94.24% and 90.07% in OLR 0.44gCOD/L.d. The assessment of loading rate indicated that with increased OLR to 0.44gCOD/L.d, removal efficiency of COD, oil and grease was increased while with increased OLR, removal efficiency was decreased. In doing so, based on the statistical test ANOVA, such a difference between removal efficiencies in diverse OLRs was significant for COD (p = 0.003), oil and grease (p = 0.01). However, in terms of LAS, with increased value of OLR to 0.44gCOD/L.d, the removal efficiency was increased and then with higher OLRs, removal efficiency was slightly decreased that is insignificant (p = 0.35) based on the statistical test ANOVA. The SEM images also showed that the biofilm formed on the media inside IFAS reactor plays a considerable role in adsorption and biodegradation of LAS, and oil & grease in greywater. The linear relation between inlet COD values and rate of removed LAS indicated that the ratio of inlet COD (mg/L) to removed LAS (mg/L) was 0.4. Therefore, use of IFAS system for biodegradation of LAS, oil and grease in greywater can be an applicable option. [ABSTRACT FROM AUTHOR]

Integrated aerobic granules were first cultivated in two sequencing batch reactors (SBRs) (A1 and A2). Then, A1's influent organic loading rate (OLR) was changed from alternating to constant (cycling time was still 6 h), while A2's cycling time varied from 6 to 4 h (influent OLR strategy remained alternating). After 30-day operation since the manipulative alternations, granule breakage happened in two reactors at different operational stages, along with the decrease of granule intensity. Granule diameter in A1 declined from the original 0.84 to 0.32 cm during the whole operation, while granules in A2 dwindled to 0.31 cm on day 22 with similar size to A1. Both the amount of total extracellular polymeric substances (EPSs) and the protein were declining throughout the operation, and the large molecular weight of protein was considered closely related to the stability of aerobic granules. The relative AI-2 level decreased at the same time, and influent OLR strategy might had more evident impact on quorum sensing (QS) ability of sludge compared with starvation period. Combined with microbial results, the decline of total EPS amount in two reactors could be concluded as follows: During the reactor operation, some functional bacteria gradually lost their dominance and were eliminated from the reactors, which finally caused granule disintegration. In summary, the results further confirmed that alternating OLR and proper starvation period were two major factors in effective cultivation and stability of aerobic granules from the perspective of QS. [ABSTRACT FROM AUTHOR]

Biogas plants are the most complex systems and are heavily studied in the field of renewable energy. A biogas system is mainly influenced by biological and technical parameters that strongly interact with each other. One recommended practice when operating a biogas plant is the recirculation of the substrate from the second fermenter into the first fermenter, which extends the recirculation amount (RA) and, in turn, the recirculation rate (RR). This technique should be applied to support and secure the biogas process. In this investigation, the RA was varied, starting with the recommended "best practice" of 10.0 m3/d (RR 40%). Every ten days, the RA was reduced in steps of 1.5 m3/d, with 5.5 m3/d (RR 27%) being the final value. The basic question to be addressed concerns to what extent the RR influences the methane yield and thereby influence the efficiency of a manure-based biogas plant in practice. Diverting the "best practice" to a RR of 27% stabilised the fermentation process and lead to significantly higher methane yields with smaller standard deviations. In addition, with a reduced RR, the standard optimal acid concentration within the biogas substrate was approximately reached. [ABSTRACT FROM AUTHOR]

In the 21st century, people migrated from rural to urban areas for several reasons. As a result, the populations of Indian cities are increasing day by day. On one hand, the country is developing in the field of science and technology and on the other hand, it is encountering a serious problem called ‘Environmental degradation’. Due to increase in population, the generation of solid waste is also increased and is being disposed in open dumps and landfills which lead to air and land pollution. This study is attempted to generate energy out of organic solid waste by the bio- fermentation process. The study was conducted for a period of 7 months at Erode, Tamilnadu and the reading on various parameters like Hydraulic retention time, organic loading rate, sludge loading rate, influent pH, effluent pH, inlet volatile acids, out let volatile fatty acids, inlet VSS/TS ratio, outlet VSS/TS ratio, influent COD, effluent COD and % of COD removal are recorded for every 10 days. The aim of the present study is to develop a model through multiple linear regression analysis with COD as dependent variable and various parameters like HRT, OLR, SLR, influent, effluent, VSS/TS ratio, influent COD, effluent COD, etc as independent variables and to analyze the impact of these parameters on COD. The results of the model developed through step-wise regression method revealed that only four parameters Influent COD, effluent COD, VSS/TS and Influent/pH were main influencers of COD removal. The parameters influent COD and VSS/TS have positive impact on COD removal and the parameters effluent COD and Influent/pH have negative impact. The parameter Influent COD has the highest order of impact, followed by effluent COD, VSS/TS and influent pH. The other parameters HRT, OLR, SLR, INLET VFA and OUTLET VFA were not significantly contributing to the removal of COD. The implementation of the process suggested through this study might bring in dual benefit to the community, viz treatment of solid waste and creation of energy. [ABSTRACT FROM AUTHOR]

