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Aquaculture is the fastest growing agricultural sector in the world, and the annual aquaculture production reached 82 million tonnes in 2018. Fish feed is the most expensive component of aquaculture. The partial replacement of commercial fish feed with biofloc was evaluated as a dietary ingredient in feed for barramundi (Lates calcarifer), a high-value carnivorous fish. Biofloc was produced from the effluent of a recirculating aquaculture system under microaerophilic conditions, as part of its water treatment process, which was based on nutrient assimilation by microbial biomass. The biofloc was harvested and used in fish feed. The experimental feed was prepared by replacing 20% (w/w) of commercial barramundi feed with dry biofloc powder. Six 100 l plastic tanks were stocked with barramundi (average weight 27 ± 0.9 g) at a density of 20 kg/m3. The fish in three tanks were fed a commercial feed and the others with the experimental diet for 8 weeks, at 2% bodyweight per day. The fish were weighed weekly. At the end of the trial, the proximate body compositions and immune functions of the fish were analyzed. Fifteen fish from each treatment were challenged with Vibrio harveyi to examine their disease resistance. Weight gain was 14% higher (p < 0.05) in the control group compared to biofloc -fed group, but fish fed biofloc showed significantly higher survival rates after bacterial challenge (89% survival) compared to control (58% survival, p = 0.01). Sera of the biofloc -fed fish had higher levels of lysozyme and myeloperoxidase activity (p < 0.001). Similarly, the expression of immune-related genes in the kidneys was significantly higher in the biofloc -fed fish than in the control (p < 0.05). These results, together with an economic evaluation, demonstrate the potential practical application of biofloc as a feed ingredient in barramundi aquaculture. Further optimization of this practice is required.

Recovery of nutrients, such as ammonia, from wastewater offers an attractive approach to increase the overall sustainability of waste management practices. Conventional wastewater treatment processes require significant energy input, and the useful form of nitrogen (ammonia), is usually lost. Ammonia, a major component of fertilizers, is conventionally manufactured using the Haber–Bosch process, which accounts for approximately 2% of worldwide energy demand. A better approach would efficiently capture ammonia directly from the wastewater. In this study, ammonia is recovered directly by using an electrically conducting gas-stripping membrane that is immersed into a wastewater reactor. Under cathodic potentials, these membranes were used to facilitate conversion of ammonium (NH4+) into ammonia (NH3), which was then extracted by either circulating an acid solution or by applying a vacuum on the back side of the membrane. The mechanism involves water electrolysis, which generates OH−, and transforms ammonium to ammonia that is stripped through the membrane. By engineering the surface and transport properties of the membrane 68.8 ± 8.0 g N per m2 d−1 of ammonia was recovered, with an energy consumption of 7.1 ± 1.1 kW h kg−1 N.

Aquaponics is gaining renewed interest to enhance food security. This study aimed to investigate the performance of a novel off-grid aquaponics system with near-zero water and waste discharge, focusing on the carbon cycle and energy recovery that was achieved by the addition of onsite anaerobic treatment of the solid waste streams. Following a stabilization stage, the system was closely monitored for four months. Fish tank water was recirculated via solid and nitrification reactors, from which 66% was recycled to the fish tank directly and 34% indirectly through the hydroponically grown plants. Fish solid waste was anaerobically treated, energy was recovered, and the nutrient-rich supernatant was recycled to the plants to enhance production. Plant waste was also digested anaerobically for further recovery of energy and nutrients. Fish stocking density was 15.3 and over time reached approximately 40 kg/m3 where it was maintained. Feed (45% protein content) was applied daily at 2% of body weight. Typical fish performance was observed with a survival rate >97% and feed conversion ratio of 1.33. Lettuce production was up to 5.65 kg/m2, significantly higher than previous reports, largely because of high nutrients reuse efficiency from the anaerobic supernatant that contained 130 and 34 mg/L N and P, respectively. Of the feed carbon, 24.5% was taken up by fish biomass. Fish solid wastes contained 38.2% carbon, of which 91.9% was recovered as biogas (74.5% CH4). Biogas production was 0.84 m3/kg for fish sludge and 0.67 m3/kg for dry plant material. CO2 sequestration was 1.4 higher than the feed carbon, which reduced the system's carbon footprint by 64%. This study is the first to demonstrate highly efficient fish and plant production with near-zero water and waste discharge and with energy recovery that can potentially supply the system's energy demand.

