Search

Two anaerobic membrane bioreactors (AnMBRs) equipped with different membrane pore size (0.4 or 0.05 µm) were operated at 25˚C and fed with domestic wastewater. The hydraulic retention time (HRT) of the reactors was shortened. The microbial communities of the two AnMBRs were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT. The predominant Archaea was an aceticlastic methanogen Methanosaeta. The composition of hydrogenotrophic methanogens changed with the HRTs: the population of Methanobacterium was higher for longer HRTs, whereas the population of unclassified Methanoregulaceae was higher for shorter HRTs. The Anaerolineae, Bacteroidia and Clostridia bacteria were dominant in both of the reactors, with a combined relative abundance of over 55%. The relative abundance of Anaerolineae was proportional to the biogas production performance. The change in the population of hydrogenotrophic methanogens or Anaerolineae can be used as an indicator for process monitoring. The sum of the relative abundance of Anaerolineae and Clostridia fluctuated slightly with changes in the HRT in both AnMBRs when the reactor was stably operated. The co-occurrence analysis revealed the relative abundance of the operational taxonomic units belonging to Anaerolineae and Clostridia was functionally equivalent during the treatment of real domestic sewage. A principal coordination analysis revealed that the changes in the microbial community in each reactor were consistent with the change of HRT. In addition, both the HRT and the stability of the process are important factors for maintaining microbial community structures.

The water body inside the constructed wetland is affected by various factors, and the flow state is relatively complicated. There will always be a certain degree of low velocity area and rapid outflow phenomenon, which makes part of the space in the wetland unable to be effectively used. Based on Computational Fluid Dynamics (CFD) technology, this paper uses Fluent's porous media model and discrete phase model to establish a hydrodynamic model of up and down baffled subsurface flow constructed wetland system. The internal flow field of the wetland is simulated, and the hydraulic performance of different baffle settings and substrate laying methods in the wetland is systematically evaluated. The results show that when the number of baffles is the same, the hydraulic efficiency is higher when the first baffle is located on the lower part of the substrate. Compared with the position of the baffle, the increase in the number of baffles does not significantly improve the hydraulic efficiency of the constructed wetland. The substrate layer thickness ratio has a significant effect on the two parameters of the variance of the hydraulic residence time distribution (σ2) and the flow divergence (σ02). By increasing the thickness of the middle substrate, the low flow rate phenomenon caused by the small porosity substrate area of the upper layer and the rapid outflow phenomenon of the lower substrate can be improved to a certain extent, the utilization efficiency of the middle substrate layer is improved, and the hydraulic performance is increased. The research results are of great significance for improving the utilization of wetland space and ensuring its efficient decontamination and purification function. HIGHLIGHTS The hydraulic performance of constructed wetland is affected by baffle setting and substrate laying.; The first baffle is located at the lower part of the substrate with higher hydraulic efficiency.; The layer thickness ratio of the substrate mainly affects the hydraulic residence time distribution and the flow divergence.

In extent of this study, ammonium removal from wastewater through biological nitrification process was performed in upflow biofilm reactors. The effects of hydraulic retention time (HRT) and nitrogen loading rate (NLR) on the nitrification process were investigated. For the nitrification process, the optimum HRT and NLR were determined to be 80 hr and 0.044 kg/ m3.day, respectively. It is observed that the efficiency increased from 53% to 96% along with the increase in HRT from 22 hr to 80 hr and the decrease in NLR from 0.165 kg/m3.day to 0.044 kg/m3.day.The substrate consumption kinetics were studied in the attached growth reactor, and the Monod kinetic model, first-order kinetic model, modified Stover-Kincannon and Grau second-order kinetic models were examined. For the substrate consumption kinetic study, experimental studies were performed at 125, 150, 175, 200, 225 mg NH4-N/L substrate concentrations and 62 hr at HRT during the nitrification process. As a result of the considering kinetic studies, it was determined that the kinetic study was suitable for the modified Stover- Kincannon kinetic model that had the highest coefficient of regression by 0.997 and when the effluent NH4-N concentrations and NH4-N removal efficiencies calculated using kinetic models were examined, it was observed that the results closest to the experimental results (4.5, 10.1, 19.7, 26.2 and 42.3 mg NH4-N/L) were obtained through the modified Stover-Kincannon model (4.16, 10.71, 18.92, 28.12 and 39.51 mg NH4-N/L)., This study was supported by Cumhuriyet University Scientific Research Projects (CÜBAP) Commission within the scope of project M-494.

The objective of the current work is to study the impact of the operational parameters' variation (HRT, OLR and T) on biomethane productivity in a periodic anaerobic baffled reactor (PABR). The feedstock used was a biomass product named food residue biomass (FORBI), which is dried and shredded source-separated household food waste. The PABR is an innovative, high-rate bioreactor. Apart from the hydraulic retention time (HRT) and the organic loading rate (OLR), an important operational parameter is the switching period (T) of the feeding compartment: when T is high, the bioreactor operation is similar to an anaerobic baffled reactor (ABR), while when it is low, the operation approaches that of an upflow anaerobic sludge blanket reactor (UASBR). Nine distinct experimental phases were conducted, during which the operational parameters of the PABR were consecutively modified: the HRT varied from 9 to 2.5 days, T between 2 days and 1 and finally the OLR from 1.24 gCOD/Lbioreactor*d to 8.08 gCOD/Lbioreactor*d. The maximum biomethane yield was 384 LCH4/kgFORBI corresponding to the operation at HRT = 5 d, OLR = 2.14 gCOD/Lbioreactor*d and T = 2 days. Similar efficiency (333 LCH4/kg­FORBI) was achieved at higher OLR (4.53 gCOD/Lbioreactor*d). Highlights The feedstock used was a biomass product food residue biomass (FORBI), which is dried and shredded food waste.; Periodic anaerobic baffled reactor (PABR), a high-rate bioreactor.; The switching period (T) of the feeding compartment gives the bioreactor the element of operational flexibility.; The PABR can efficiently operate at HRTs as low as 2.5 days, however, the highest biomethane yield was achieved under HRT of 5 d.

This study measured the effect of low activated sludge dissolved oxygen (DO) concentration on a membrane bioreactor (MBR) treating real urban wastewater with respect to organic matter and nitrogen removal efficiency and transmembrane pressure evolution. For this purpose, a full-scale experimental pre-denitrification MBR system was operated at a constant permeate flow rate of Q = 0.45 m3h-1 with intermittent aeration. The experimental installation worked at high hydraulic retention time, variable sludge retention time and with activated sludge temperatures of between 22.0 to 31.3 °C. Mean DO concentrations in the activated sludge were gradually decreased from 1.25 mgO2L-1 to less than 0.20 mgO2L-1. Variations in DO set points did not affect the main operational parameters of the MBR system and no clear relation was shown between DO concentration decrease and membrane fouling. At DO concentrations lower than 0.2 mgO2L-1, a deterioration in MBR effluent quality was observed, mainly with respect to chemical oxygen demand, biochemical oxygen demand at five days and NH4+, however, the opposite effect was observed for NO3-. These results indicate that employing low DO set points is a promising strategy for application in MBR systems.

Constructed wetland is an alternative sewage treatment based on natural solutions, which can be applied as posttreatment of wastewater from conventional processes producing an effluent with excellent properties. In this study, over a period of 300 days, the removal of organic matter and nutrients (Nitrogen and Phosphorus) at different hydraulic retention times (2, 4 and 6 days) was evaluated. Three constructed wetlands with horizontal subsurface flow planted with Eleocharis sp. were operated as after-treatment of an aeration pond, which received municipal wastewater. Constructed wetland with the highest hydraulic retention time (6 days) was the one that obtained the best results in terms of organic matter (above 60%) and nutrients removal, reaching 74% of total phosphorus removal and 73% of total nitrogen removal. It was concluded that using constructed wetlands as posttreatment of aerated pond effluents proved to be promising as it enabled the maximization of nitrification due to the high presence of dissolved oxygen available in the bed, in addition to allowing the removal of organic matter and reaching high levels in removing nutrients.