It is a common sense that high organic loading rate (OLR) leads to the faster formation of aerobic granular sludge (AGS), while the effects of increased OLR on the direct development of salt-tolerant aerobic granular sludge (SAGS) in hypersaline wastewater is still unknown. In this study, four identical sequencing batch reactors (SBRs) were directly fed with 3% salinity wastewater and operated at different OLRs to cultivate SAGS. Granules firstly appeared on Day 10, 7, 5, and 8, and dominated on Day 23, 16, 10, and 13 in four SBRs operated under OLR of 2.4, 3.6, 4.8, and 7.2 kg COD/m3·d, respectively. The former three granules matured on Day 29 (D50 of 550 µm), 25 (D50 of 639 µm), and 25 (D50 of 808 µm), respectively, while the loose and fluffy filamentous granules cultivated under the highest OLR failed to reach the traditional criterion of AGS. Overall, increased OLR could accelerate the formation of AGS that had larger sizes and lower microbial diversities. However, unlike salt-free wastewater, the appropriate OLR for rapid formation of compact AGS in hypersaline wastewater was only 3.6 kg COD/m3·d, since the higher OLRs with higher hydraulic selection pressure led to the massive sludge loss and the formation of instable fluffy granules during granulation period. Bacterial community analysis revealed Corynebacterium , Marinobacterium , Paracoccus , Halomonas , and Vibrio were the main genera in four SBRs, in which Corynebacterium had certain abundance at all OLRs, and Vibrio and Paracoccus favored low OLR, while Halomonas and Marinobacterium dominated the SBRs with high OLRs. This study contributed to a better understanding of SAGS granulation under different OLR conditions in hypersaline wastewater. [Display omitted] • Granulation at different OLRs in hypersaline wastewater was first studied. • Larger granules with lower microbial diversities formed at higher OLR. • High OLR led to massive sludge loss and formation of instable filamentous granules. • The appropriate OLR for rapid SAGS formation was 3.6 kg COD/m3·d. • Paracoccus favored low OLR, while Halomonas and Marinobacterium were opposite. [ABSTRACT FROM AUTHOR]

The effects of pH, temperature and high organic loading rate (OLR) on lactic acid production from food waste without extra inoculum addition were investigated in this study. Using batch experiments, the results showed that although the hydrolysis rate increased with pH adjustment, the lactic acid concentration and productivity were highest at pH 6. High temperatures were suitable for solubilization but seriously restricted the acidification processes. The highest lactic acid yield (0.46 g/g-TS) and productivity (278.1 mg/L h) were obtained at 37 °C and pH 6. In addition, the lactic acid concentration gradually increased with the increase in OLR, and the semi-continuous reactor could be stably operated at an OLR of 18 g-TS/L d. However, system instability, low lactic acid yield and a decrease in VS removal were noticed at high OLRs (22 g-TS/L d). The concentrations of volatile fatty acids (VFAs) in the fermentation mixture were relatively low but slightly increased with OLR, and acetate was the predominant VFA component. Using high-throughput pyrosequencing, Lactobacillus from the raw food waste was found to selectively accumulate and become dominant in the semi-continuous reactor. [ABSTRACT FROM AUTHOR]

Biogas plants are the most complex systems and are heavily studied in the field of renewable energy. A biogas system is mainly influenced by biological and technical parameters that strongly interact with each other. One recommended practice when operating a biogas plant is the recirculation of the substrate from the second fermenter into the first fermenter, which extends the recirculation amount (RA) and, in turn, the recirculation rate (RR). This technique should be applied to support and secure the biogas process. In this investigation, the RA was varied, starting with the recommended “best practice” of 10.0 m3/d (RR 40%). Every ten days, the RA was reduced in steps of 1.5 m3/d, with 5.5 m3/d (RR 27%) being the final value. The basic question to be addressed concerns to what extent the RR influences the methane yield and thereby influence the efficiency of a manure-based biogas plant in practice. Diverting the “best practice” to a RR of 27% stabilised the fermentation process and lead to significantly higher methane yields with smaller standard deviations. In addition, with a reduced RR, the standard optimal acid concentration within the biogas substrate was approximately reached.