Crop residues, such as toxic tomato plant wastes, often cause environmental and economic burdens. Anaerobic digestion of these residues, which contain hardly biodegradable lignocellulosic content and low C/N (~10), was not thoroughly studied or practiced. This study investigated the impacts of temperature and particle size on anaerobic degradation performance of tomato plant waste in both laboratory and field scales (the latter was studied for one year under desert conditions). The highest batch degradation rate was observed for the smallest particles

Use of recirculating aquaculture systems (RAS) to grow fish is on the rise. Fish feed typically contains 25–60% protein and is the only significant input in RAS. Fish recover 20–30% of the applied feed as biomass, and the unassimilated nitrogen is released into the water, mainly as ammonia, which is toxic to fish. Nitrification is the most common treatment practice, converting ammonia to the less toxic nitrate, and nitrogen removal is achieved by either water exchange or denitrification. The aim of this study was to develop and test a novel approach to remove nitrogen based on a microaerophilic assimilation side-reactor. In the suggested system, fish solid waste and dissolved nitrogen are assimilated into protein-rich microbial biomass, which has the potential to partially offset fish feed input. Initially, a theoretical model based on the system’s nitrogen mass balance was established. Then, an intensive pilot-scale RAS was constructed, growing ∼50 kg fish/m3. The system consisted of a fish tank, solids filter, and microaerophilic assimilation reactor based on activated sludge treatment. Intrinsic solid waste and wheat-flour waste were used as carbon source. After a trial run of about 2.5 months, the RAS was tested for 101 days. Average total ammonia nitrogen, nitrite, and nitrate removal were 89.1, 69.4 and 100%, respectively. Of the introduced solids, over 82% were lost as carbon dioxide by respiration, 11.7% were recovered as microbial biomass and 6.5% as fish biomass, and only 0.6% remained in the water. Biomass organic content was similar to aquafeed and nitrogen content was equivalent to 40% crude protein. Daily energy demand for the system’s designed capacity of 80 kg/m3 would result in a low energy consumption of 7.72 kW h/kg fish. Overall, a novel concept for sustainable production in intensive aquaculture was developed and successfully demonstrated in a pilot-scale RAS.

Poor sanitation due to improper treatment of human excreta, and energy scarcity are global problems with only partial solutions. Thus, feasible conversion of human excreta into safe, reusable “products” and renewable energy could be advantageous. The research objectives were to study the properties and major chemical processes occurring during hydrothermal carbonization of raw human excreta with typical solids content, as well as exploring potential use of the resulting hydrochar and aqueous phase. Human excreta (often considered as black water) were hydrothermally carbonized in a set of nine 50-mL laboratory batch reactors under a range of severities, a single parameter obtained from a coalification model that represents the combination of temperature and time. Three temperatures (180, 210 and 240 °C) and reaction times (30, 60 and 120 min) were used. The physicochemical characteristics such as yield, elemental composition, organic matter and calorific value of the hydrochar (solid phase) were studied. Aqueous phase was characterized for carbon, nitrogen, macro and micronutrients composition. In addition, the potential use of the hydrochar and aqueous phase were studied. There was high correlation between severity factor and carbon content (R2 = 0.95) and calorific value (R2 = 0.89). Hydrochar yield decreased with increasing severity from 69 to 56%. Calorific values increased from 24.7 to 27.6 MJ/kg, falling within the calorific range of sub-bituminous coal. The aqueous phase demonstrated high nitrogen concentration, reaching up to 8178 mg/L total nitrogen, while N:P:K ratios were similar to those of commercial fertilizers. Pilot scale experiments resembled the results found in laboratory scale experiments for both hydrochar and aqueous phase and fitted the regression curves obtained from the severity factor. It is postulated that hydrothermal carbonization of human excreta could potentially serve as a sustainable sanitation technology with a closed-loop cycle approach while recovering energy and nutrients.

Hydrothermal carbonization (HTC) of raw and anaerobically digested (AD) manure with either water or whey was studied, with the goal of recovering energy and nutrients. Specifically, the impacts of HTC reaction temperature (180–240 °C), solid feedstock, and type of liquid on hydrochar quality and aqueous phase properties were tested. Of the hydrochars produced, the calorific value of whey-based hydrochar was the highest, (19.4 and 16.0 MJ/kg for manure and digestate, respectively). Overall, the net energy gain was higher for HTC of manure with whey (7.4–8.3 MJ/kg dry feedstock) and water (4.4–5.1 MJ/kg) compared to the combined AD-HTC process with whey (4.4–5.3 MJ/kg) and water (2.3–2.9 MJ/kg). Digestate-derived hydrochar contained up to 1.8% P, higher than manure-derived hydrochar (≤1.5%). Using whey as a liquid for HTC increased the aqueous-phase N-P-K concentrations up to 3,200, 410, and 7,900 mg/L, respectively, suggesting its potential use as a liquid fertilizer.