Ceramic separators have recently been investigated as low-cost, robust, and sustainable separators for application in microbial fuel cells (MFC). In the present study, an attempt was made to develop a low-cost MFC employing a clayware ceramic separator modified with silica. The properties of separators with varying silica content (10%–40% w/w) were evaluated in terms of oxygen and proton diffusion. The membrane containing 30% silica exhibited improved performance compared to the unmodified membrane. Two identical MFCs, fabricated using ceramic separators with 30% silica content (MFCS-30) and without silica (MFCC), were operated at hydraulic retention time of 12 h with real rice mill wastewater with a chemical oxygen demand (COD) of 3,200 ± 50 mg/L. The maximum volumetric power density of 791.72 mW/m3 and coulombic efficiency of 35.77% was obtained in MFCS-30, which was 60.4% and 48.5%, respectively, higher than that of MFCC. The maximum COD and phenol removal efficiency of 76.2% and 58.2%, respectively, were obtained in MFCS-30. MFC fabricated with modified ceramic separator demonstrated higher power generation and pollutant removal. The presence of hygroscopic silica in the ceramic separator improved its performance in terms of hydration properties and proton transport. Highlights Ceramic separator modified with silica (30% w/w) outperformed unmodified separator.; 1.5 times more proton mass transfer was observed in ceramic separator with 30% silica.; Internal resistance of the MFC decreased 1.6 times due to better proton mobility.; Volumetric power density of 0.8 W/m3 and COD removal of 76.24% was achieved.; 1.5 times higher coulombic efficiency was obtained in the MFC operated with modified separator.

This study investigates the performance and hidden hydrogen consuming metabolic pathways of a fermentative side stream dynamic membrane (DM) bioreactor using flux balance analysis (FBA). The bioreactor was inoculated with untreated methanogenic seed sludge. It was found that fouling rate aggravated with increasing COD concentration (10–30 g/L) and was positively correlated to it rather than to the applied solid flux on the DM module. Due to increased fouling rate the hydraulic retention time (HRT) could not be reduced less than 0.82 ± 0.02 d. An increase in the organic loading rate (OLR) led to an increase in H2 yield from 0.01 to 0.76 mol H2/mol of sucrose. FBA revealed that homoacetogenesis was the main H2-consuming pathway at lower OLRs (corresponding to 10 and 15 g COD/L), while for the OLR corresponding to 30 g COD/L, homoacetogens were suppressed. More importantly, caproic acid production pathway was identified for the first time as another H2-consuming pathway at high OLR which was not significant at lower OLRs during fermentative dynamic membrane bioreactor operations.

The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor (MBR) treating synthetic hospital wastewater. The removal of four pharmaceuticals, namely carbamazepine, estradiol, venlafaxine, and ibuprofen in MBR, was studied at varying sludge retention time (SRT) duration of 100, 45, and 15 days and hydraulic retention time (HRT) of 18 h. The removal of ibuprofen and estradiol was constant at varying SRT; however, a negligible removal of carbamazepine and low removal of venlafaxine was observed (

Currently, effective methods to eliminate nitrate in wastewater with a low C/N ratio are urgently needed. Considering that sediment is the main nitrogen removal carrier in lakes and that woodchip is an excellent carbon source, this study was undertaken under an integrated system of these two substances to explore the process and efficiency of the denitrification involved. Using methods of kinetics and molecular biology, denitrification processes involving a woodchip-sediment system were investigated in an up-flow bioreactor (UFBR). Performance indices, functional genes, and microbial community changes in this integrated system were explored through water quality monitoring, quantitative PCR, and high-throughput sequencing. When the hydraulic residence time reached above 3.82 days, the nitrate elimination efficiency could achieve an effective level of higher than 93.3% even under the different flow rates. It was also noted that the nitrate elimination rate in this integrated system fitted the Michaelis–Menten kinetics, a combination of zero-order equation (R2 > 0.98) and first-order equation (R2 > 0.95). A combination of zero-order kinetic equations of nitrate elimination and total organic carbon (TOC) release exhibited nitrate elimination efficiency under direct influence of TOC release rate on the C/N ratio. Microbiological analysis indicated co-existence of composting bacteria and denitrifiers as well as aerobic degradation and heterotrophic denitrification, with the former process providing effective carbon sources for the latter process. This study provided a deep insight into the denitrification process of a woodchip-sediment integrated system, which might inspire a potential wastewater treatment method for reduced eutrophication in the aquatic environment.

The potential for obtaining renewable energy from organic substrates such as food waste (FW) and biowaste has generated increasing interest in the anaerobic digestion process. Kinetic models are used to analyse the impact of different parameters on biological processes and thus, to optimize them to achieve and to increase the quality and quantity of biogas. This study presents an approximation of the pre-dimensioning of semi-continuous anaerobic reactors treating FW, based on: (i) biochemical methane potential (BMP) assays, in different conditions of substrate-inoculum ratio (S/I: 0.5 and 4.0 g volatile solid-VSsubstrate·g VSinoculum−1) and nutrients (with macro-nutrients (N and P) and micronutrients, only micronutrients (Ni, Co, Mo and Fe) and without nutrients), and (ii) the kinetic performance through three kinetic models (transfer function-TF, logistic function-LF and modified Gompertz-MG), using Pmax (maximum methane production) and Rmax (maximum rate of methane production) as kinetic parameters related to the hydraulic retention time. The best S/I ratios were below 1.0 gVSsubstrate·gVSinoculum−1 with nutrients. Although the three kinetic models obtained a good fit (R2 > 0.9 and RMSE

This study investigated the effects of substrate concentration, HRT (hydraulic retention time), and pre-treatment of the substrate molasses on biohydrogen production from waste molasses (condensed molasses fermentation solubles, CMS) with a CSTR (continuously-stirred tank reactor). First, the hydrogen production was performed with various CMS concentrations (40–90 g COD/L, total sugar 8.7–22.6 g/L) with 6 h HRT. The results show that the maximal hydrogen production rate (HPR) occurred at 80 g COD/L substrate (19.8 g ToSu/L, ToSu: Total Sugar), obtaining an HPR of 0.417 mol/L/d. However, maximum hydrogen yield (HY) of 1.44 mol H2/mol hexose and overall hydrogen production efficiency (HPE) of 25.6% were achieved with a CMS concentration of 70 g COD/L (17.3 g ToSu/L). The substrate inhibition occurred when CMS concentration was increased to 90 g COD/L (22.6 g ToSu/L). Furthermore, it was observed that the optimal HPR, HY, and HPE all occurred at HRT 6 h. Operating at a lower HRT of 4 h decreased the hydrogen production performance because of lower substrate utilization efficiency. The employment of pre-heating treatment (60 °C for 1 h) of the substrate could markedly enhance the fermentation performance. With 6 h HRT and substrate pre-heating treatment, the HPE raised to 29.9%, which is 18% higher than that obtained without thermal pretreatment.

This study aims at improving the existing algal-based wastewater treatment technologies by overcoming some of the major drawbacks of these systems such as large required land area, culture contamination, and energy-intensive algal harvesting. The experiments were carried out in an open photo-sequencing batch reactor at a laboratory-scale for nearly 2 months. A specific strain ACUS00207 of the aeroterrestrial green microalga Klebsormidium nitens (Kützing) Lokhorst was used. The strain is native to Bulgaria and belongs to a species that has never been used before in suspended growth systems for wastewater treatment for phosphorus removal. The culture of K. nitens showed promising results: phosphorus removal rates ranging from 0.4 to 1 mg total phosphorus L−1 d−1, efficient settling properties, and resistance to culture contamination with native microalgae. On the basis of the observed phosphorus removal mechanism of biologically mediated chemical precipitation/phosphorus precipitation, an innovative working mode of the sequencing batch reactor is suggested for reducing the hydraulic retention time and the required land area. HIGHLIGHTS Klebsormidium nitens used for the first time in suspended growth wastewater treatment.; Phosphorus removal rates ranging from 0.4 to 1 mg total phosphorus L−1 d−1.; Efficient settling properties and resistance to culture contamination.; Potential for reduction of the hydraulic retention time and the required land area.