Enzymatically hydrolyzed brewer’s spent grain (BSG) was digested in two expanded granular sludge beds (EGSBs, named BSG1 and BSG2, respectively). Both reactors were operated with the same organic loading rate (OLR) from 1 to 10 kg COD m −3 d −1 during the first 45 days. Hereafter a rapid OLR increase was applied to BSG2 from 10 to 16 kg COD m −3 d −1 within three weeks, while the OLR of BSG1 was increased by less than 2 kg COD m −3 d −1 in the same period. Results showed that a 30% decrease in COD removal and 70% decrease in methane yield appeared in BSG2 after the rapid OLR increase, and volatile fatty acid (VFA) accumulated more than thirty times compared to BSG1. The biomass structure deteriorated and 15% of the biomass was lost from the BSG2 reactor. 454-PyroTag and qPCR analysis revealed a rapid growth of acidifiers (i.e., Bacteroides ) and a unique microbial community in BSG2 following the rapid increase in OLR. [ABSTRACT FROM AUTHOR]

Pharmaceuticals constitute a well-known group of emerging contaminants with an increasing significance in water pollution. This study focuses on three pharmaceuticals extensively used in Finland and which can be found in environmental waters: ibuprofen, diclofenac and carbamazepine. Biodegradation experiments were conducted in a full-scale Wastewater Treatment Plant (WWTP) and in laboratory-scale Sequencing Batch Reactors (SBRs). The SBRs were operated at 12 °C, with a sludge retention time (SRT) 10–12 d and organic loading rates (OLRs) of 0.17, 0.27 and 0.33 kg BOD 7 m - 3 d - 1 . Ibuprofen was found to biodegrade up to 99%. The biodegradation rate constants ( k biol ) for ibuprofen were calculated for full-scale and laboratory processes as well as under different laboratory conditions and found to differ from 0.9 up to 5.0 l g SS − 1 d − 1 . Diclofenac demonstrated an unexpected immediate drop of concentration in three SBRs and partial recovery of the initial concentration in one of the reactors. High fluctuating in diclofenac concentration was presumably caused by removal of this compound under different concentrations of nitrites during development of nitrifying activated sludge. Carbamazepine showed no biodegradation in all the experiments. [ABSTRACT FROM AUTHOR]

The effect of an organic loading rate (OLR) and a hydraulic retention time (HRT) was evaluated by comparing the single-stage and two-stage anaerobic digestion processes. Wastes from the food processing industry (FPW) and the organic fraction of the municipal solid waste (OFMSW) were used as substrates. The OLR was increased at each step from 2 gVS/l/d to 14 gVS/l/d, and the HRT was decreased from 10 days to 3 days. The highest theoretical methane yield achieved in the single-stage process was about 84% for the FPW during an OLR of 3 gVS/l/d at a HRT of 7 days and 67% for the OFMSW at an OLR of 2 gVS/l/d and a HRT of 10 days. The single-stage process could not handle a further increase in the OLR and a decrease in the HRT; thus, the process was stopped. A more stable operation was observed at higher OLRs and lower HRTs in the two-stage system. The OLR could be increased to 8 gVS/l/d for the FPW and to 12 gVS/l/d for the OFMSW, operating at a HRT of 3 days. The results show a conclusion of 26% and 65% less reactor volume for the two-stage process compared to the single-stage process for the FPW and the OFMSW, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Anaerobic digestion is a commercial reality for several kinds of waste. Nonetheless, anaerobic digestion of single substrates presents some drawbacks linked to substrate characteristics. Anaerobic co-digestion, the simultaneous digestion of two or more substrates, is a feasible option to overcome the drawbacks of mono-digestion and to improve plant׳s economic feasibility. At present, since 50% of the publication has been published in the last two years, anaerobic co-digestion can be considered the most relevant topic within anaerobic digestion research. The aim of this paper is to present a review of the achievements and perspectives of anaerobic co-digestion within the period 2010–2013, which represents a continuation of the previous review made by the authors [3]. In the present review, the publications have been classified as for the main substrate, i.e., animal manures, sewage sludge and biowaste. Animal manures stand as the most reported substrate, agro-industrial waste and the organic fraction of the municipal solid waste being the most reported co-substrate. Special emphasis has been made to the effect of the co-digestion over digestate quality, since land application seems to be the best option for digestate recycling. Traditionally, anaerobic co-digestion between sewage sludge and the organic fraction of the municipal solid waste has been the most reported co-digestion mixture. However, between 2010 and 2013 the publications dealing with fats, oils and greases and algae as sludge co-substrate have increased. This is because both co-substrates can be obtained at the same wastewater treatment plant. In contrast, biowaste as a main substrate has not been as studied as manures or sewage sludge. Finally, three interdisciplinary sections have been written for addressing novelty aspects in anaerobic co-digestion, i.e., pre-treatments, microbial dynamics and modeling. However, much effort needs to be done in these later aspects to better understand and predict anaerobic co-digestion. [Copyright &y& Elsevier]