Aquaponics plant waste, such as the non-edible parts of many vegetable crops, can be a source of environmental pollution, while its treatment might cause an economic burden. Therefore, efficient use of this waste would be advantageous. This study aimed at investigating anaerobic digestion of aquqponic lettuce waste to recover nutrients and energy through biogas production. A 700 L commercial anaerobic system was used to treat lettuce wastes from an aquaponic farming system that operated under desert climate and steady-state conditions. Digestion efficiency of the lettuce waste was 90.1% by weight, producing a maximum biogas volume of 0.65 m3/kg dry weight per day. Biogas composition contained on average 59.2% methane and 38.9% CO2 with only negligible hydrogen sulfide content. Moreover, the supernatant from the anaerobic digester contained elevated nutrient concentrations (N, P, K, Ca, and Fe), which can potentially be used onsite as a fertilizer. Onsite anaerobic digestion of lettuce plant waste from the aquaponic system under summer desert conditions is demonstrated for the first time to efficiently reduce pollution burden, produce high-quality biogas, and recover nutrients.

Water-Food-Energy (WFE) resources exert mutual influences upon each other and thus cannot be managed separately. Information on household WFE expenditures addresses knowledge that distinguishes between geospatial districts' social welfare. Social welfare and investment in districts' WFE resources are interconnected. District (node) product of WFE normalized expenditures (Volume) is considered as a representative WFE Nexus holistic quantity. This Volume is assumed to be a function of residents' knowledge of welfare level across districts. We prove that the Volume rate conforms to Boltzmann entropy, and this is the premise of our hypothesis for directed information from high to low welfare between network nodes. Welfare mass (WM) represents the district's Volume combined with its income and population density. This WM is used as input into a model balancing between all domain nodes that allows policymakers to simulate the effects of potential quantifiable policy decisions targeted to individual districts at a domain level while also considering influences between districts. Based on existing historic data, the established tool exemplifies its potential by providing outcomes for Israel districts showing the influence of imposing different temporal allocation/deallocation actions as managerial regulations to prescribed districts. It is found that districts with a high WM do not suffer when a defund is applied, but districts that have a low WM gain from subsidies., Finite Element Methods; Computational Fluid Dynamics; Wave Physics; Mathematical physics; Sustainable Development; Contaminant Transport; Environmental Risk Assessment; Groundwater; Water-Food-Energy (WFE) Nexus; Decision Support Systems (DSS); Integrated Water Resource Management and Policy (IWRMP).

Lately, there has been a growing interest in converting low-cost biomass residuals, including wastewater sludge, into char-like materials for various applications. In this research, ammonium (NH4+) adsorption and desorption potential of hydrochar activated via Fenton oxidation were systematically investigated. Hydrochar was prepared from domestic wastewater treatment plant sludge and activated by Fenton oxidation using different H2O2 concentrations, H2O2/Fe2+ ratios, and activation times. The activated hydrochars (AHs) were characterized by ATR-FTIR, high-resolution XPS, BET specific surface area, and SEM, and their NH4+ adsorption capacity was analyzed. The NH4+ adsorption isotherms and kinetics, adsorption in the presence of competing ions (with and without humic acid), and NH4+ desorption were investigated. The results show that following hydrochar activation, the acidic groups’ concentration and the BET surface area increased, but the morphology remained essentially unchanged. It was also found that the activation occurs within a few minutes when using a relatively low concentration of reagents, and without extensive post-treatment steps. The NH4+ adsorption onto AH at equilibrium fitted the Langmuir isotherm model, with a maximum adsorption capacity of 30.77 mg g−1, and the NH4+ adsorption kinetics fitted the pseudo-second-order model. NH4+ adsorption in the presence of competing ions decreased by up to 33 ± 3%. NH4+ desorption experiments demonstrated that NH4+ recovery can reach 33 ± 5% with ultrapure water and 67 ± 2% with 2 M KCl. The results of this study indicate that Fenton oxidation is a promising alternative for hydrochar activation, and can be used as an adsorbent for NH4+ remediation in wastewater treatment processes.