Naphthalene (NAPH) and phenanthrene (PHEN) are two of the most abundant polycyclic aromatic hydrocarbons (PAHs) found in nature, and they are considered in the list of US EPA priority pollutants. The contribution of this research lies in the comprehensive analysis of a strategy for the coupling of electro-oxidation (EO) and biodegradation in a submerged membrane bioreactor (SMBR) with the objective to remove PAHs, using NAPH and PHEN as model compounds. The electrochemical degradation of NAPH and PHEN in aqueous synthetic solution has been carried out using two different anodes: Ti/IrO2 and Ti/SnO2. The effects of EO operating parameters (current density, reaction time, and pH) on the NAPH and PHEN removals were investigated applying 23 factorial design with both electrodes. Additionally, the EO effluents were analyzed for COD, NH4-N, and biodegradability (respirometry tests). The highest removals of both compounds were reached with Ti/IrO2 anode, at acidic conditions (pH of 2), current density of 50 mA cm-2, and electrolysis time of 60 min. However, the Ti/SnO2 anode allowed greater reduction of the biomass inhibition, which means that the enhancement of the EO effluent biodegradability was reached; therefore, this electrode was selected for the coupled EO-SMBR system, applying the operating conditions that improved the biodegradability of the effluent. The EO process allowed NAPH and PHEN removal efficiencies of 96 ± 5% and 94 ± 3%, respectively. The membrane bioreactor was operated with organic load of 0.6 ± 0.1 gCOD gVSS-1 d-1, hydraulic retention time of 6 h, and solid retention time of 30 d, obtaining average COD, NH4-N, NAPH, and PHEN removals of 98±0.5%, 91±6.4%, 99.1±0.96%, and 99.7±0.4% respectively. The sorption of phenanthrene onto the biomass had a low contribution, 0.9±0.2%, concluding that biodegradation was the main removal mechanism in the bioreactor. The coupled system EO-SMBR allowed high NAPH and PHEN removal efficiencies of 99.99±0.01 and 99.99±0.02%, respectively.

This work aimed to (i) investigate the effect of hydraulic retention time (HRT) on controlling the release of phosphorus from sediment and (ii) interpret the phosphorus migration and transformation mechanism in the Al-PHOSLOCK thin-layer capping system. A 35-day laboratory dynamic simulation experiment was conducted by applying the Al-PHOSLOCK thin-layer capping to evaluate the effect of HRT on interrupting the release of phosphorus from contaminated sediments. The total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), non-apatite inorganic phosphorus (NAIP), and apatite phosphorus (AP) were identified as different phosphorus species and analyzed during the experiment to further elucidate the migration and transformation of phosphorus. The release of phosphorus from contaminated sediment was successfully suppressed by the Al-PHOSLOCK capping layer with an efficiency of higher than 90%. The HRT exerted a dual role on phosphorus controlling: at low HRT, slight water flow facilitated phosphorus migrating out from sediment and diffusing to the overlying water; at high HRT, the migration of phosphorus from overlying water back to sediment was strengthened. It was demonstrated that the phosphorus release was effectively controlled by the Al-PHOSLOCK thin-layer capping under different HRT conditions (static, 0.5 d, 1.0 d, and 3.0 d). The mechanism of phosphorus migration and transformation in the Al-PHOSLOCK thin-layer capping system was elucidated, including three significant stages of physical interception, adsorption, and capture/hold/transform process. This study verified the good capacity of the Al-PHOSLOCK capping system for controlling the release of sediment phosphorus under different HRT. Therefore, it was expected to be a promising approach in the handling of water eutrophication.

The coffee pulp is the solid waste most generated during the coffee humid pulping. It contains an elevated concentration of organic matter and lignocellulosic materials. In addition, the low rate of biodegradability of the coffee pulp waste may cause severe environmental damage. Therefore, the aim of this study was to evaluate the effect of acid and thermal pre-treatments in the biodegradability rate, followed by an anaerobic digestion of the coffee pulp and collect biogas production. Thermal and acid pre-treatments (50, 70, and 90 °C, and concentration of 2.5, 5, and 10% V·V−1 of acetic acid, respectively) were applied, both during 1 h, evaluating the organic matter solubilization. Posteriorly, the biodegradability and biogas production using anaerobic digestion for 35 days were evaluated. Finally, during 90 days in semicontinuous, the increase of applied organic load of 1 kg VS m−3 day−1 with Δ 1 kg VS m−3 day−1 every 30 days until reaching 3 kg m−3 day−1 was evaluated. The thermal pretreatment to 90 °C and 1 h improved the solubility and hydrolysis considered limiting of the anaerobic process, reducing the hydraulic retention time from 21 to 15 days, and increasing the biogas yields (0.92 L g VSrem−1 year 79.8% CH4).

This study aims to investigate the effect of substrate concentration and hydraulic retention time (HRT) on hydrogen production in a continuous anaerobic bioreactor from unhydrolyzed common reed (Phragmites australis) an invasive wetland and perennial grass. The bioreactor has capacity of 1 L and working volume of 600 mL. It was operated at pH 5.5, temperature at 37 °C, hydraulic retention time (HRT) 12 h, and variation of substrate concentration from 40, 50, and 60 g COD/L, respectively. Afterward, the HRT was then varied from 12, 8, to 4 h for checking the optimal biohydrogen production. Each condition was run until reach steady state on hydrogen production rate (HPR) which based on hydrogen percentage and daily volume. The results were obtained the peak of substrate concentration was at the 50 g COD/L with HRT 12 h, average HPR and H2 concentration were 28.71 mL/L/h and 36.29%, respectively. The hydrogen yield was achieved at 106.23 mL H2/g CODre. The substrate concentration was controlled at 50 g COD/L for the optimal HRT experiments. It was found that the maximum of average HPR and H2 concentration were 43.28 mL/L/h and 36.96%, respectively peak at HRT 8 h with the corresponding hydrogen yield of 144.35 mL H2/g CODre. Finally, this study successful produce hydrogen from unhydrolyzed common reed by enriched mixed culture in continuous anaerobic bioreactor.

In recent years, a lot of scientific effort has been put into reusing the energy potential of sugarcane vinasse by dark fermentation. However, the findings so far indicate that new pathways need to be followed. In this context, this study assessed the effect of hydraulic retention time (HRT, from 24 to 1 h) on vinasse fermentation (10, 20, and 30 g COD L−1) in three mesophilic expanded granular sludge bed reactors (EGSB). The carbohydrate conversion remained above 60% at all organic loading rates applied. The maximum hydrogen production rate (8.77 L day−1 L−1) was obtained for 720 kg COD m−3 day−1 and associated to the lactate-acetate pathway. The highest productivities of propionic, acetic, and butyric acids were 3.11, 1.68, and 2.45 g L−1 h−1, respectively, at a HRT of 1 h. At this HRT, the degrees of acidification remained between 54% and 76% in all EGSB reactors. This research provides insights for carboxylate production from sugarcane vinasse and suggests applying the EGSB setup in the acidogenic stage of two-stage processes.