Highlights: [•] Uncertainties affecting profitability of biogas from OMSW was evaluated. [•] Collection and transportation costs affect the profitability. [•] The bigger the plant, the more energy and economic efficient it is. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biohydrogen from glucose in an up-flow anaerobic packed bed reactor was studied. [•] Design modification were made in the settling zone to capture the detached biomass. [•] Impact of organic loading rate on hydrogen yield were assessed. [•] Maximum hydrogen yield of 2.1mol-H2 mol−1-glucose was achieved. [•] The biomass yield in the modified system was lower than the conventional system. [Copyright &y& Elsevier]

Highlights: [•] Pretreating organic solid wastes leads to an enhanced anaerobic digestion process. [•] Pretreatments may also reduce the cost for post treatment of digestates. [•] Efficiency of pretreatment methods depends on the substrates’ characteristics. [•] Only few pretreatment methods are successfully applied at full-scale to date. [ABSTRACT FROM AUTHOR]

This laboratory-scale study investigated the performance of a low-cost anaerobic digester for microalgae. Low (∼2%) solids content wastewater-grown microalgal biomass (MB) was digested in an unmixed, accumulating-volume reactor (AVR) with solid and liquid separation that enabled a long solids retention time. AVRs (2 or 20 L) were operated at 20 °C, 37 °C or ambient temperature (8–21 °C), and the influence of two pretreatments – low-temperature thermal (50–57 °C) and freeze-thaw – on algal digestion were studied. The highest methane yield from untreated MB was in the 37 °C AVR with 225 L CH4 kg volatile solids (VS)−1, compared with 180 L CH4 kg VS−1 added in a conventional, 37 °C completely stirred tank reactor (CSTR), and 101 L CH4 kg VS−1 added in the 20 °C AVR. Freeze-thaw and low-temperature thermal pretreatments promoted protein hydrolysis and increased methane yields by 32–50% at 20 °C, compared with untreated MB. Pretreatments also increased the mineralisation of nitrogen (41–57%) and phosphorus (76–84%) during digestion. MB digestion at ambient temperature was comparable with digestion at 20 °C, until temperature dropped below 16 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Full-scale modification of anaerobic digestion parameters to investigate foaming causes. [•] The suspected contributors to anaerobic digester foaming were present in all 3 cases. [•] No foaming occurred because primary foaming cause was absent. [•] Reduced mixing to abate foaming did not affect homogeneity in digesters. [ABSTRACT FROM AUTHOR]

Highlights: [•] Palm oil wastewater is treated in suspended closed anaerobic reactor. [•] Significant reduction of chemical oxygen demand was obtained. [•] Accumulated high level of volatile fatty acids could affect methane composition. [•] High methane production rate was obtained from palm oil wastewater. [ABSTRACT FROM AUTHOR]

Highlights: [•] Organic loading rate was increased by factor 3 within 6weeks. [•] Stable process was accomplished to an organic loading rate up to 9.5kgVSm−3 d−1. [•] The risk of process failures was minimized by addition of calcium oxide. [•] Aggregate formation stabilized the biogas production process. [•] Methane yield >80% despite hydrogen partial pressure of >0.1mbar in gaseous phase. [Copyright &y& Elsevier]

