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Bioponics integrates the biological treatment of nutrient-rich waste streams with hydroponics. However, there are several challenges of bioponics, especially nutrient availability and qualities, which affect plant yield. In this study, chicken manure based-nutrient film technique bioponics was examined at manure loadings of 200, 300, and 400 g dry wt. per bioponic system (total of 18 plants). Bioponics effectively released nitrogen and phosphorus (total ammonia nitrogen of 5.8–8.0 mgN/L, nitrate of 7.0–11.2 mgN/L, and phosphate of 48.7–74.2 mgP/L) for efficient growth of lettuce (Lactuca sativa; total yield of 1208–2030 g wet wt. per 18 plants). Nitrogen and phosphorus use efficiencies were 35.1–41.8% and 6.8–8.0%, respectively, and were comparable to aquaponics. Next-generation sequencing was used to examine the microbial communities in digested chicken manure and plant roots in bioponics. Results showed that several microbial genera were associated with organic degradation (e.g., Nocardiopsis spp., Cellvibrio spp.), nitrification (Nitrospira spp.), phosphorus solubilization, and plant growth promotion (e.g., WD2101_soil_group, and Bacillus spp.). Nocardiopsis spp., Romboutsia spp. and Saccharomonospora spp. were found at high abundances and a high degree of co-occurrences among the microbiota, suggesting that the microbial organic decomposition to nitrogen and phosphorus release could be the key factors to achieve better nutrient recovery in bioponics.

This document it is established that 2 types of biogas anaerobic digester that usually found in developing country. First type is fixed dome type of anaerobic digester and secondly is floating drum biogas anaerobic digester. Both of this type have draw back that the anaerobic process is not completed with agitation process that yield low rate of biogas production. Other serious problem is the release of slurry cannot optimal. Some of the slurry will still remain stay in the anaerobic digester especially scum. To drain and cleaning the fixed dome or floating drum biogas anaerobic digester is mandatory to be done regularly that consume time and cost. The fixed dome types as well as floating drum type are usually not portable which cause no possibility to relocate in the new site. It is the purpose of this work to introduce portable biogas anaerobic digester that suitable for developing country with volume of digester around 500 liter of slurry. The requirement of agitator is facilitated, and the anaerobic digester is possible to be operated in batch system or continuous system. The material that is used for anaerobic digester is stainless steel 304 with tungsten inert gas welding technology that is used for the manufacturing. With this design the anaerobic digester are easy to be maintenance. The batch system can keep producing biogas until 52 day with total production of biogas around 3320 liters. The continuous system was conducted by releasing for about 5 liters slurry from the outlet and after that filled with new slurry with stirring with agitator was conducted for about 10 minutes for 3 times in a day (morning, noon, and evening). The result for continuous system is a linear biogas production with rate biogas production is around 51.7 liter/day (1550 liter/30days).

While rumen microorganisms are known to facilitate the hydrolysis of lignocellulosic substrates in anaerobic digestion (AD), it is unclear how rumen content can be used to maintain rumen microorgan...

Environmental contamination of heavy metals is now becoming increasingly a concern and a significant problem due to its harmful effects worldwide. The plant-meditated approach is encouraging to eliminate toxins avoiding side effects from polluted wastewater. For the development of appropriate plant species for the mechanisms of heavy metal absorption, transport, detoxification, identification, and signaling pathways would be important facts. Transporter genes like ATP-phosphoribosyl transferase (ATP-PRT), Yellow Stripe-like (YSL), NAS (nicotinamide synthase), SAMS (S-adenosyl-methionine synthetase), FER (ferritin Fe (III) binding), HMA (heavy metal ATPase), IREG (iron-regulated transporter), and proteins like cation diffusion facilitators (CDF), ZRT, IRT-like protein (ZIP), and natural resistance-associated macrophage protein (NRAMP) are active in heavy metal accumulation, translocalisation, sequestration, and resistance. Besides, chelating agents and metabolites can be used either to increase heavy metal bioavailability, which facilitates heavy metal accumulation in plants and further promote plant growth and fitness. This review paper addresses key roles and potential transporter genes and proteins for the remediation of heavy metals from hyperaccumulator plants. This review specifically focuses on the efficacy of transporter genes and proteins in hyperaccumulator plants in metal restoration, discussing the use of these plants for wastewater treatment processes.

In this study, we examined eight typical and widely detected pharmaceuticals (PhAs) removal in an anaerobic sulfate-reducing bacteria (SRB) sludge system (five antibiotics: sulfadiazine (SD), sulfamethoxazole (SMX), trimethoprim (TMP), ciprofloxacin (CIP) and enoxacin (ENO), and three nonsteroidal anti-inflammatory drugs (NSAIDs): ibuprofen (IBU), ketoprofen (KET) and diclofenac (DIC)). The results showed that the SRB sludge had the higher removal efficacy (20 to 90%) for antibiotics (SD, SMX, TMP, CIP and ENO) than NSAIDs (

Anaerobic digestion (AD) of lignocellulosic biomass has received significant attention for bioenergy production in recent years. However, hydrolysis is a rate-limiting in AD of such feedstock. In this study, effects of hydrothermal pretreatment of Napier grass, a model lignocellulosic biomass, on methane yield were examined through series of batch and semi-continuous studies. In batch studies, the highest methane yield of 248.2 ± 5.5 NmL CH4/g volatile solids (VS)added was obtained from the biomass pretreated at 175 °C, which was 35% higher than that from the unpretreated biomass. The biomass pretreated at 200 °C resulted in formation of 5-hydroxymethylfurfural and furfural, which significantly inhibited methanogenesis. In semi-continuous studies, digester fed with the biomass pretreated at 200 °C at organic loading rate (OLR) of 4 g VS/L.d resulted in digester failure. Thus, OLRsoluble/OLRtotal ratio

Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical-chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48-77%) in the removal of antibiotics. In this review, we systematically summarize the behavior and removal of different antibiotics in various biological treatment systems with discussion on their removal efficiency, removal mechanisms, critical bioreactor operating conditions affecting antibiotics removal, and recent innovative advancements. Besides, relevant background information including antibiotics classification, physical-chemical properties, and their occurrence in the environment from different sources is also briefly covered. This review aims to advance our understanding of the fate of various classes of antibiotics in engineered biological wastewater treatment systems and outlines future research directions.