This study explores an improved alternative on-site treatment for unsewered urban Bhutan. The system combines up-flow anaerobic sludge blanket for blackwater treatment and anaerobic biofilter for a mixture of up-flow anaerobic sludge blanket effluent and greywater. Shredded waste plastic bottles are used as novel biofilter media that provides a large surface area for attached growth while addressing waste plastic problems. A bench-scale up-flow anaerobic sludge blanket (operated at hydraulic retention time or HRT of 1–10 days) and anaerobic biofilter (HRT of 0.25–3 days) study were conducted for 188 days. At 2-d HRT, up-flow anaerobic sludge blanket removed 70–80 % of chemical oxygen demand (COD) while anaerobic biofilter achieved 90–98 % COD removal at eight-hour HRT. Combined up-flow anaerobic sludge blanket and anaerobic biofilter achieved final effluent with COD less than 50 mg/L and turbidity of less than 3 NTU that meets the discharge standard of Bhutan. The study shows that shredded waste plastic bottles can be an effective biofilter support medium for low-cost on-site treatment while helping address waste plastic problems.

A start-up study of lab-scale up-flow anaerobic sludge blanket fixed-film reactor (UASFF) was conducted to produce biohydrogen from palm oil mill effluent (POME). The reactor was fed with POME at different hydraulic retention time (HRT) and organic loading rate (OLR) to obtain the optimum fermentation time for maximum hydrogen yield (HY). The results showed the HY, volumetric hydrogen production rate (VHPR), and COD removal of 0.5–1.1 L H2/g CODconsumed, 1.98–4.1 L H2 L−1 day−1, and 33.4–38.5%, respectively. The characteristic study on POME particles was analyzed by particle size distribution (PSD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). The microbial Shannon and Simpson diversity indices and Principal Component Analysis assessed the alpha and beta diversity, respectively. The results indicated the change of bacterial community diversity over the operation, in which Clostridium sensu stricto 1 and Lactobacillus species were contributed to hydrogen fermentation.

This study reports on a new integrated valorization alternative for extracted olive pomace (EOP) by recovering polyphenols as high-value compounds and the subsequent anaerobic digestion of the remaining dephenolized fraction for energy production. The average polyphenol extraction rate was 22.10 kg GAE t−1 EOP and the subsequent optimum methane production from the remaining dephenolized fraction (278 L CH4 kg VS−1 d−1) occurred at organic loading rate (OLR) 2.48 g VS L−1 d−1 and 24 d hydraulic retention time (HRT). The study also reports on the preliminary economic feasibility study and the sensitivity analysis to valorize 1,500 t EOP y−1 under biorefinery concept. The calculated net present value (NPV) and internal return rate (IRR) were €1,996,856 and 58 %, respectively. The sensitivity analysis concluded that the minimum sales volume of hydroxytyrosol (HT) extract and the sale price per mass are by far the most significant factors that might influence the overall economic feasibility of the proposed EOP valorization plant.

The drinking water treatment plants (DWTPs) in the developing countries urgently need an efficient pre-treatment for nitrate (NO3−) removal to cope with the increasing NO3−pollution in raw water. An upflow sludge blanket (USB) reactor applied for NO3−removal from domestic wastewater may be adopted by the DWTPs. However, studies on the optimal carbon-to-nitrogen ratio (C/N) and operation of USB reactor at short hydraulic retention times (HRT) for high-rate polluted raw water pre-treatment are lacking. In this study, we first investigated the optimal C/N for biological NO3−removal in a sequencing batch reactor (SBR). An USB reactor was then operated with the optimal C/N for pre-treating synthetic raw water contaminated with NO3−(40 mg N L− 1) to monitor the NO3−removal performance and to examine opportunities for reducing the HRT. After operating the SBR with designed C/N of 4, 3 and 2 g C g− 1N, we selected C/N of 3 g C g− 1N as the optimal ratio due to the lower carbon breakthrough and nitrite (NO2−) accumulation in the SBR. The USB reactor achieved complete NO3−and NO2−removal with a lower designed C/N of 2 g C g− 1N due to the longer sludge retention time when compared with that of SBR (10 d). The high specific denitrification rate (18.7 ± 3.6 mg N g− 1mixed liquor volatile suspended solids h− 1) suggested a possible HRT reduction to 36 min. We successfully demonstrated an USB reactor for high-rate NO3−removal, which could be a promising technology for DWTPs to pre-treat raw water sources polluted with NO3−.

Due to water scarcity, storage and reuse of water has become a great challenge all over the world. The conventional methods for the wastewater treatment require large capital investment, operating cost, and need trained personal for supervision and maintenance. Therefore non conventional wastewater treatment methods have gained the popularity worldwide. Use of constructed wetland (CW) technology for wastewater treatment is highly efficient since CW are easy to construct, cost effective and increase the aesthetic value. Wetlands behavior and efficiency concerning wastewater treatment mainly depends upon macrophytes, substrate, hydrology, temperature and hydraulic retention time in the system. Present study deals with the removal of pollutants in two stage hybrid subsurface flow CW at different hydraulic retention times (HRT). The domestic wastewater was supplied to CW and treated using the available perennial macrophyte, Arundo donax. The system was run in replicate along with one control. To assess the removal efficiency of the pollutants, parameters like pH, temperature, dissolved oxygen (DO), total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) were analyzed at different HRT i.e., 36, 30 and 24 h. The result of the study observed maximum percentage removal of TSS, BOD, COD, and TKN was up to 84.61, 98.37, 61.39 and 91.87% respectively at 30 h of retention time.

This study involves continuous co-digestion of swine manure and pineapple waste mixture using two-stage anaerobic reactors and examines hydraulic retention time (HRT) and substrate heat pre-treatment. The maximum hydrogen and methane production rates of 1488.62 and 991.57 mL/L/d, respectively, reached optimal HRTs of 4.5 h in the hydrogen production fermenter (HPF) and 9 d in the methane production fermenter (MPF) using heat pre-treatment. Acetic acid is a dominant volatile fatty acid of the soluble metabolites with values 70%–73% under all the tested conditions and increased values under heat pre-treatment and high HRT. Firmicutes and Euryarchaeota are the main bacteria species detected in HPF and MPF, respectively. The optimal total energy of 196.47 kJ/L/d and chemical oxygen demand (COD) removal efficiency of 90% were obtained by a complete anaerobic co-digestion process at a high substrate concentration of 105 g COD/L and low HRT of 4.5 h. This shows that the two-stage co-digestion process could increase the COD removal efficiency, hydrogen production rate, and net energy gains and produce high quality biogas and significantly reduce fermentation time.

Despite the high prevalence of lactic acid bacteria in dark fermentation (DF) processes, their ecological role is not yet completely elucidated, preventing their systematic use as “helpers” for hydrogen production. The aim of this study was to investigate the microbial community structure of a lactate-driven DF process that successfully produced hydrogen under carbohydrate-limiting conditions using tequila vinasse as a substrate. Microbial responses to stepwise decreases in hydraulic retention time (HRT) from 24 to 4 h were assessed by using Illumina MiSeq sequencing. HRTs above 12 h and below 6 h led to a lower hydrogen production rate (HPR; 0.2–3.3 L/L-d) and process stability (HPR variations within 25–65%), which were associated with the presence of Acetobacter lovaniensis, Clostridium luticellari, Blautia coccoides, and the high abundance of propionate and lactate. Interestingly, transient conditions from unsteady-to-steady state occurred at an HRT of 12 h, where species richness and evenness decreased remarkably. Accordingly, HRTs between 12 and 6 h resulted in higher HPRs of up to 11.7 ± 0.7 L/L-d with HPR variations of less than 10%, which closely matched with the dominance of Clostridium sp., and butyrate and acetate as the main aqueous products. Overall, the results indicate that the successfulness of exploiting the ‘unwanted’ LAB proliferation through lactate-driven DF processes requires the enrichment of lactate-consuming and hydrogen-producing bacteria, which entails the selection of proper biocatalysts and operating conditions/strategies such as the operation of DF reactors under carbohydrate-limiting conditions and low HRTs.