Wet organic waste, including animal manures, sewage and activated sludge, and the organic portion of municipal solid waste, represents both a burden that must be dealt with as well as a material source for fertilizer and compost. Depending on how these wastes are treated, their properties and behavior when applied to soils can vary significantly. The high water-fraction present in wet organic waste is commonly a disadvantage in various treatment techniques such as composting and pyrolysis, requiring drying or the addition of dry matter. Similarly, a low C:N of some of these sources (e.g. poultry manure and domestic sludge) may be challenging for commonly used biological treatments. Hydrothermal carbonization (HTC) is a technology that, as suggested by its name, involves the presence of large water fractions, thus it is ideally suitable for the treatment of wet organic waste. This chapter will introduce the HTC process, providing an overview of the main chemical conditions and reactions involved in the conversion of wet organic waste. Then, the various applications of the generated products will be discussed, with a particular focus on the addition to soils.

The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 °C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 °C, and decreased with hydrochar generated at 250 °C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.

Phosphorus (P) is an essential element for life that is introduced through feed in modern aquaculture-the fastest growing food production sector. P can also be a source of environmental contamination and eutrophication if mistreated. Fish assimilate only 20-40% of the applied P; the rest is released into the water. The goals of this research were to study the fate of P in a novel intensive near-zero discharge (

There is a recognized need for mineralizing aquaculture-derived sludge in aquaponics systems in order to reduce waste production. Many recent studies of aquacultural waste treatment have focused only the production of biogas as opposed to the potential for mineralization of nutrient-rich sludge. Upflow anaerobic sludge blanket (UASB) reactors provide one possible solution for breaking down sludge into bioavailable nutrients that can subsequently be delivered to plants. As such, this study examines the mineralization performance of sequential UASB reactors that are designed with an expanded granular sludge bed (EGSB) and compared to standard aerobic and anaerobic batch reactors. Results of our experiments demonstrate that only chemical oxygen demand reduction is significantly different. An unexpected drop in pH of one of the three reactor systems revealed that a pH below 6 was able to significantly increase the mineralization and mobilization of nutrients. Approximately 25% of phosphorus, potassium, and calcium could also be recovered from the sludge under lower pH conditions, as compared to the mineralization performance of standard UASB reactors running at a higher pH. However, the opposite effect was observed with respect to organic sludge reduction, where diminished performance was observed in the low-pH reactor. The current study implies that anaerobic reactors operating at low pH can potentially contribute towards improved nutrient recovery in multi-loop aquaponics systems and reduction of additive agents for pH control of the hydroponic subsystem.

Onsite separation of black water from greywater (GW) and the latter's onsite reuse have gained popularity in the last three decades. The potential benefits of GW reuse are wide, ranging from direct benefits for the user to large-scale benefits for the whole water sector. However, along with its benefits, GW reuse may pose some risks and challenges that must be mitigated for safe reuse. The challenges are generally divided into health risks, mainly from the presence of pathogenic microorganisms, and environmental risks from the presence of various pollutants, such as sodium, pH and surfactants. This short review highlights the potential benefits of GW reuse along with its major associated challenges, and suggests means to sustainably ensure safe GW reuse.

Growing amounts of poultry litter call for improved treatment solutions. Its conversion to renewable energy can offer a solution while concomitantly reducing environmental impact and reliance on fossil fuels. We compared the production and combustion of biochar by slow pyrolysis to that of hydrochar by hydrothermal carbonization (HTC) in terms of char behavior, energetics, and gas emissions. Poultry litter is significantly different from other feedstocks when treated by slow pyrolysis and HTC, and requires a detailed study of its combustion behavior before it can be utilized in large-scale energy generation. Poultry litter was converted to biochar at 450 °C, and to hydrochar at 180, 200, 220 and 250 °C. Their chemical composition, combustion behavior and gaseous emissions were characterized by TGA–FTIR analysis. Hydrochar produced at 250 °C was more energy-dense than biochar, resulting in 24% higher net energy generation. Combustion behavior of hydrochar produced at 180, 200 and 220 °C was similar to that of the original litter, which is typical of biomass. On the other hand, hydrochar produced at 250 °C and biochar were more similar to coal. The main gaseous emissions during char production were CO 2 , CH 4 and H 2 S. During the combustion step, NO and SO 2 emissions were higher for hydrochar than biochar. Increasing HTC production temperature decreased emissions of CH 4 and NH 3 during hydrochar combustion. Biochar’s emissions were more significant during the production step than during combustion, whereas the opposite held true for hydrochar. Thus, HTC was seen to convert poultry litter more efficiently into a solid fuel that can potentially replace 10% of coal in the generation of electricity, thereby significantly reducing greenhouse gas emissions associated with electricity generation and agricultural waste.