Anaerobic digestion (AD) is a matured technology for waste (water) remediation/stabilization and bioenergy generation in the form of biogas. AD technology has several inherent benefits ranging from generating renewable energy, remediating waste (water), and reducing greenhouse gas emission to improving health/hygiene and the overall socio-economic status of rural communities in developing nations. In recent years, there has been a paradigm shift in applications of AD technology beyond biogas. This special issue (SI) entitled, “Anaerobic Digestion Beyond Biogas (ADBB-2021),” was conceptualized to incorporate some of the recent advances in AD in which the emphasis is beyond biogas, such as anaerobic biorefinery, chain elongation, treatment of micropollutants, toxicity and system stability, digestate as biofertilizer, bio-electrochemical systems, innovative bioreactors, carbon sequestration, biogas upgrading, microbiomes, waste (water) remediation, residues/waste pre-treatment, promoter addition, and modeling, process control, and automation, among others. This VSI: ADBB-2021 contains 53 manuscripts (14 critical reviews and 39 research). The key findings of each manuscript are briefly summarized here, which can serve as a valuable resource for AD researchers to learn of major advances in AD technology and identify future research directions.

Nanobubble technology has significant potential to improve the anaerobic digestion (AD) process by ameliorating the rate-limiting steps of hydrolysis and methanogenesis, as well as providing process stability by reducing sulfide and volatile fatty acid (VFA) levels. Nanobubbles (NB) can enhance substrate accessibility, digestibility, and enzymatic activity due to their minuscule size, high electrostatic interaction, and ability to generate reactive oxygen species. Air- and O2-NB can create a microaerobic environment for higher efficiency of the electron transport system, thereby reducing VFAs through enhanced facultative bacterial activity. Additionally, H2- and CO2-NB can improve hydrogenotrophic methanogenesis. Recently, several studies have employed NB technology in the AD process. There is, however, a lack of concise, synthesized information on NB applications to the AD process. This review provides an in-depth discussion on the NB-integrated AD process and the putative mechanisms involved. General discussions on other potential applications and future research directions are also provided.

Azo dye is the most versatile class of dyes used in the textile industry. Although the sulfidogenic process shows superiority in the removal of azo dye, the role of biogenic sulfide produced by sulfate-reducing bacteria (SRB) in the decolorization of azo dye is unclear. This study explored the mechanism of biogenic sulfide for removal of a model azo dye (Direct Red 81 (DR 81)) through biotic and abiotic batch tests with analysis of intermediates of the azo dye degradation. The results showed that biogenic sulfide produced from sulfate reduction directly cleaved two groups of azo bond (-N N-), thereby achieving decolorization. Moreover, the decolorization rate was enhanced by nearly 3-fold (up to 42 ± 1 mg/L-hr; removal efficiency > 99%) by adding an external carbon source or elevating the initial azo dye concentration. This study showed that biogenic sulfide plays an essential role in azo dye decolorization and provides a new avenue for the potential application of biogenic sulfide from the sulfidogenic system for the treatment of azo dye-laden wastewater.

Intermittent (every other day) microaerobic [picomolar oxygen by oxidation-reduction potential (ORP) set at +25 mV above anaerobic baseline] digestion of lignocellulosic biomass showed higher digestibility and better stability at a high organic loading rate (OLR) of 5 g volatile solids (VS)/L/d than that under strict anaerobic conditions. However, the microbial mechanisms supporting the delicate balance under microaeration remain underexplored. On the basis of our previous findings that microbial communities in replicate experiments were dominated by strains of the genus Proteiniphilum but contained diverse taxa of methanogenic archaea, here we recovered related genomes and reconstructed the putative metabolic pathways using a genome-centric metagenomic approach. The highly enriched Proteiniphilum strains were identified as efficient cellulolytic facultative bacterium, which directly degraded lignocellulose to carbon dioxide, formate, and acetate via aerobic respiration and anaerobic fermentation, alternatively. Moreover, high oxygen affinity cytochromes, bd-type terminal oxidases, in Proteiniphilum strains were found to be closely associated with such picomolar oxygen conditions, which has long been overlooked in anaerobic digestion. Furthermore, hydrogenotrophic methanogenesis was the prevalent pathway for methane production while Methanosarcina, Methanobrevibacter, and Methanocorpusculum were the dominant methanogens in the replicate experiments. Importantly, the two functional groups, namely cellulolytic facultative Proteiniphilum strains and methanogens, encoded various antioxidant enzymes. Energy-dependent reactive oxygen species (ROS) scavengers (superoxide reductase (SOR) and rubrerythrin (rbr) were ubiquitously present in different methanogenic taxa in response to replicate-specific ORP levels (-470, -450 and -475 mV). Collectively, cytochrome bd oxidase and ROS defenders may play roles in improving the digestibility and stability observed in intermittent microaerobic digestion.

Ibuprofen (IBU) is one of the frequently detected non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater treatment plants (WWTPs) and aquatic environment. However, little is known about the effect of IBU and its biotransformation products (TPs) on different biological sludge systems and aquatic environment. The effects and toxicity of IBU and TPs on three biological sludge systems (i.e., activated sludge (AS), sulfate-reducing bacteria (SRB)-enriched sludge and anaerobic methanogenic (AnM) sludge systems) and aquatic environment were comprehensively evaluated through a long-term operation of three bioreactors and a series of batch experiments. Both of the SRB-enriched sludge and AnM sludge systems were not affected under a long-term exposure to IBU, based on removing organic carbon and sulfur and producing methane. This could be attributed to the high tolerance of functional microbes in the SRB-enriched sludge (e.g., genus Desulfobacter) and AnM sludge systems (e.g., genus Candidatus Methanomethylicus) for IBU. In contrast, IBU had some apparently inhibitory effects on the AS system, such as reduced organic removal efficiency and poor sludge settling. The analysis on microbial community revealed that IBU significantly inhibited the genera involved in organic degradation (e.g., genus Candidatus Competibacter) and also stimulated those genera (e.g., genus Brachymonas) to secret excess extracellular polymeric substances (EPS), which thus caused sludge bulking in the AS system. The toxicity of IBU and its TPs in the effluent of the AS system was also investigated with Vibrio fischeri bioluminescence inhibition tests and quantitative structure activity relationship (QSAR) analysis by ecological structure-activity relationship (ECOSAR) program. The results indicated that the AS system could effectively eliminate the acute toxicity of both IBU and TPs, but a potential chronic toxicity of IBU could still existed, which could be more harmful to aquatic organisms than that of its TPs. These findings provide an insight into the toxic effects of IBU and its TPs on biological sludge systems and ecosystem.

Population growth and unprecedented economic growth and urbanization, especially in low- and middle-income countries, coupled with extreme weather patterns, the high-environmental footprint of agricultural practices, and disposal-oriented waste management practices, require significant changes in the ways we produce food, feed and fuel, and manage enormous amounts of organic wastes. Farming insects such as the black soldier fly (BSF) (Hermetia illucens) on diverse organic wastes provides an opportunity for producing nutrient-rich animal feed, fuel, organic fertilizer, and biobased products with concurrent valorization of wastes. Inclusion of BSF larvae/pupae in the diets of poultry, fish, and swine has shown promise as a potential substitute of conventional feed ingredients such as soybean meal and fish meal. Moreover, the bioactive compounds such as antimicrobial peptides, medium chain fatty acids, and chitin and its derivatives present in BSF larvae/pupae, could also add values to the animal diets. However, to realize the full potential of BSF-based biorefining, more research and development efforts are necessary for scaling up the production and processing of BSF biomass using more mechanized and automated systems. More studies are also needed to ensure the safety of the BSF biomass grown on various organic wastes for animal feed (also food) and legalizing the feed application of BSF biomass to wider categories of animals. This critical review presents the current status of the BSF technology, identifies the research gaps, highlights the challenges towards industrial scale production, and provides future perspectives.