This paper illustrates the method to predict the production of biohydrogen and biogas from the horizontal and vertical continuous mixed tank reactor using a numerical approach. Utilization of computational fluid dynamics on the estimation of bioreactor performance is very crucial owing to the uncertainty in the numerical results. Since there has been little work on CFD to determine the influence of hydraulic retention time, impeller speeds, vortex growth, and pH on biohydrogen yield rate the effort had been made. A series of simulations are done with optimal boundary conditions to ensure maximum hydrogen and biogas production rate. Two types of reactors HCSTR and VCSTR are operated at different impeller speed from 40 rpm to 120 rpm. Further, the rate of HRT and organic loading are varied. As the rpm of the impeller increase the rate of hydrogen and biomass production increases not later than 80 rpm. Meanwhile, the optimal range of HRT and pH are 4–8 h and 6.0–8.0. Running the impeller at optimized rate with derived conditions leads to high hydrogen and biogas production of 6 LH2/Ld and 30 L/d. The obtained results are validated with the experimental findings to compare the uncertainty formed due to the numerical simulations. The optimum boundary condition obtained from the study is expected to provide the essential knowledge in establishing the full-scaled reactors.

Volatile fatty acids (VFAs) are key platform chemicals used in a multitude of industries including chemicals, pharmaceuticals, food and agriculture. The current route for VFA production is petrochemical based. VFAs can be biologically produced using organic wastes as substrate, therefore directly contributing to a sustainable economy. This process is commonly known as acidogenic fermentation (AF). This review explores the current research on the development of AF processes optimized for VFA production. Three process steps are considered: feedstock pretreatment, fermentation, and primary product recovery with a focus on in situ recovery. Pretreatment is required for recalcitrant feedstocks, especially lignocellulosic substrates. Different pretreatment techniques for AF application have not been studied in depth. The operational parameters of AF (temperature, pH, hydraulic retention time, substrate concentration, etc.) highly influence microbial activity, VFA yields and product distribution. Optimum conditions are ultimately dependent on substrate composition, however, there is indication that certain operational ranges are beneficial for most feedstocks. VFA recovery and purification are necessary for chemical applications. When recovery is performed in situ, it can help relieve product-induced inhibition and keep alkalinity levels stable enabling further waste degradation. Many techniques have been tested, but none are directly compatible with the fermentation conditions tested. Bio-VFAs have the potential to aid in developing a circular economy, but further development is required. Processes need to be developed with the product market in mind, considering both process integration and systematic process optimization.

Proportions of biogas effluent, sugarcane filter cake, and anaerobic sludge for methane production were optimized in batch fermentation using a mixture design with the D-optimal design method. The highest methane yield (MY) of 175.1 mL CH4/g volatile solid (VS) was achieved at a biogas effluent and filter cake of 30.00 and 30.00 g VS/L, respectively. Results suggested that the methane production could occur by normal floras in biogas effluent and filter cake without the addition of inoculum. The data from batch experiments were used to evaluate the hydraulic retention time (HRT) by the first-order kinetic model. The optimum proportions and predicted HRT of 30 days were further used to determine their efficacy in generating methane in the semi-continuous fermentation process using the continuous stirred tank reactor (CSTR). It was confirmed that the optimum proportions and HRT of 30 days gave a maximum MY of 92.8 mL CH4/g VS and methane production rate of 185.9 mL CH4/L day.

Excessive use of nitrate fertilizers in agriculture causes harm to humans and the environment. The most suitable nitrate removal process is heterotrophic biological denitrification. The purpose of the present study was to evaluate the performance of three shapes of denitrification bioreactors: triangular, rectangular and semicircular. The main element that was used to remove nitrate was beech woodchips. The concentration of inlet nitrate was 75 mg/l and the salinity of the solution was 1 ds/m and 5 ds/m, for a period of six months. The results showed that the efficiency of the triangular bioreactor with a salinity level of 1 ds/m was 90%, which is more efficient than the rectangular and semicircular bioreactors with performances of 55.8% and 53.8%, respectively. The results also indicated that at a salinity level of 5 ds/m, the semicircular bioreactor with a performance of 50.8% inlet nitrate removal was the best of the three shapes of bioreactors tested, the efficiencies of the triangular and rectangular bioreactors were 49.9% and 48.6% respectively. Also, it was observed that at the salinity level of 1 ds/m, a high hydraulic retention time had a high positive effect on denitrification, on the other hand at the salinity level of 5 ds/m, there was better performance of denitrification if the hydraulic retention time was lower.

Dewatering of sludge is a key problem that must be solved in the sewage sludge disposal industry. In this study, a series of process optimization tests were conducted to learn how to improve sludge treatment. The optimum process of sludge leaching treatment was studied in a specially designed 100-L reactor system. Four factors were investigated and nine batches of bioleaching tests were run at three levels of these factors. Orthogonal experiments showed that the effect of sludge return ratio and aeration rate on the sludge moisture content was significant and hydraulic retention time (HRT) had a clear effect, but nutrient types had a reduced effect on the moisture content of sludge. The primary and secondary order of each factor is reflux ratio > aeration rate > HRT > nutrient type. Under the optimal process, three batches of sludge were processed and the moisture content of the filter press cake was reduced to less than 60%, the organic matter content reduced to below 5%, and the concentration of heavy metals (Cu, Zn, Pb, and Cr) was much lower than the agricultural standard limit, which is suitable for landscaping, composting, and incineration power generation and other resource applications.

In municipal wastewater treatment, controlling the stability and efficiency of the anaerobic process is the premise and key to the high-standard discharge of organic matter and total nitrogen. In this study, two types of hydrolytic acidification, immobilized biological active fillers and traditional activated sludge, were used to treat municipal wastewater at different temperatures (13−24℃) and working conditions. The degradation of organic matter and the transformation of organic nitrogen in the anaerobic process were compared, and the internal flora of the immobilized fillers was systematically analyzed by high-throughput sequencing technology. The results show that the filler exhibited higher activity at low temperatures, and the residual organic nitrogen level in the effluent (0.3−0.5 mg L−1) was significantly lower than that in the sludge reactor (0.8–1.2 mg L−1). The performance of hydrolysis-acidification of skeleton-less fillers (EB3) was higher than that of skeletoned fillers (EB2) (the hydraulic retention time was 1 h and fill rate was 8%). The organic nitrogen of fillers was completely converted, while the volatile fatty acid of EB3 effluent increased by 2–2.5 mg L−1, greater than the increase in EB2 effluent (0.9–1.3 mg L−1). Based on the results of high-throughput sequencing, the fillers contained the same functional species, albeit at different abundances. The immobilized fillers could improve the performance of traditional activated sludge to maintain biomass through reflux and achieved the dual advantages of fixing biomass and maintaining good anaerobic characteristics.

Water hyacinth ( Eichhornia crassipes ) causes ecological and economic problems because it grows very fast and quickly consumes nutrients and oxygen in water bodies, affecting both the flora and fauna; besides, it can form blockages in the waterways, hindering fishing and boat use. However, this plant contains bioactive compounds that can be used to produce biofuels. This study investigated the effect of various substrates as feedstock for biogas production. A 125-l plug-flow anaerobic digester was utilized and the hydraulic retention time was 14 days; cow dung was inoculated into water hyacinth at a 2:1 mass ratio over 7 days. The maximum biogas yield, achieved using a mixture of natural water hyacinth and water (NWH-W), was 0.398 l/g volatile solids (VS). The cow dung/water (CD-W), hydrothermally pretreated water hyacinth/digestate, and hydrothermally pretreated water hyacinth/water (TWH-W) mixtures reached biogas yields of 0.239, 0.2198, and 0.115 l/g VS, respectively. The NWH-W composition was 70.57% CH 4 , 12.26% CO 2 , 1.32% H 2 S, and 0.65% NH 3 . The modified Gompertz kinetic model provided data satisfactorily compatible with the experimental one to determine the biogas production from various substrates. TWH-W and NWH-W achieved, respectively, the shortest and (6.561 days) and the longest (7.281 days) lag phase, the lowest (0.133 (l/g VS)/day) and the highest ( 0.446 (l/g VS)/day) biogas production rate, and the maximum and (15.719 l/g VS) and minimum (4.454 l/g VS) biogas yield potential.