A near-zero waste treatment system for food processing wastewater was developed and studied. The wastewater was treated using an anaerobic membrane bioreactor (AnMBR), polished using an outdoor photobioreactor for microalgae cultivation (three species were studied), and excess sludge was treated using hydrothermal carbonization. The study was conducted under arid climate conditions for one year (four seasons). The AnMBR reduced the total organic carbon by 97%, which was mostly recovered as methane (~57%) and hydrochar (~4%). Microalgal biomass productivity in the AnMBR effluent ranged from 0.25 to 0.8 g·L−1·day−1. Nitrogen (N) and phosphorous (P) uptake varied seasonally, from 18 to 45 mg·L−1·day−1 and up to 5 mg·L−1·day−1, respectively. N and P mass balance analysis demonstrated that the process was highly efficient in the recovery of nitrogen (~77%), and phosphorus (~91%). The performance of the microalgal culture changed among seasons because of climatic variation, as a result of variation in the wastewater chemistry, and possibly due to differences among the microalgal species. Effluent standards for irrigation use were met throughout the year and were achieved within two days in summer and 4.5 days in winter. Overall, the study demonstrated a near-zero waste discharge system capable of producing high-quality effluent, achieving nutrient and carbon recovery into microalgae biomass, and energy production as biogas and hydrochar.

Expansion of dryland agriculture requires intensive supplement of organic fertilizers to improve the fertility of nutrient-poor desert soils. The environmental impact of organic supplements in hot desert climates is not well understood. We report on seasonal emissions of nitrous oxide (N2O) from sand and loess soils, amended with limed and non-limed anaerobic digestate of poultry manure in the Israeli Negev desert. All amended soils had substantially higher N2O emissions, particularly during winter applications, compared to unammended soils. Winter emissions from amended loess (10–175 mg N2O m− 2 day− 1) were markedly higher than winter emissions from amended sand (2–7 mg N2O m− 2 day− 1). Enumeration of marker genes for nitrification and denitrification suggested that both have contributed to N2O emissions according to prevailing environmental conditions. Lime treatment of digested manure inhibited N2O emissions regardless of season or soil type, thus reducing the environmental impact of amending desert soils with manure digestate.

In response to increasing demand for aquaculture products and strict new regulations on organic matter and nitrogen discharge, inland closed recirculating aquaculture systems (RASs) are being developed as a viable eco-sustainable alternative to traditional aquaculture (e.g. ponds, raceways and cages) because of their minimal environmental impact and controlled operation. Fish feed is virtually the only source of carbon and nitrogen to the system. It is estimated that 20 to 30% of the feed nitrogen and 50% of the feed carbon are assimilated or utilized by the fish, while the rest is released to the water. Understanding the fate and utilization of these elements can help optimize RAS efficiency and economics. The fate of carbon and nitrogen was studied by mass balance in a novel near-zero discharge ( 2 and the rest (5%) remained as nondegradable carbon in the UASB. Using the UASB can save up to 12% of the system's energy demands, both directly as energy (methane) input and indirectly by reducing the system's oxygen demand. Of the feed nitrogen, 29% was assimilated by the fish and bacteria in the nitrification reactor and 40–50% was removed in the denitrification reactor, of which 10–20% was removed by anammox. Lastly, ~ 20% of the nitrogen was removed in the UASB reactor, likely by precipitation. It was demonstrated that the system was operating at high stocking density, with almost complete nitrogen and carbon removal and energy recovery. Statement of relevance The fate of carbon and nitrogen was studied by mass balance in a novel near-zero discharge (

Cryptocaryon irritans, a marine protozoan fish parasite with a life cycle that includes cyst formation, constitutes a major concern in intensive recirculating aquaculture systems (RASs), due to its potential propagation in a system with high fish density and minimal water change. In this study, the survival of C. irritans in sludge collected from an up-flow anaerobic sludge blanket (UASB) reactor of a RAS system was studied using a PCR assay. The detection sensitivity of the different life stages in sludge was determined to be 50 tomonts, 5 theronts and 5 trophonts. Dead C. irritans DNA was not detectable after 24 h of inoculation. The survival of the different C. irritans life stages in anaerobic conditions, as present in the UASB reactor, was evaluated. Theronts died within 3 h post-exposure to anaerobic conditions. Protomonts encysted within a day post-exposure, but unlike in aerobic conditions, the resulting tomonts did not hatch. Excystment of theronts from tomonts was delayed in anaerobic conditions, and occurred only after transfer to an aerobic environment. However, the tomonts did not die after 96 h of such exposure and the release rate of theronts did not decrease, compared to the control. The results suggest that infective theronts cannot originate from the UASB reactor and protomonts or theronts that reach the UASB do not survive. However, tomonts appear to be able to survive the reactor's conditions, and if they are released from it with the water outflow, they could hatch in aerobic parts of the RAS.