Exposure of a small amount of oxygen/air (microaeration) has been reported to benefit the anaerobic digestion (AD) process in enhancing hydrolysis, improving methane yield, stabilizing the process and scavenging hydrogen sulfide among others. The underlying mechanism of enhancing AD process via microaeration is the augmentation of activity and diversity of the microbial consortia that promotes syntrophic interactions among different microbial groups, thereby creating a more stable process. To design and implement a microaeration-based AD process, fundamental insights about the mechanism of the AD system at process, microbial and molecular levels must be fully explored. This review critically examines microaeration-based AD processes through our recent understandings of the effect of oxygen on microbial community structure, enzymatic, energetic, physiological, and biochemical aspects of the microbial-mediated process. Syntrophic interactions between hydrolytic, fermentative, sulfate reducing, syntrophic bacteria and methanogens under microaerobic conditions are examined to reveal putative mechanism and factors that need to be considered when implementing microaeration in AD process. Further studies are needed to better understand the microbial pathways and bioenergetics of the microaerobic AD process by adopting advanced molecular techniques such as metagenomics, transcriptomics, and proteomics.

Coke oven gas is considered as a potential hydrogen source for biogas bio-upgrading. In this study, the effects of CO on biomethanation performance and microbial community structure of hydrogenotrophic mixed cultures were investigated under thermophilic (55 °C) and extreme-thermophilic (70 °C) conditions. 5% (v/v) CO did not inhibit hydrogenotrophic methanogenesis during semi-continuous operation, and 83–97% CO conversion to CH4 was achieved. Methanothermobacter thermoautotrophicus was the dominant methanogen at both temperatures and was the main functional archaea associated with CO biomethanation. Specific methanogenic activity test results showed that long-term 5% CO acclimation shortened the lag phase from 5 h to 1 h at 55 °C and 15 h to 3 h at 70 °C. CO2 was the preferred carbon source over CO for hydrogenotrophic methanogens and CO consumption only started when CO2 was completely depleted. M. thermoautotrophicus dominated mixed cultures showed a great potential in simultaneous hydrogenotrophic methanogenesis and CO biomethanation.

In this study, hydrogenotrophic methanogenesis with respect to methanogenic activity and microbial structures under extreme-thermophilic conditions were examined, and compared with the conventional thermophilic condition. The hydrogenotrophic methanogens were successfully acclimated to the temperatures of 55, 65 and 70 °C. Although acclimation was slower at 65 and 70 °C, hydrogenotrophic methanogenesis remained fairly stable. High-throughput sequencing using 16S rRNA analysis showed that the higher temperatures resulted in single archaea community dominated by hydrogenotrophic Methanothermobacter. Moreover, the syntrophic bacteria changed from Coprothermobacter and Thermodesulfovibrio at 55 °C to Thermodesulfovibrio at 70 °C. Specific hydrogenotrophic methanogenic rate at 70 °C was 98.6 ± 4.2 Nml CH4/g VS/hr, which was over 4-folds higher than that 8at 55 °C. The lag phase under extreme-thermophilic conditions was longer than thermophilic condition, which was probably due to the archaeal structure with low diversity. Extreme-thermophilic condition resulted in a shift in methanogenesis pathway from acetoclastic methanogenesis to hydrogenotrophic methanogenesis with the enrichment of Methanothermobacter thermautotrophicus.

Aquaponics recycles nitrogen from nitrogen-rich aquaculture effluent into organic crops (fish and vegetables/fruits) in hydroponic grow beds. Fundamental understanding of nitrogen transformations in aquaponics is critically important to improve nitrogen use efficiency (NUE) within aquaponics systems and to reduce release of environmentally harmful effluent and gases. This study elucidated nitrogen transformations in floating-raft aquaponic systems using four plant species, namely lettuce (Lactuca sativa longifolia cv. Jericho), pak choi (Brassica rapa L. Chinensis), tomato (Lycopersicum esculentum), and chive (Allium schoenoprasum L.). Using nitrogen mass balance and 15N labeled nitrogen species, it was found that nitrate was the primary form of nitrogen assimilated by plants. Nitrification and denitrification occurred simultaneously in the aquaponic system, resulting in an inevitable nitrogen loss (22.3–29.3% of nitrogen input). Nitrogen loss via nitrifier denitrification (33.7–55.3%), which was stimulated by low dissolved oxygen (DO) levels (∼3.8 mg/L), and denitrification occurred simultaneously. Moreover, nitrogen loss from the aquaponic system in the form of nitrous oxide (N2O), a potent greenhouse gas, accounted up to 0.72–1.03% of the nitrogen input. Aerating biofilters to prevent the formation of anoxic zones reduced total nitrogen loss but did not affect N2O emission. This study suggests that increasing DO concentrations only by aeration does not improve NUE and reduce N2O emission simultaneously.

Aquaponics is a technology for food production (fish and vegetables/fruits) with concomitant remediation of nitrogen-rich aquaculture effluent. There is, however, a critical need to improve the nitrogen use efficiency (NUE) in aquaponics. Here, we employed quantitative polymerase chain reactions and next-generation sequencing to evaluate the bacterial communities and their links to nitrogen transformations for improving NUEs in four bench-scale plant-based floating-raft aquaponics (pak choi, lettuce, chive, and tomato) and three pH levels (7.0, 6.0, and 5.2). Low relative abundance of nitrifiers in plant roots and biofilters suggested nitrogen loss, which decreased NUE in aquaponics. Low pH level was a major factor that shifted the microbial communities and reduced the relative abundance of nitrifiers in aquaponic systems, leading to total ammonia nitrogen accumulation in recirculating water. In plant roots, the abundance of nitrite-oxidizing bacteria (e.g., Nitrospira spp.) did not decrease at low pH levels, suggesting the benefit of growing plants in aquaponics for efficient nitrification and improving NUE. These findings on microbial communities and nitrogen transformations provided complementary strategies to improve the performance of the aquaponics regarding water quality and extent of nutrient recovery from aquaculture effluent.