This study investigated the external operational factors that would reduce the thermodynamic constrains preventing the simultaneous achievement of high hydrogen productivities (HPs) and hydrogen yields (HYs) in the bioreactor. At hydraulic retention time (HRT) of 1, the maximum HPs and HYs achieved was 35 L H2/h and 3.91 mol H2/mol glucose, respectively. At this stage, the bacterial granules occupied approximately 75% of the bioreactor and consisted of the settled biomass density of 40.6 g/L (settled granule bed height = 13.8 cm). The formation of bacterial granules improved the bioreactor performance and resulted in higher substrate conversion efficiency (95%), nutrient influent (7.5 L/h) and de-gassed effluent recycle rates (3.5 L/min). In conclusion, this study demonstrated that high nutrient influent and high de-gassed effluent recycle rates reduced the thermodynamic constrains preventing the achievement of higher H2 productivities in the bioreactor system.

Increasing demand for dairy products resulted in the development of a large number of dairy industries, generating wastewater of high pollution potential. Main wastes generated include whey residues, milk fat and proteins, dairy sludge, and liquid effluents produced through different lines (cleaning, processing, and sanitary). Anaerobic digestion technology has got wide acceptance in recent times for treating highly organic effluents like dairy wastes due to its added benefits like energy recovery and high waste stabilisation with less energy requirement. This review paper is aimed at studying the effects of different key parameters (pH, carbon-to-nitrogen ratio, temperature, organic loading rate, solid retention time, hydraulic retention time, alkalinity, and mixing) on the successful operation of an anaerobic digester and thereby enhancing biogas production efficiency. Different waste streams generated in the dairy industry are identified along with their important characteristics. The process chemistry of anaerobic degradation of various effluents generated from the dairy industry is discussed. The need for pre-treatment technologies and the scope of co-digestion of dairy wastewater with other organic wastes are also covered. This critical review is intended to summarise the present knowledge on the application of anaerobic methods for treating dairy wastes most efficiently with proper control over operational parameters while maximising the biogas yield.

The adaptability of a thermophilic anaerobic digester stabilized long-term with poultry litter as sole feedstock was measured with regard to co-digestion with dairy cattle manure. Both feedstocks have low C/N ratios but differ in carbohydrates, protein, and fiber content. The digester was a pilot-scale (40 m3) sCSTR (semi-continuously stirred tank reactor) with a 20-day hydraulic retention time (HRT). Dairy manure was added as three step-wise increases in concentration: 20, 40, and 80%. At 20% dairy manure, methane production was unchanged (17–19 m3 day−1). But as the fraction of dairy manure increased, methane, ammonia, sCOD, acetate, and propionate decreased. At 80% dairy manure, methane volume dropped by 60%. Acetate concentration decreased from an initial 878 ± 209 mg L−1 during poultry litter mono-digestion to 285 ± 169 mg L−1 with 80% dairy manure. Upon returning to mono-digestion, methane production was on a trajectory of recovery although acetate remained low. Bacterial community structure shifted during co-digestion, but community resilience was also underway following return to the original feedstock for one HRT. The dominant bacterial phylotypes belonged to the groups Thermotogales, Synergistales, Clostridiales, and Halanaerobiales, and three uncharacterized orders (MBA08, SHA-98, OPB54) in class Clostridia. Co-digestion led to a shift in dominance with reductions in Thermotogales and OPB54, and an increase in MBA08. This experiment provides guidance for digester operators who wish to mix livestock and poultry manures for thermophilic co-digestion.

As one of the low-impact development measures, bioretention plays an important role in reducing the runoff peak flow and minimizing runoff pollutants, such as heavy metals, suspended solids, and nutrients. However, the efficiency of nitrogen removal in the bioretention system is unstable, owing to the different chemical properties of various forms of nitrogen and the limitations of current bioretention system for nitrogen transformation. This review article summarizes the recent advances in bioretention system in treatment of urban stormwater and agricultural runoff for nitrogen removal. The microbial characteristics and main processes of nitrogen transformation in bioretention are reviewed. The operational conditions affecting nitrogen removal, including climatic conditions, pH, wet-dry alternation, influent loads and nitrogen concentration, and hydraulic residence time are discussed. Finally, measures or strategies for increasing nitrogen removal efficiency are proposed from the perspectives of structural improvement of the bioretention system, optimization of medium composition, and enhancement of the nitrogen removal reaction processes.

Four agricultural wastes, i.e., sugarcane bagasse, rice straw, cotton stalk, and corn stalk were experienced as low-cost lignocellulosic materials for their ability to adsorb reactive red dye from its contaminated solutions. Batch adsorption technology was carried out in order to analyze sorption behavior of dye-adsorbent systems at different wastes, initial dye concentration, and solution pH value. The acid pH treatment was detected to significantly enhance the adsorption efficiency of used lignocellulosic wastes to maximum removal efficiency (96%). Bioreactor technology was applied as up-scaling experiments using sugarcane bagasse (SCB) waste (the best adsorbent under batch experiments) with different adsorbent dosage and flow rates. The maximum removal efficiency (89.65%) was recorded by 448 g of SCB waste, hydraulic retention time of 24 h and 12.6 l/h flow rate. The SEM characterization illustrated accumulation of dye molecules onto lignocellulosic structure. Also, elemental analyses by EDAX instrument confirmed absorption technology. Thus, the sugarcane bagasse wastes can be applied as low-cost and environmental safe absorbent for RR dye removal from its contaminated wastewater and introducing non-traditional water resource.

This study aimed to evaluate the effect of organic loading rate (OLR) variation on the anaerobic treatment of food waste from a university restaurant in a demonstration-scale set-up. The system was submitted to the academic calendar and seasonal variation of temperature. During 330 days of semi-continuous operation in three different periods (i.e. school-period/fall, school-period/spring and vacation-period/summer), the reactor performance and stability process were analysed. The reactor temperature was not controlled and varied seasonally from 23 to 32 °C. Differently, the OLR and hydraulic retention time (HRT) were controlled by food waste available in the vacation period and by the reactor stability in the school periods, ranging from 0.15 to 0.51 kg VS m−3 day−1 for the OLR and from 121 to 230 days for the HRT. The highest average methane production rate and VS removal were 0.12 m3 CH4 m−3 day−1 and 81%, respectively. The results indicated that as the reactor had been operated using non-optimized mixing for six years before the experiment, probably the accumulation of inert materials inside affected its performance. In addition, despite the non-optimized mixing of the reactor, which represented up to 80% of the energy consumed, a net energy ratio of 1.98 was achieved. Throughout the experimental period a total of 15,970 kg of food waste was treated and 375 m3 of methane were produced. Despite the system limitations, the valorization of food waste through anaerobic digestion proved to be possible under simplified operating conditions, i.e. even without pH and temperature control, besides the organic loading rate reduction caused by the vacation period.