Millions of decentralized graywater-reuse systems are operating worldwide. This water is directly accessible to household inhabitants, raising environmental and public health concerns. Graywater may contain a variety of harmful organisms, the types and numbers of which vary with source-type, storage time, and background levels of infection in the community source. In this review, we find that most studies indicate high amounts of microbial pathogens in raw graywater and therefore treatment and disinfection are recommended to lower possible health risks. Where these recommendations have been followed, epidemiological and quantitative microbial risk-assessment studies have found negligible health risks of bacterial pathogens in treated graywater. Chlorine is currently suggested as the most cost-effective disinfection agent for inactivating graywater bacterial pathogens and preventing regrowth. Various studies demonstrate that the introduction and diversity of pathogenic bacteria in the soil via irrigation can be affected by several factors, but treated graywater may not be a major contributor of bacterial contamination or antibiotic resistance. However, an accurate assessment of the infectious capabilities, exposure pathways, and resistance of specific pathogens, particularly viruses and antibiotic-resistant bacteria found in treated graywater after disinfection, as well as in the graywater piping, irrigated soils, plants, and associated aerosols is largely lacking in the literature. In addition, research shows that fecal bacterial indicators might not reliably indicate the presence or quantities of pathogens in graywater and thus, the indicator standard for graywater contamination should be revised.

Aquaculture contributes to global food security, producing over 70 million tons of fish and aquatic products annually. Protein rich fish feeds, together with labor costs are the most expensive component costs in aquaculture. Feed application is given as percent of fish weight and therefore, reliable biomass assessment is essential for profitable and environmentally sound aquaculture. Fish biomass estimates are typically based on sampling2% of the fish population. The goals of this research were to estimate potential biases associated with fish sampling in recirculating aquaculture systems (RAS), and the potential economic and environmental implications of such biased estimations. The size of the biased sampling-based estimates of fish biomass in two cultured species was shown to be larger than what the confidence interval suggests, even after20% of the population was sampled. Such biases, if indeed common, will most likely result in over/underfeeding, both entailing negative economic and environmental consequences. We advocate conducting similar studies with major cultured fish to generate "bias correction tables" for adjusting fish feeding rate to bias-corrected biomass. These will help reduce the potential economic losses and negative environmental impacts of aquaculture practice.

Glutamate Dehydrogenase 1 (GDH), encoded by the Glud1 gene in rodents, is a mitochondrial enzyme critical for maintaining glutamate homeostasis at the tripartite synapse. Our previous studies indicate that the hippocampus may be particularly vulnerable to GDH deficiency in central nervous system (CNS). Here, we first asked whether mice with a homozygous deletion of Glud1 in CNS (CNS-Glud1 -/- mice) express different levels of glutamate in hippocampus, and found elevated glutamate as well as glutamine in dorsal and ventral hippocampus, and increased glutamine in medial prefrontal cortex (mPFC). l-serine and d-serine, which contribute to glutamate homeostasis and NMDA receptor function, are increased in ventral but not dorsal hippocampus, and in mPFC. Protein expression levels of the GABA synthesis enzyme glutamate decarboxylase (GAD) GAD67 were decreased in the ventral hippocampus as well. Behavioral analysis revealed deficits in visual, spatial and social novelty recognition abilities, which require intact hippocampal-prefrontal cortex circuitry. Finally, hippocampus-dependent contextual fear retrieval was deficient in CNS-Glud1 -/- mice, and c-Fos expression (indicative of neuronal activation) in the CA1 pyramidal layer was reduced immediately following this task. These data point to hippocampal subregion-dependent disruption in glutamate homeostasis and excitatory/inhibitory balance, and to behavioral deficits that support a decline in hippocampal-prefrontal cortex connectivity. Together with our previous data, these findings also point to different patterns of basal and activity-induced hippocampal abnormalities in these mice. In sum, GDH contributes to healthy hippocampal and PFC function; disturbed GDH function is relevant to several psychiatric and neurological disorders.