Extracellular polymeric substances (EPS) of microbial sludge play a crucial role in removal of organic micropollutants during biological wastewater treatment. In this study, we examined ciprofloxacin (CIP) removal in three parallel bench-scale reactors using aerobic sludge (AS), anaerobic sludge (AnS), and sulfate-reducing bacteria (SRB) sludge. The results showed that the SRB sludge had the highest specific CIP removal rate via adsorption and biodegradation. CIP removal by EPS accounted up to 35. 6 ± 1.4%, 23.7 ± 0.6%, and 25.5 ± 0.4% of total removal in AS, AnS, and SRB sludge systems, respectively, at influent CIP concentration of 1000 μg/L, which implied that EPS played a critical role in CIP removal. The binding mechanism of EPS on CIP adsorption in three sludge systems were further investigated using a series of batch tests. The results suggested that EPS of SRB sludge possessed stronger hydrophobicity (proteins/polysaccharides (PN/PS) ratio), higher availability of adsorption sites (binding sites ( n)), and higher binding strength (binding constant ( K

Anaerobic digestion (AD) of lignocellulosic biomass i.e. Napier grass (Pennisetum purpureum), was investigated via a series of batch and bench-scale experiments. Two semi-continuous bench-scale horizontal bioreactors were operated in parallel for nearly 300 days, and the reactors were able to handle the organic loading rate (OLR) up to 6 kg volatile solids (VS)/m3-d, which was among the highest OLR reported in the literature for lignocellulosic biomass. Hemicellulose was the main structural carbohydrate of lignocellulosic biomass per unit respective mass (dry weight) basis contributing to methane production. The cellulose- and lignin-rich digestate was further examined for its bioenergy potential via torrefaction and hydrothermal carbonization, and was found to have higher mass and energy yield compared with those of raw Napier grass. The produced solid char has energy content similar to bituminous coal with low ash content. Thus, this study provided a successful integration of anaerobic digestion with thermochemical conversion representing a biorefinery concept for lignocellulosic feedstocks.

Growing consumption of fossil reserves to meet the rising demand of energy has led to climate deterioration and simultaneous waste generation, urging modern society to find sustainable energy resource that can meet the growing energy demands and reduce greenhouse gas emissions and carbon footprints. In this aspect, hydrogen (H2) is one of the most promising sustainable clean fuels that has gained significant interest in recent years. This article highlights the major research progress on biohydrogen production from renewable bioresources such as organic wastes, lignocellulosic biomass, algal biomass, and industrial wastewaters. It summarizes the research highlights of manuscripts published in the special issue (VSI: ReBioH2-2020), which contains twenty-two articles, including seven critical reviews and fifteen research articles, focusing on biotechnological and thermochemical routes for biohydrogen production from renewable feedstocks. The major findings of the research works in this special issue can be used as a road-map for sustainable renewable hydrogen production from bioresources.

Recently, anaerobic self-forming dynamic membrane bioreactors (AnSFDMBRs) have attracted increasing attention, and are considered as an alternative to conventional anaerobic membrane bioreactors (AnMBRs). The key advantages of AnSFDMBRs include high flux, low propensity towards fouling, and low capital and operational costs. Although there have been several reviews on AnMBRs, very few reviews on AnSFDMBR system. Previous AnSFDMBR studies have focused on lab-scale to investigate the long-term flux, methods to improve performance and the associated mechanisms. Microbial analysis showed that the phyla namely Proteobacteria, Bacteroidetes and Firmicutes are dominant in both bulk sludge and cake biofilm, but their abundance is low in biocake. This review critically examines the fundamentals of AnSFDMBRs, operational conditions, process optimization and applications. Moreover, the current knowledge gaps (e.g., dynamic membrane module optimization, membrane surface modification and functional microbes enrichment) that should be studied in future to design an efficient AnSFDMBR system for treatment of diverse wastewaters.

Lignocellulosic biomass is the most abundant renewable bioresource on earth. In lignocellulosic biomass, the cellulose and hemicellulose are bound with lignin and other molecules to form a complex structure not easily accessible to microbial degradation. Anaerobic digestion (AD) of lignocellulosic biomass with a focus on improving hydrolysis, the rate limiting step in AD of lignocellulosic feedstocks, has received considerable attention. This review highlights challenges with AD of lignocellulosic biomass, factors contributing to its recalcitrance, and natural microbial ecosystems, such as the gastrointestinal tracts of herbivorous animals, capable of performing hydrolysis efficiently. Biological strategies that have been evaluated to enhance hydrolysis of lignocellulosic biomass include biological pretreatment, co-digestion, and inoculum selection. Strategies to further improve these approaches along with future research directions are outlined with a focus on linking studies of microbial communities involved in hydrolysis of lignocellulosics to process engineering.

Nitrogen is a key nutrient for fish and vegetable productions in aquaponic systems. However, the fate of nitrogen in aquaponic systems has not been fully understood, leading to difficulty in optimizing nitrogen use efficiency (NUE) and plant production. In this study, the fate of nitrogen in floating-raft aquaponic systems with two plant species, pak choi ( Brassica rapa L. chinensis ) and lettuce ( Lactuca sativa longifolia cv. Jericho ), and tilapia ( Oreochromis sp.) was evaluated using mass balance and natural abundance nitrogen isotopic compositions. Dissolved oxygen (DO) levels associated with hydraulic loading rate (HLR) were found to positively affect nitrite oxidation rate. Increase in nitrite concentration was observed in recirculating water under low DO levels. Nitrite is an intermediate in the dissimilatory reduction of nitrate to N 2 gas. Based on progressive enrichment of 15 N of nitrate with time in the recirculating water, we estimated total nitrogen loss of up to 46.3% via denitrification. Nitrogen loss via denitrification was reduced by 44–56% when the feed-to-plant ratio was decreased by 30%. Results of this study provide better understanding of nitrogen transformations, which could help in designing and operating efficient aquaponic systems.

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200–2000 mg SO 4 2 - / L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5 g chemical oxygen demand (COD)/L·day and a hydraulic retention time (HRT) of 20 days. The biochar was able to remove about 98.0 (±1.2)% of H2S for the ranges of concentrations from 105–1020 ppmv, especially at high moisture content (80–85%). Very high H2S adsorption capacity (up to 273.2 ± 1.9 mg H2S/g) of biochar is expected to enhance the H2S oxidation into S0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils.

In recent years, aquaponic systems have gained significant popularity as soilless agriculture systems for organic fruits and vegetables production with concomitant remediation of aquaculture effluent. Aquaponics is a potential sustainable food production system that integrates aquaculture with hydroponics in which nitrogen-rich effluent from the fish production is utilized for plant growth. Because nitrogen is one of the most important inputs in an aquaponic system, it is critical to investigate the nitrogen transformations in the system for enhanced recovery of resources. Since studies on nitrogen transformations and nitrogen utilization efficiency (NUE) in aquaponic systems have been very limited, this review critically examines the important fates of nitrogen from input to outputs (e.g., ammonia nitrogen generation, nitrification, nitrate assimilation and nitrogen loss) to improve NUE in aquaponic systems. Various factors affecting the nitrogen transformations are also discussed. Furthermore, an example of nitrogen imbalance between nitrate uptake and nitrate generation rates in an aquaponic system was demonstrated. This review aims to advance our current understanding of nitrogen transformations and outlines future research needs in aquaponic systems, a sustainable model for efficient water and nutrient managements, and food production.