The simultaneous digestion of two or more organic substrate in anoxic conditions is a proven strategy for optimizing anaerobic digestion (AD) efficiency, likewise, the maintenance of process temperature within the biocatalytic range of AD processes is critical for process stabilization. However, challenges with yield and process stability yet presents major bottlenecks for bio-digester designs specifically for low-income households due to characteristic limitations in feed profile and constant exposure to natural elements and fluctuations in weather conditions. In this study, knowledge of common advantages of co-digestion of kitchen wastes and animal manure; nutrient balancing for improved microbial growth and activity, augmentation of substrate characteristics, was combined with household digester design modification (with low-density polyethylene (LDPE) cover) for an improved, yet techno-feasible process. Low-cost, durable LDPE commonly used for its greenhouse heating function was explored here for sustaining bio-methane production from organic feeds in and at household digester conditions. Food wastes (KW) was co-digested with cow manure (CW) in a modular anaerobic digester with and without LDPE cover. Findings showed the optimum feed blend: KW to CW, 3:1 produced the highest amount of biogas over a hydraulic retention time of 30 days and organic loading rate of 4.41 kgVS/L/day. The co-digestion runs suggested significant synergy across runs while mono-digestion of KW failed due to acidification. Fed-batch codigestion of the substrates in the LDPE modified digester resulted in a significant increase in methane content of produced biogas with proof of slurry temperature within the mesophilic range (29–44 °C) across the 3-month study time.

The main objective of the present study was to demonstrate microaeration as an effective strategy to boost the biotransformation of four parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in an upflow anaerobic sludge blanket reactor operated at a short hydraulic retention time (8 h). Moreover, the effect of different airflow rates (1−4 mL min−1) was also assessed from an engineering and microbiological perspective. Low mean removal efficiencies (REs) (14–20 %) were achieved under anaerobic conditions. However, the addition of only 1 mL air min−1 (0.027 L O2 L−1 feed) remarkably boosted the biotransformation of parabens, ensuring mean REs above 85 % for all compounds. In contrast, the increase in the airflow rate had a minor impact on the process, and an apparent saturation in the removal capacity was observed, noticeably from 2 to 4 mL air min−1. The reactor presented high stability throughout the experiment, and microaeration did not impair the organic matter removal and methanogenesis. However, high airflow rates can dilute biogas, compromising its use as a fuel in combined heat and power units. The microaerobic conditions increased both richness and diversity of the reactor’s microbiota, likely favoring the growth of oxygenase-producing microorganisms, which may have played a role in the biotransformation of parabens. Finally, the high REs of parabens reached in the microaerated reactor, a more cost-effective technology, are comparable to those found in high-cost wastewater treatment systems, such as activated sludge and its variants.

This study investigates enhancing the biogas production of sunnhemp by pretreatment, before the anaerobic digestion and co-digestion processes, to address the complex and recalcitrant structure of the plant. Fresh sunnhemp harvested at a cutting interval of 50 days is used in the study. Five systems (each with a 5 litre useable volume) are operated semi-continuously with five different ratios of the feedstock by feeding separate feedstocks every five days with a hydraulic retention time (HRT) of 40 days. The system operates at room temperature (30 °C). The study uses sunnhemp as 20% of the feedstock and also considers sunnhemp mixed with cow manure at different ratios, with the weighed sunnhemp being pretreated with dilute sodium hydroxide. Pretreatment of sunnhemp before digestion produces a methane (CH4) yield 89% greater than that of the untreated sunnhemp. It requires 3.597 kg of dry sunnhemp to produce 1 m3 of CH4 and the annual CH4 yield per hectare is 19,015 m3. In the pretreatment of sunnhemp before co-digestion, the increased CH4 yield depends on the amount of pretreated sunnhemp in the feedstocks. However, the %CH4, the CH4 production level and the system stability depend on the optimal ratio of the sunnhemp to cow manure. The initially prepared sunnhemp to cow manure ratio is recommended at 10 g:10 g in 80 mL of water. At this ratio, the %CH4 and the CH4 yield are 53.84% and 313 kg chemical oxygen demand (COD) removed, respectively, and the COD removal efficiency is 56.4%. Sunnhemp has high potential and it is worth pretreating before producing biogas. Using sunnhemp to produce biogas is recommended to decrease greenhouse gas emissions and mitigate global warming.

An up flow anaerobic sludge-fixed film (UASFF) reactor could be a granular sludge bioreactor that was used for the fast-biological conversion of organic concern biogas with the aids of aggregative microbic association. The major downside related to the traditional UASB reactor is that the long period for start- up amount, during this study, UASFF bioreactor with granular flow behaviour was developed to shorten the start-up amount at low Hydraulic Retention Time. The huge quantities of water and totally different chemicals area unit required throughout a dairy plant. The degree of water used in an exceedingly dairy trade varies with connection the provision of water, methodology and sort of flow. The wastewater once every step of method is discharged into either the natural water bodies or to the setting that alters the ecological balance. This analysis work on the laboratory scale model is utilized for the analysis and treatment of farm trade effluent. This study evaluates the influence of Organic Loading Rate in the biodegradation performance of a lab scale hybrid up flow anaerobic sludge fixed film (UASFF) reactor for treating synthetic dairy industry wastewater. The lab scale UASFF reactor was designed and fabricated for an effective volume of 13L with Fujino spiral as packing media at the top of reactor and operated in continuous mode. The reactor was operated for different Organic Loading Rate ranging from 0.28 kg COD/m3. d to 2.33 kg COD/m3. d by varying the influent COD concentrations of 8500 mg/L,10000 mg/L, 11500 mg/L, 13000 mg/L and 14500 mg/L under steady state condition.

Increasing population, urbanization and changing lifestyle has led to enormous generation of municipal solid waste which is ultimately disposed in sanitary landfills leading to the problem of leachate pollution. Leachate needs to be treated with an effective method before its disposal. Among various options available the treatment using anaerobic technology is preferred in this study. The performance of a modified anaerobic baffled reactor (MABR) treating landfill leachate containing heavy metals at different organic loading rates (OLRs) was investigated in this study. The MABR was seeded with granular sludge taken from an anaerobic digester and fed gradually with landfill leachate at OLRs of 1.4, 1.86, 2.8 and 5.6 kgCOD/m3/d at hydraulic retention time (HRT) of 4,3,2 and 1d, respectively. Experimental results revealed that 76% chemical oxygen demand (COD) removal was achieved at the OLR of 1.4 kgCOD/m3·d. However, when the OLR was increased to 5.6 kgCOD/m3/d, a minor decrease in the COD removal efficiency (70%) was observed. Heavy metals such as arsenic (As), Chromium (Cr), Iron (Fe) and color removal values decreased from 88%, 89%, 88%, and 78% to 8%, 59%,64%, and 37% respectively. Overall Biogas production showed the increasing trend from 0.1, 0.15, 0.32 and 0.4 L/d at OLRs of 1.4, 1.86 and 2.8 and 5.6 kg COD/m3/d, respectively. There was no significant difference in the pH profiles (8.0–8.6) and volatile acids (VA) during the variation of OLRs (1.4–5.6 kgCOD/m3/d). The VA concentration in the effluent (CH4) of the reactor was in the range of 37 to 57 mg/L HOAC, indicating the fatty acids were utilized by the microorganisms. Toxicity caused by heavy metals in the bioreactors is one of the problems of concern in the treatment of wastewaters. This study evaluated the performance of MABR in the treatment of landfill leachate containing arsenic (As), Chromium (Cr), Iron (Fe) and the production of biogas by varying the hydraulic retention time (HRT) and subsequently, organic loading rate (OLR). The study reveals that MABR system can be used efficiently in the treatment of landfill leachate.