This study investigated the feasibility of using hydrothermal carbonization (HTC) aqueous phase as an alternative nutrient source for microalgae cultivation, and the microalgae cultivation capability to treat this complex medium to a level enabling its reuse or discharge. HTC of activated sludge was optimized in terms of the energy content of the solid hydrochar and the nutrient content of the HTC aqueous phase adequate for microalgal growth. Growth rates of Coelastrella sp. and Chlorella sp. in the HTC aqueous phase based growth medium and a control medium (mBG11) were similar, indicating that the HTC aqueous phase does not inhibit the microalgae growth. Nitrogen and phosphorus concentrations were reduced by >90% and dissolved organic carbon by 80% after 6 days of cultivation, resulting in water quality suitable for reuse or discharge. This study confirms the microalgae high potential in a circular bio-economy to valorize wet bio-waste streams from various treatment methods.

Recirculating aquaculture systems, as part of aquaponic units, are effective in producing aquatic animals with a minimal water consumption through effective treatment stages. Nevertheless, the concentrated sludge produced after the solid filtration stage, comprising organic matter and valuable nutrients, is most often discarded. One of the latest developments in aquaponic technology aims to reduce this potential negative environmental impact and to increase the nutrient recycling by treating the sludge on-site. For this purpose, microbial aerobic and anaerobic treatments, dealt with either individually or in a combined approach, provide very promising opportunities to simultaneously reduce the organic waste as well as to recover valuable nutrients such as phosphorus. Anaerobic sludge treatments additionally offer the possibility of energy production since a by-product of this process is biogas, i.e. mainly methane. By applying these additional treatment steps in aquaponic units, the water and nutrient recycling efficiency is improved and the dependency on external fertiliser can be reduced, thereby enhancing the sustainability of the system in terms of resource utilisation. Overall, this can pave the way for the economic improvement of aquaponic systems because costs for waste disposal and fertiliser acquisition are decreased.

In abattoir operation, paunch waste can present a major problem when flushed with water and discharged. Collected and processed separately, it provides a means of reusing organic carbon and nutrients. Hydrothermal carbonisation (HTC) is a means to process the waste that overcomes some problems of composting and anaerobic digestion. Experiments were conducted to investigate HTC of cattle paunch waste to hydrochar under different conditions. The fuel characteristics of hydrochar were tested for the potential in electricity generation and the nutrient concentrations of liquid were analysed for soil fertilization. The carbon content of paunch increased (∼15%) after HTC. It was also reflected in its increasing calorific value. The changes in the H/C and O/C ratios, analysed using the van Krevelen diagram, showed that the fuel properties of hydrochar improved noticeably after carbonisation. The TOC and TN concentrations in the liquid changed significantly with increasing temperature and time. With increasing moisture, the nutrient concentrations decreased, because of dilution effect. The liquid product contained significant levels of N, C and K; but may need suitable dilution before applying as a fertiliser. An energy balance showed that a fraction (

Greywater (GW) reuse can alleviate water stress by lowering freshwater consumption. However, GW contains pathogens that may compromise public health. During the GW-treatment process, bioaerosols can be produced and may be hazardous to human health if inhaled, ingested, or come in contact with skin. Using air-particle monitoring, BioSampler®, and settle plates we sampled bioaerosols emitted from recirculating vertical flow constructed wetlands (RVFCW) - a domestic GW-treatment system. An array of pathogens and indicators were monitored using settle plates and by culturing the BioSampler® liquid. Further enumeration of viable pathogens in the BioSampler® liquid utilized a newer method combining the benefits of enrichment with molecular detection (MPN-qPCR). Additionally, quantitative microbial risk assessment (QMRA) was applied to assess risks of infection from a representative skin pathogen, Staphylococcus aureus. According to the settle-plate technique, low amounts (0-9.7×10(4)CFUm(-2)h(-1)) of heterotrophic bacteria, Staphylococcus spp., Pseudomonas spp., Klebsiella pneumoniae, Enterococcus spp., and Escherichia coli were found to aerosolize up to 1m away from the GW systems. At the 5m distance amounts of these bacteria were not statistically different (p>0.05) from background concentrations tested over 50m away from the systems. Using the BioSampler®, no bacteria were detected before enrichment of the GW-aerosols. However, after enrichment, using an MPN-qPCR technique, viable indicators and pathogens were occasionally detected. Consequently, the QMRA results were below the critical disability-adjusted life year (DALY) safety limits, a measure of overall disease burden, for S. aureus under the tested exposure scenarios. Our study suggests that health risks from aerosolizing pathogens near RVFCW GW-treatment systems are likely low. This study also emphasizes the growing need for standardization of bioaerosol-evaluation techniques to provide more accurate quantification of small amounts of viable, aerosolized bacterial pathogens.