Experimental conditions of liquid hot water (LHW) pretreatment were tested for two dedicated energy crops, Napiergrass (Pennisetum purpureum) and Energycane (Saccharum officinarum × Saccharum robustum). Both crops showed differential resistance to temperature during pretreatment and differences in response to biomass and enzyme loadings during subsequent enzymatic hydrolysis. Sugar response surfaces, for both glucose release per g pretreated biomass and as percent yield of glucose present in the initial biomass, were estimated using a General Additive Model (GAM) in R to compare non-linear sugar release as temperature, and biomass and enzyme loadings were manipulated. Compared to Napiergrass, more structural glucose is estimated to be recovered from Energycane per g of pretreated biomass under relatively less harsh pretreatment conditions, however, Napiergrass had the highest measured glucose yield. Sugar degradation products (furfural and hydroxymethylfurfural), pH, and biomass recovery differed significantly between crops across pretreatment temperatures, which could adversely affect downstream biochemical processes.

The potential for microbial protein production in the mixture of yellow wine lees and rice soaking wastewater was examined. Strong symbiotic effect was observed in fermentation with yeast-fungus mixed culture of Candida utilis and Geochichum candidum at a ratio of 1:1 (v/v). The maximum specific biomass yield of 4.91 ± 0.48 g final biomass/g initial biomass with a protein content of 68.5 ± 1.0% was achieved at inoculum-to-substrate ratio of 10% (v/v) and aeration rate of 1.0 volumeair/volumeliquid/min. The essential amino acids contents of the derived protein were comparable to commercial protein sources with high amounts of methionine (2.87%, based on total protein). The reduction in soluble chemical oxygen demand of 79.4 ± 0.4% was mainly due to uptake of carbohydrate, soluble protein, volatile fatty acids, amino acids, etc. The application of mixed yeast-fungus technology provides a new opportunity for microbial protein production from these low-value organic residue streams.

Ibuprofen (IBU), a common non-steroidal anti-inflammatory drug (NSAID), is widely used by humans for controlling fever and pain, and is frequently detected in the influent of wastewater treatment plants and different aquatic environments. In this study, the biotransformation of IBU in activated sludge (AS), anaerobic methanogenic sludge (AnMS) and sulfate-reducing bacteria (SRB)-enriched sludge systems was investigated at three different concentrations of 100, 500 and 1000 μg/L via a series of batch and continuous studies. IBU at concentration of 100 μg/L was effectively biodegraded by AS whereas AnMS and SRB-enriched sludge were less effective in IBU biodegradation at all concentrations tested. However, at higher IBU concentrations of 500 and 1000 μg/L, AS showed poor IBU biodegradation and chemical oxygen demand (COD) removal due to inhibition of aerobic heterotrophic bacteria (i.e., Candidatus Competibacter) by IBU and/or IBU biotransformation products. The microbial analyses showed that IBU addition shifted the microbial community structure in AS, AnMS and SRB-enriched sludge systems, however, the removals of COD, nitrogen and sulfur in both anaerobic sludge systems were not affected significantly (p > 0.05). The findings of this study provided a new insight into biotransformation of IBU in three important biological sludge systems.

This study developed an intermittent oxidation-reduction potential (ORP)-controlled micro-aeration system for high solids anaerobic digestion (AD) of lignocellulosic biomass without volatile fatty acids (VFA) accumulation at high organic loading rate (OLR). Traditional AD of Napier grass, a model lignocellulosic biomass, at an OLR of 5 g volatile solids (VS)/L/day resulted in an accumulation of total VFA concentration up to 9.2 g/L as acetic acid (HAc) equivalent, causing rapid drops in pH and methane yield, and driving the digester to the verge of failure. Once intermittent (every 24 h) ORP-controlled micro-aeration (at ORP of −470 mV) was initiated, the total VFA concentration rapidly decreased to 3.0 g HAc/L and the methane yield improved, resulting in stable digester performance without the need for alkalinity supplementation or OLR reduction. By combining reactor performance results, mass balance analyses, microbial community characterization data, and a bioenergetic evaluation, this study suggested that rapid VFA conversion and CH4 production were carried out by facultative anaerobes and hydrogenotrophic methanogens under micro-aerobic conditions. This novel operating approach can be applied as an effective control strategy for high OLR AD processes especially in the event of VFA accumulation.

This study investigated sulfamethoxazole (SMX) removal and fate in sulfate-reducing up-flow sludge bed (SRUSB) reactors inoculated with sulfate-reducing bacteria (SRB) granules and flocs. The resilience of SRB granules and flocs against varying pHs and hydraulic retention times (HRTs) was also examined. SRB granules and flocs efficiently removed SMX from wastewater, which was significantly higher than the aerobic sludge. SRB granules achieved significantly (p

The pyrolysis kinetics of sewage sludge was studied to determine the constituent of sludge and explore the feasibility of pyrolytic post-treatment. Both flocculent sludge and granular sludge were pyrolysed in a thermogravimetric analyser under inert atmospheric conditions. The pyrolysis of granular sludge and flocculent sludge were described by three parallel reactions model with three individual pseudo-components. The decomposition activation energy values of the three pseudo-components were determined by iso-conversional methods to be 263.97 kJ/mol, 257.18 kJ/mol and 153.61 kJ/mol in flocculent sludge and 139.89 kJ/mol, 228.78 kJ/mol and 142.78 kJ/mol in granular sludge, respectively. Granular sludge exhibited better thermal stability but lower devolatilisation activation energy than flocculent sludge, which could be attributed by enriched alkali and alkaline metals during granulation. Master plots of experimental data sets suggested that the decomposition of all organic pseudo-components of flocculent sludge followed the nth-order mechanism while the pyrolytic mechanism of the first organic fraction in granular sludge coincided with random nucleation and nuclei growth. By investigating the pyrolytic behaviour, this study sheds light on the composition of granular sludge and the impact of sludge components on granular sludge pyrolysis, and lays the foundation for the treatment of waste granular sludge with potential for resource and energy recovery in the near future.

Anaerobic digestion is a long-established technology for the valorization of diverse organic wastes with concomitant generation of valuable resources. However, mono-digestion (i.e., anaerobic digestion using one feedstock) suffers from challenges associated with feedstock characteristics. Co-digestion using multiple feedstocks provides the potential to overcome these limitations. Significant research and development efforts have highlighted several inherent merits of co-digestion, including enhanced digestibility due to synergistic effects of co-substrates, better process stability, and higher nutrient value of the produced co-digestate. However, studies focused on the underlying effects of diverse co-feedstocks on digester performance and stability have not been synthesized so far. This review fills this gap by highlighting the limitations of mono-digestion and critically examining the benefits of co-digestion. Furthermore, this review discusses synergistic effect of co-substrates, characterization of microbial communities, the prediction of biogas production via different kinetic models, and highlights future research directions for the development of a sustainable biorefinery.