4-chlorophenol (4-CP) is a hazardous contaminant that is hardly removed by some technologies. This study investigated the biodegradation, and physical 4-CP removal by a mixed microbial consortium in the Airlift packed bed bioreactor (ALPBB) and modeling by an artificial neural network (ANN) for first the time. The removal efficiency of ALPBB was investigated at 4-CP(1-1000 mg/L) and hydraulic retention time (HRT)(6-96 hr) by HPLC. The results showed that removal efficiency decreased from 85 at 1 to 0.03% at 1000 mg/L, with increasing 4-CP concentration and HRT decreasing. BOD5/COD increased with increasing exposure time and concentration decreasing, from 0.05 at 1000 to 0.96 at 1 mg/L. With time increasing, the correlation between COD and 4-CP removal increased (R2 = 0.5, HRT = 96 h). There was a positive correlation between the removal of 4-CP and SCOD by curve fitting was R2 = 0.93 and 0.96, respectively. Moreover, the kinetics of 4-CP removal follows the first-order and pseudo-first-order equation at 1 mg/L and other concentrations, respectively. 4-CP removal modeling has shown that the 2:3:1 and 2:4:1 were the best structures (MSE: physical = 0.126 and biological = 0.9)(R2allphysical = 0.999 and R2testphysical = 0.999) and (R2allbiological = 0.71, and R2testbiological = 0.997) for 4-CP removal. Also, the output obtained by the ANN prediction of 4-CP was correlated to the actual data (R2physical = 0.9997 and R2biological = 0.59). Based on the results, ALPBB with up-flow submerged aeration is a suitable option for the lower concentration of 4-CP, but it had less efficiency at high concentrations. So, physical removal of 4-CP was predominant in biological treatment. Therefore, the modification of this reactor for 4-CP removal is suggested at high concentrations.

Biological treatment of nitrate in reverse osmosis (RO) concentrate produced from municipal wastewater effluent is challenging, in part because of the low carbon-to-nitrogen ratio. Open-water unit process wetlands may provide a cost-effective means of removing nitrate because autotrophic production of labile organic carbon supports denitrification in the wetland biomat. To determine the potential for employing open-water unit process wetlands for removing dissolved nitrogen species from RO concentrate, a pilot-scale open-water wetland treatment system was established and studied over a two-year period at a water reuse facility in San Jose, California. The system was operated with a 3-day hydraulic residence time, resulting in removal of up to 30% of the nitrate present in the RO concentrate during the first summer of operation and removal of up to 47% of the nitrate during the second summer. The biomat comprised a diverse algal and heterotrophic bacterial assemblage containing several clades that are putatively capable of denitrification, as well as greater abundances of denitrifying functional genes (nirK, narG) in the second year, coincident with higher nitrate removal. In batch reactors, the addition of woodchips increased nitrate removal rates from RO concentrate by approximately a factor of five or more, with rates dependent on the dose of woodchips applied. These results indicate that woodchip amendments could reduce the land area needed for nitrate treatment. This study provides evidence that open-water wetlands can remove nitrate from RO concentrate at the pilot scale, and identifies opportunities to enhance treatment efficiency with low-cost carbon amendments.

The improvement on biogas production from anaerobic digestion system requires a meticulous analysis in troubleshooting especially in the case of meltdown or failure. The involvement of rapidly mutated bio-organism is a major setback to instantly trace and correct the faults in the system. Fractional factorial design was applied in this study to improve the process troubleshooting in STP. It was performed using five control parameters including pH (A), total solid (TS), feedstock recirculation (FR), inoculum percentage (IP) and hydraulic retention time (HRT) on the biogas production. The results demonstrate that pH (6.0), TS (4.0%), feedstock recirculation (4%), inoculum percentage (33%) and sludge retention time (14 days) produced the highest yield of biogas. Four significant effects for the process passed the Bonferroni limit, with two interaction effects between CD (FR and IP) and BE (TS and HRT) with 19.59% and 11.36% percentage contribution. A strict yet suitable amount of inoculum, time, and substrate was acquired in the high-efficiency process. The rest were the main factors of E: HRT with 15.27% and A: pH with 12.69% contribution demonstrates the importance of contact time between microbe and substrate, and the process environment. The outcome from the study proves that, the improvement of process troubleshooting using factorial analysis is highly beneficial and useful to sustain an efficient digestion system.

Cell immobilization can be characterized as any strategy that restrains the free development of cell. The Sequencing Batch Reactor is utilized for the expulsion of alkali utilizing Nitrifying Bacteria by immobilized in sodium alginate beads. The ammoniacal nitrogen removal efficiency was evaluated at different pH from 7 to 9 and different nitrogen loading rates from 150 to 350 mg/L and hydraulic retention times (HRT) of 24, 48 and 72 h. The optimization of operating parameters such as pH, nitrogen loading rate and HRT was studied. The influent and effluent was analyzed for ammoniacal nitrogen, nitrite nitrogen and nitrate nitrogen. The highest removal of ammoniacal nitrogen was accomplished (89%) at pH 8 and the nitrogen loading rate of 350 mg/L with 72 h hydraulic retention time. The result indicates that the removal efficiency of ammoniacal nitrogen increase with increase in HRT and Nitrogen loading rate. Smelling salts oxidizing microorganisms were immobilized by polyvinyl liquor (PVA) and sodium alginate. The immobilization conditions and smelling salts oxidation capacity of the immobilized microscopic organisms were explored. The accompanying immobilization conditions were seen to be ideal: PVA-12%; sodium alginate-1.1%; calcium chloride-1.0%; inoculum focus-1.3 immobilized balls/mL of immobilized medium; pH-10; and temperature-30 °C. The immobilized smelling salts oxidizing microscopic organisms displayed solid alkali oxidation capacity significantly subsequent to being reused multiple times. The smelling salts nitrogen expulsion pace of the immobilized alkali oxidizing microscopic organisms arrived at 90.30% under the ideal immobilization conditions. When contrasted and smelling salts oxidizing microorganisms immobilized by sodium alginate alone, the microscopic organisms immobilized by PVA and sodium alginate were better with deference than pH opposition, the quantity of reuses, material cost, heat obstruction, and alkali oxidation capacity.

The objective of the present study was to evaluate the influence of the carbon/phosphorus (C/P) ratio (300–1100) on hydrogen production and the control of homoacetogenesis in four anaerobic fluidized bed reactors with fixed carbon/nitrogen ratios of 100, 150, 200, and 250. The reactors were fed glucose (5000 mg L−1) at the hydraulic retention time (HRT) of 8 h. Low production of acetic acid attributed to homoacetogenesis was observed in all reactors (

In this study, we investigated the feasibility of anaerobic sewage treatment at extremely low temperatures (4 °C) using two reactor setups: upflow anaerobic sludge blanket reactors (UASB) without and with (AnMBRUASB(UF)) a membrane. Both reactors were inoculated with seeds derived from sediments that were putatively acclimatized to low temperatures. A preliminary batch trial showed that treatment is feasible with the removal of carbon coupled to methane and sulphide production. The reactors operated for 180 days at a hydraulic retention time of 3 days. After 40 days acclimation, both systems met the EU chemical oxygen demand (COD) effluent standard (

Encapsulation technology has been extensively investigated for various microbiological applications for decades. Combined with biological processes, encapsulated bacteria have great potential to efficiently and cost-effectively recover resources (e.g., hydrogen, methane, metals) from various waste streams, such as wastewater, metal wastes, and sludge. This review focuses on recent advances in four areas: encapsulation of specific bacteria or biocatalysts, effectiveness in separating the solids retention time from the hydraulic retention time, control of the encapsulant internal environment, and improved reusability and storability of encapsulated bacteria. In most cases, encapsulation technology enhanced biological resource recovery by facilitating stable high-rate operation; nevertheless, challenges remain that limit application. Consequently, this review points to three major research opportunities that, if addressed, could enable broader application of encapsulated bacteria for resource recovery: (1) encapsulant impacts on bacterial growth, leakage, and community changes with time, (2) use of encapsulant chemistry to control the encapsulant internal environment, and (3) modifications of the encapsulant matrix to improve the reusability and storage of bacteria. With the better control and predictability that should result, the use of encapsulation technology in biological processes could be further advanced as a reliable and efficient option for resource recovery.