Abstract: A pilot scale aerobic submerged membrane bioreactor (MBR) for treating cosmetic wastewater was operated for 205 days. During the operation, increasing organic loading rates (OLR) were applied in the MBR. The effects of the applied OLR (from 0.25 to 2 g COD l-1 d-1) were evaluated regarding chemical oxygen demand (COD) and anionic surfactant (AS) removal efficiencies. At an optimal volumetric OLR of 1.52 g COD l-1 d-1, the MBR achieved the highest COD and AS removal efficiencies (83.73% and 98.13%, respectively). The influence of the OLR on filtration performance was assessed, including GC/MS analysis of raw and treated wastewater. The denaturing gradient gel electrophoresis (DGGE) analysis was used to monitor the dynamics of the bacterial communities inside the bioreactor. Major bands of DGGE patterns of sludge samples were further sequenced. Phylogenetic analysis indicated that the majority of the sequences obtained were affiliated with α-Proteobacteria, Actinobacteria and Fimicutes. [Copyright &y& Elsevier]

Highlights: [•] Co-digestion of CM and CS were investigated under batch and continuous conditions. [•] CSTR showed stable methane yield of 223±7mL/gVSadded at OLR of 4gVS/L/d. [•] Post-digestion of digestate gave extra energy yield up to 2.6MJ/kgVSadded. [•] Pyrolysis of digestate could produce valuable pyrolysis gas with LCV of 10.9MJ/m3. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of biohydrogen production from sucrose, slurry-type piggery waste and food waste under the effects of the reactor configurations and operational pHs (6 and 9) were examined by using heat-treated anaerobic sludge as a seed biomass. When sucrose was used in the batch test, the maximum hydrogen yield was 0.12–0.13 g COD (as H2)/g COD (1.41–1.43 mol/mol hexose) at pH 6. In contrast, 0.10–0.11 g COD (as H2)/g COD (1.12–1.21 mol/mol hexose) hydrogen yield was achieved from the reactor at pH 9. On the other hand, hydrogen production was not observed in the continuous sequencing batch mode fermenters fed with sucrose. Profile analysis at each cycle revealed hydrogen production at the initial operation periods but eventually only methane at 36 days. When slurry-type piggery waste was used as the substrate, the upflow elutriation-type fermenters produced methane but not hydrogen after 30 days operation. The fermentation intermediate profile showed that the hydrogen produced might have been consumed by homoacetogenic or propionate producing reactions, and eventually converted into methane by acetoclastic methanogens. The downflow leaching bed fermenters using food waste produced 0.013 L H2/g volatile solids (VS) (0.0061 g COD (as H2)/g COD) at pH 6 with 54% VS reduction whereas 0.0041 L H2/g VS (0.0020 g COD (as H2)/g COD) was produced at pH 9 with 86% VS reduction. The results show that the hydrogen produced should be released rapidly from the reactor before it can be consumed in other biochemical reactions, and substrates with high pH level (>9.0) can be used directly to produce hydrogen without needing to adjust the pH. [Copyright &y& Elsevier]

Highlights: [•] In-house upscale of Automatic Methane Potential Test System to 5L was developed. [•] Full-scale inocula, substrates and organic loading were used in tests. [•] Tests were characterized by short preparation times, accuracy and high-through put. [•] Same scales, equipment and methodologies were used in batch and continuous tests. [•] Increased full-scale decision making value of the developed approach was shown. [Copyright &y& Elsevier]

Abstract: Biodiesel has become one of the most attractive fuels since it was globally understood the renewability of its nature. Glycerol is a major byproduct of biodiesel production which is often regarded as a waste stream which is accompanied by a significant disposal cost. The effect of glycerol on the performance of a cascade of two anaerobic continuous stirred tank (CSTR) reactors treating thickened sludge at mesophilic conditions was investigated. The objective of this study was to evaluate the use of glycerol as a co-substrate during the anaerobic treatment of sewage sludge. For this purpose, feed mixtures of sewage sludge supplemented with 0%, 2%, 3% and 4% (v/v) glycerol were tested at hydraulic retention times between 12.3 d and 19.7 d. By adding 4% of glycerol, the system failed due to overloading. In all other cases, biodegradability of mixtures estimated to be higher than 88%, while the methane yield coefficient was 0.8 Lbiogas/g TVSremoved. Moreover, co-digestion improved biogas production by 3.8–4.7 times. [Copyright &y& Elsevier]