The efficacy of C4 grasses as feedstocks for liquid fuel production and their climate mitigation potential remain unresolved in the tropics. To identify highly convertible C4 grasses, we measured final fuels and postprocess biomass produced in two laboratory-scale conversion pathways across 12 species and varieties within the Poaceae (grass) family. Total mass, carbon, and energy in final fuels and postprocess biomass were assessed based on field mass and area-based production. Two lignocellulosic processes were investigated: (1) anaerobic digestion (AD) to methane and (2) hot water pretreatment and enzymatic hydrolysis (HWP-EH) to ethanol. We found AD converted lignocellulose to methane more efficiently in terms of carbon and energy compared to ethanol production using HWP-EH, although improvements to and the optimization of each process could change these contrasts. The resulting data provide design limitations for agricultural production and biorefinery systems that regulate these systems as net carbon sources or sinks to the atmosphere. Median carbon recovery in final fuels and postprocess biomass from the studied C4 grasses were ~5 Mg C ha−1 year−1 for both methane and ethanol, while median energy recovery was ~200 MJ ha−1 year−1 for ethanol and ~275 MJ ha−1 year−1 for methane. The highest carbon and energy recovery from lignocellulose was achieved during methane production from a sugarcane hybrid called energycane, with ~10 Mg C ha−1 year−1 and ~450 MJ ha−1 year−1 of carbon and energy recovered, respectively, from fuels and post-process biomass combined. Carbon and energy recovery during ethanol production was also highest for energycane, with ~9 Mg C ha−1 year−1 and ~350 MJ ha−1 year−1 of carbon and energy recovered in fuels and postprocess biomass combined. Although several process streams remain unresolved, agricultural production and conversion of C4 grasses must operate within these carbon and energy limitations for biofuel and bioenergy production to be an atmospheric carbon sink.

Anaerobic digestion of organic wastes produces solid residues known as digestates, which have potential as a fertilizer and soil amendment. The majority of research on digestate focuses on their fertilizer value. However, there is a lack of information about additional effects they may have on plant growth, both positive and negative. Understanding the effects of digestate on plant growth is essential to optimizing their use in agriculture and helping close the loop of material and energy balances. This greenhouse study evaluated the effects of two different digestates, a food waste digestate (FWD) and a lignocellulosic biomass digestate (LBD), a liquid fertilizer, and various combinations of fertilizer and digestates on plant growth, nutrient uptake and nutrient use efficiency (NUE) of Brassica juncea (kai choy) plants. It also evaluated potential negative attributes of the digestates, including salinity and possible biohazards. Combinations of LBD and fertilizer performed as well or slightly better than the fertilizer control for most parameters, including aboveground biomass and root length. These same combinations had significantly higher nitrogen use efficiency than the fertilizer control. Inhibitory effects were observed in 100% LBD treatments, likely due to the high electrical conductivity of the media from digestate application. Based on this research, LBD could partially replace mineral fertilizers for kai choy at up to 50% of the target nitrogen rate and may lead to increased plant growth beyond mineral fertilizers. FWD could replace up to 100% of the target nitrogen application, without causing significant negative effects on plant growth. Increasing the use of digestates in agriculture will provide additional incentives for the anaerobic digestion process, as it produces two valuable products: biogas for energy and digestate for fertilizer.

Ciprofloxacin (CIP), one of the most widely used fluoroquinolone antibiotics, is frequently detected in the effluents of wastewater treatment plants and aquatic environments. In this study, a CIP-degrading bacterial strain was isolated from the sulfate reducing bacteria (SRB)-enriched sludge, identified as Paraclostridium sp. (i.e., strain S2). The effects of critical operational parameters on CIP removal by the strain S2 were systematically studied and these parameters were optimized via response surface methodology to maximize CIP removal. Furthermore, the pathway and kinetics of CIP removal were investigated by varying the initial CIP concentrations (from 0.1 to 20 mg/L). The CIP removal was characterized by rapid sorption followed by biotransformation with a specific biotransformation rate of 1975.7 ± 109.1 µg/g-cell dry weight/h at an initial CIP concentration of 20 mg/L. Based on the main transformation products, several biotransformation pathways have been proposed including piperazine ring cleavage, OH/F substitution, decarboxylation, and hydroxylation as the major transformation reactions catalyzed by cytochrome P450 and dehydrogenases. Acute toxicity assessment apparently shows that CIP biotransformation by strain S2 resulted in the formation of less toxic intermediates. To the best of our knowledge, this is the very first study in which a key functional microbe, Paraclostridium sp., highly effective in CIP biotransformation, was isolated from SRB-enriched sludge. The findings of this study could facilitate in developing appropriate bioaugmentation strategy, and in designing and operating an SRB-based engineered process for treating CIP-laden wastewater.

Sulfur-driven autotrophic denitrification (SdAD) represents an effective alternative to heterotrophic denitrification process for the treatment of organic carbon deficient or organic carbon free water and wastewater streams. The electron supply by oxidation of sulfur substrates (i.e., total dissolved sulfide (TDS) and chemical elemental sulfur (S0chem)) and the electron distribution among nitrogen oxide reductases determines the denitrification rate, reduction and accumulation of intermediates (e.g., nitrite and nitrous oxide). In this study, the electron distribution (supply and consumption) in SdAD process was investigated through a series of batch experiments under electron donor and acceptor non-limiting and limiting feeding conditions. The electron distribution was significantly affected by sulfide loading rate, and the electron competition among nitrogen oxide reductases was intensified with the most electrons flowing towards nitrate reductase (Nar), and the least electrons towards nitrous oxide reductase (Nos) under decreased sulfide loading rate. The intensification of electron competition associated with unbalanced electron supply and consumption rates is more directly responsible for intermediates accumulation in SdAD process. Compared to S0chem, TDS was the preferable electron donor as it resulted in the lowest accumulation of denitrifying intermediates in SdAD process. The findings of this study not only improve the understanding of underlying mechanisms of electron distribution and accumulation of denitrifying intermediates in SdAD process, but also form a basis for selection of ideal electron donor and feeding conditions in applying SdAD process for remediation of water, wastewater and gaseous streams containing nitrogen and/or sulfide.

Approximately one-third of all food produced for human consumption worldwide is wasted. The current waste management practices are not only costly but also have adverse impact on environment. In this study, black soldier fly (BSF) (Hermetia illucens) larvae were grown on food wastes to produce fat and protein-rich BSF prepupae as a novel strategy for efficient organic waste management. The lipid content in BSF prepupae was characterized for fatty acids profile. Whole BSF prepupae, pressed cake, and meal were analyzed for important animal feed characteristics. BSF-derived oil has high concentration of medium chain saturated fatty acids (67% total fatty acids) and low concentration of polyunsaturated fatty acids (13% total fatty acids), which makes it potentially an ideal substrate for producing high quality biodiesel. BSF (prepupae, pressed cake, and meal) has feed value comparable to commercial feed sources. Thus, the bioconversion of organic waste into BSF prepupae has significant potential in generating high-value products with simultaneous waste valorization.

Sulfur-oxidizing bacteria (SOB) was successfully employed for effective autotrophic denitrification and sludge minimization in a full-scale application of saline sewage treatment in Hong Kong. In this study, a Granular Sludge Autotrophic Denitrification (GSAD) reactor was continuously operated over 600 days for SOB granulation, and to evaluate the long-term stability of SOB granules, microbial communities and denitrification efficacy. Sludge granulation initiated within the first 40 days of start-up with an average particle size of 186.4 μm and sludge volume index (SVI5) of 40 mL/g in 5 min. The sludge granules continued to grow reaching a nearly uniform size of mean diameter 1380 ± 20 μm with SVI5 of 30 mL/g during 600 days of GSAD reactor operation at hydraulic retention time of 5 h and nitrate loading rate of 0.33 kg-N/m3/d. The GSAD reactor with SOB granular sludge achieved 93.7 ± 2.1% nitrogen and complete sulfide removal with low sludge yield of 0.15 g-volatile suspended solids (VSS)/g-N, and much lower nitrous oxide (N2O) emission than the heterotrophic denitrifying process. Microbial community analysis using fluorescence in situ hybridization (FISH) technique revealed that granules were enriched with SOB contributing to autotrophic denitrification. Furthermore, 16S rRNA analysis showed diverse autotrophic denitrification related genera, namely Thiobacillus (32.6%), Sulfurimonas (31.3%), and Arcobacter (0.01%), accounting for 63.9% of total operational taxonomic units at the generic level. No heterotrophic denitrification related genera were detected. The results from this study could provide useful design and operating conditions with respect to SOB sludge granulation and its subsequent application in a full-scale autotrophic denitrification in the Sulfate reduction-Autotrophic denitrification-Nitrification Integrated (SANI) process.

Cassava, an important food crop, has been extensively employed as raw materials for various agri-industries to produce starch, bioethanol and other biobased products/chemicals. These cassava-based industries also generate large quantities of wastes/residues, rich in organic matter and suspended solids, and pose significant environmental issues. Their complex biochemical composition with high organic content endows them with a great potential for bioconversion into value-added products via biorefinery thereby providing economic and environmental sustainability to cassava industries. This state-of-the-art review covers the source, composition and characteristics of cassava industrial wastes and residues, and their bioconversion into value-added products, mainly biofuels (ethanol and butanol), biogas, biosurfactant, organic acids and other valuable biochemicals among others. This paper also outlines future perspectives with respect to developing more effective and efficient bioconversion processes for converting the cassava wastes and residues into high-value products.

This study examined the use of biochar to alleviate sulfide toxicity to methane producing archaea (MPA) and sulfate-reducing bacteria (SRB) during anaerobic treatment of sulfate-rich wastewater with concomitant sulfur recovery. At the sulfate concentration of 6000 mg SO42−/L, the dissolved sulfide (DS) of 131 mg S/L resulted in total volatile fatty acids concentration of 3500 mg/L as acetic acid (HAc) and the reactors were on the verge of failure. Biochar removed >98% of H2S(g), 94% of DS, and 89% of unionized sulfide (H2Saq). 16S rRNA analysis revealed that after sulfide removal the relative abundance of MPA (Methanobacterium and Methanosaeta) increased from 0.7% to 3.7%, while the relative abundance of SRB (Desulfovibrio) decreased from 9.3% to 0.5% indicating that the reactor recovered to stable state. This study showed that biochar could effectively remove H2S from biogas, alleviate sulfide toxicity to MPA and SRB, and promote stability of the anaerobic process.

This study investigated the phosphorus adsorption behaviors of pristine and MgO modified biochars produced from woody biomass precursors (having different anatomical characteristics and similar specific gravities) and their MgCl2 impregnated counterparts. The biomass precursors were Longleaf pine wood shavings, Red Oak and Hard Maple sawdusts. The microstructural, physico-chemical, textural, and phosphorus adsorption characteristics of the pristine and MgO modified biochars were examined. The percent yields (45.01 – 56.35%) of the MgO modified biochars were higher than the percent yields (29.29 – 30.08%) of the pristine biochars, mainly due to the presence of added MgO. The pH of all the biochars showed that they were alkaline in nature. The cation exchange capacities of the pristine and MgO modified biochars were 1.62 – 3.20 cmol/kg and 84.81 – 111.12 cmol/kg, respectively. The specific surface areas of the pristine and MgO modified biochars were 0.26 - 8.82 m2/g and 22.02 - 28.07 m2/g, respectively. The phosphorus adsorption capacities of the pristine and MgO modified biochars were 1.88 – 2.78 mg/g and 28.20 – 29.22 mg/g, respectively. The pristine hardwood derived biochars (Hard Maple and Red Oak) showed better phosphorous adsorption capacities than the pristine softwood derived biochar (Longleaf Pine), and the MgO modified biochars showed 11 times higher phosphorus adsorption capacities than the pristine biochars.

This study examined the composition and anaerobic digestibility of the different plant parts of two high-yielding tropical energy crops, Energycane and Napier grass, collected across three locations and two seasons. Both biomass composition and biomethane yields varied significantly with crop types, plant parts and harvest seasons. In Energycane, specific methane yield (SMY) (Nm3 (kg VSadded)−1) was higher from stems (0.232 ± 0.003) than leaves (0.224 ± 0.003), while in Napier grass, SMY was higher from leaves (0.243 ± 0.002) than stems (0.168 ± 0.002). Energycane had higher specific and total (Nm3 ha−1 year−1) methane yields (0.230 ± 0.002 and 8749 ± 494, respectively) than Napier grass (0.192 ± 0.002 and 5575 ± 494, respectively). The SMYs from biomass correlated negatively with acid detergent fiber, cellulose and lignin content in the biomass. Energycane and Napier grass had lower specific but comparable total methane yields (TMYs) with maize. The ecological, economic and environmental merits associated with perennial crops suggest they could outperform maize as a substrate for bioenergy production.

Interaction of organic carbon, reduced sulphur and nitrate was examined using anaerobic baffled reactor for fresh leachate treatment by supplementing nitrate and/or sulphide to compartment 3. Nitrate was removed completely throughout the study mostly via denitrification (>80%) without nitrite accumulation. Besides carbon source, various reduced sulphur (e.g. sulphide, elemental sulphur and organic sulphur) could be involved in the nitrate reduction process via sulphur-based autotrophic denitrification when dissolved organic carbon/nitrate ratio decreased below 1.6. High sulphide concentration not only stimulated autotrophic denitrification, but it also inhibited heterotrophic denitrification, resulting in a shift (11–20%) from heterotrophic denitrification to dissimilatory nitrate reduction to ammonia. High-throughput 16S rRNA gene sequencing analysis further confirmed that sulphur-oxidizing nitrate-reducing bacteria were stimulated with increase in the proportion of bacterial population from 18.6% to 27.2% by high sulphide concentration, meanwhile, heterotrophic nitrate-reducing bacteria and fermentative bacteria were inhibited with 25.5% and 66.6% decrease in the bacterial population.

Ciprofloxacin (CIP), a fluoroquinolone antibiotic, removal was examined for the first time, in an anaerobic sulfate-reducing bacteria (SRB) sludge system. About 28.0% of CIP was biodegraded by SRB sludge when the influent CIP concentration was 5000 μg/L. Some SRB genera with high tolerance to CIP (i.e. Desulfobacter), were enriched at CIP concentration of 5000 μg/L. The changes in antibiotic resistance genes (ARGs) of SRB sludge coupled with CIP biodegradation intermediates were used to understand the mechanism of CIP biodegradation for the first time. The percentage of efflux pump genes associated with ARGs increased, while the percentage of fluoroquinolone resistance genes that inhibit the DNA copy of bacteria decreased during prolonged exposure to CIP. It implies that some intracellular CIP was extruded into extracellular environment of microbial cells via efflux pump genes to reduce fluoroquinolone resistance genes accumulation caused by exposure to CIP. Additionally, the degradation products and the possible pathways of CIP biodegradation were also examined using the new method developed in this study. The results suggest that CIP was biodegraded intracellularly via desethylation reaction in piperazinyl ring and hydroxylation reaction catalyzed by cytochrome P450 enzymes. This study provides an insight into the mechanism and pathways of CIP biodegradation by SRB sludge, and opens-up a new opportunity for the treatment of CIP-containing wastewater using sulfur-mediated biological process.

Autotrophic denitrification has been widely studied for odor mitigation, corrosion control and nitrogen removal in recent years. This paper examines the response of sulfur-oxidizing bacteria (SOB) driven autotrophic denitrification under short-term stress of dissolved sulfide. A series of batch tests were conducted to investigate the effect of different sulfide concentrations (0-1600 mg-total dissolved sulfide (TDS)/L) on autotrophic denitrification and sulfide oxidation by SOB-enriched sludge. Our results show that autotrophic denitrification (NO3- to N2) was stimulated up to 200 mg-TDS/L with a maximum denitrification rate of 9.4 mg-N/g-volatile suspended solids (VSS)/h, and the nitrite reduction was a rate limiting step. When sulfide concentration was higher than 200 mg-TDS/L, it inhibited nitrate reductase, and nitrate reduction became the rate limiting step according to Edwards and Aiba inhibition models. Sulfide oxidation, however, was not inhibited and the maximum rate of 100.3 mg-TDS/g-VSS/h was obtained at sulfide concentration of 1000 mg-TDS/L. It is important to point out that the transient inhibition on autotrophic denitrification caused by high sulfide stress was resilient and non-lethal with no significant changes in cell viability even under sulfide concentration of 1000 mg-TDS/L. This study reveals the stimulatory and inhibitory effects of dissolved sulfide on SOB driven autotrophic denitrification and its possible underlying mechanism with discussion on engineering implications.

With growing global interest in bioenergy, biobased product and environmental sustainability, the first International Conference on Bioresource Technology for Bioenergy, Bioproducts & Environmental Sustainability (BIORESTEC) was organized from October 2326, 2016 in Sitges, Barcelona in Spain. The conference was organized in association with Elseviers premier journal Bioresource Technology (BITE), with an aim to provide a shared forum for researchers, academicians, industries, and policymakers, to discuss the current state-of-the-art and the emerging trends in biotechnology, bioenergy, and biobased products. The 1st BIORESTEC conference received tremendous response from all over the globe with 754 abstracts submitted. The scientific committee consisted of 13 eminent scientists from 11 countries. The committee then screened and selected 54 abstracts for oral and 166 abtsracts for poster presentations. Besides, there were 19 invited speakers from 14 countries. Apart from the scientific presentations, a workshop on How to write a scientific paper and get published was also organized for early career researchers by Elsevier. This special issue of the journal contain 29 papers (all presented at the BIORESTEC conference) after peer-review process. These papers broadly cover areas such as biomass pretreatment, algal and lignocellulose biorefinery, biological waste treatment, white biotechnology and biomass policies, LCA and techno-economics and classified as below., info:eu-repo/semantics/publishedVersion

In recent years, there has been a significant interest on biochar for various environmental applications, e.g., pollutants removal, carbon sequestration, and soil amelioration. Biochar has several unique properties, which makes it an efficient, cost-effective and environmentally-friendly material for diverse contaminants removal. The variability in physicochemical properties (e.g., surface area, microporosity, and pH) provides an avenue for biochar to maximize its efficacy to targeted applications. This review aims to highlight the vital role of surface architecture of biochar in different environmental applications. Particularly, it provides a critical review of current research updates related to the pollutants interaction with surface functional groups of biochars and the effect of the parameters variability on biochar attributes pertinent to specific pollutants removal, involved mechanisms, and competence for these removals. Moreover, future research directions of biochar research are also discussed.

The anaerobic process has been widely adopted for the treatment of high-strength wastewater because of several inherent merits. This chapter provides an overview of bioreactor design and development, especially for the treatment of industrial effluents. Various considerations on the anaerobic treatment of industrial effluents are discussed. Strategies for decoupling solids retention time from hydraulic retention time are also presented. Various anaerobic reactor configurations and design and development are also presented. The chapter concludes with perspectives on where some of the research needs remain.

Adsorption plays an important role on ciprofloxacin (CIP) removal in biological wastewater treatment systems. In this study, mechanisms and thermodynamics of CIP adsorption by sulfate-reducing bacteria (SRB) sludge were examined via a series of batch studies. CIP adsorption by SRB sludge was a pH-dependent process and was strongly correlated with CIP speciation and SRB sludge properties via multiple adsorption mechanisms including electrostatic attraction, cation exchange and bridging, π-π interaction and hydrogen bond. The presence of cations such as Cu(II) and Fe(III) significantly improved the CIP adsorption onto SRB sludge via surface complexation (coordination and chelation) at neutral (7.0) and acidic (4.0) pH conditions. The functional groups C–O, C–O–C, N–H, O–H and COOH on SRB sludge surface provided binding sites for CIP adsorption via π-π interaction, hydrogen bond and surface complexation as evident from Fourier Transform Infrared (FTIR) spectroscopy analysis. The adsorption of CIP onto SRB sludge was a spontaneous, exothermic and linear adsorption process that included both physisorption and chemisorption. The findings of this study provided insights into the mechanisms and thermodynamics of CIP adsorption by SRB sludge, and have significant potential of applying SRB sludge system for the treatment of CIP-laden wastewaters.