Environmentally responsible disposal of solid organic wastes from land-based brackish and marine recirculating aquaculture systems is critical for promoting widespread acceptance and implementation, but conversion efficiency of saline sludge to biomethane is generally low. We describe the development of a microbial consortium that can convert marine organic fish waste solids to biomethane at over 90% efficiency. The halotolerant microbial consortium, which was developed by sequential transfer in seawater with fish waste, is optimized for low COD:N ratios typical of organic fish waste and does not require addition of amendments such as organic carbon or nutrients. Temperatures for maximum rates of conversion range from 26 to 35 °C. Five predominant phylotypes identified in the microbial consortium by denaturing HPLC were isolated. Two isolates included anaerobic fermentative bacteria identified as a strain of Dethiosulfovibrio and a strain closely related to Fusobacterium spp., which both hydrolyze and ferment proteins, peptides and amino acids. The other three isolates included an acetate-utilizing methanogenic archaeon identified as a strain of Methanosarcina and two hydrogen-utilizing methanogenic archaea identified as strains of Methanogenium and Methanoplanus . Bioconversion rates of sterile fish waste with the reconstituted microbial consortium containing all five isolates were equivalent to rates observed with the original enriched consortium after one sequential transfer. The results demonstrate unequivocally that halotolerant consortia of bacteria and archaea can be developed for bioconversion of saline organic solid waste with high efficiencies equivalent to those attained with non-saline waste systems. Understanding the microbial community composition is critical for management of solid organic waste from land-based marine aquaculture systems and to maintain or restore microbiota during start up and throughout the production process. Statement of relevance Appropriate disposal of solid organic wastes from land-based brackish and marine recirculating aquaculture systems is critical for promoting widespread acceptance and implementation. We demonstrate that halotolerant consortia of bacteria and archaea can be developed for bioconversion of saline fish waste with high efficiencies equivalent to those attained with non-saline waste systems.

Disease outbreaks are a major concern in aquaculture. This is particularly true in intensive recirculating aquaculture systems (RASs), due to the high rearing densities in a system where high concentrations of organic matter are produced with minimal water exchange. This study assessed the survivability of the common fish pathogen Streptococcus iniae in a solid-removal unit of a RAS, the upflow anaerobic sludge blanket (UASB). A PCR detection method, along with an improved protocol for the extraction of high-quality DNA from sludge samples, were utilized for this purpose. This method enabled detection of S. iniae at a minimum concentration of 7.6 × 10 5 CFU mL − 1 raw sludge. We examined the survivability of S. iniae in batch digesters, which consisted of sealed serum bottles filled with sludge from the UASB reactor, and in laboratory-scale flow-through UASB reactors that were continuously fed with fish waste sludge. Results demonstrated a gradual decrease in the intensity of the PCR-amplified product to the point of no detection in either batch or UASB digesters, suggesting that the conditions present in the UASB reactor are not favorable for S. iniae . The PCR-based detection method was successfully applied to sludge from a commercial RAS enabling detection of potentially pathogenic bacteria. Statement of relevance The manuscript addresses the control of bacterial disease-causing agent in a near-zero discharge aquaculture system which contains a novel solid removal unit. The bacteria studied is S. iniae , a significant disease-causing agent in aquaculture. The potential threat of disease outbreaks increases with the intensification of the culture system, such as the one described and analyzed in this study. This intensification is of high relevance to the industry, as it reduces environmental contamination due to fish production as well as enables fish culture in places distant from a natural water source.

On-site in-vessel composting of sewage sludge is considered to be applied in Israel for peripheral wastewater treatment plants (WWTPs). Based on lab-scale simulations using municipal sewage sludge and green waste, this study identifies a prospective range of values related to biomass stabilization during short-term processing. Within two weeks, 26–30% of the initial organic carbon was released as CO2, potential heat formation was decreased by 73–82%, and odor emissions by 87–99.5%. This reduction was mainly associated with co-decrease of NH3, dimethyl disulfide, and dimethyl trisulfide. Phytotoxicity was reduced by 28–52% whereas some residual toxicity might be attributed to non-biodegradable inorganic compounds. Stabilization rates observed in flexibly controlled lab-scale simulations can represent closed and efficiently aerated large-scale industrial systems. These prospective ranges of stabilization parameters are critical for deciding on the necessity of a curing stage for on-site enclosed installations in WWTPs.

This study represents the first systematic attempt to evaluate antibiotic-resistant bacteria (ARB) occurrence in treated greywater and the potential spread of these bacteria from the greywater to greywater-irrigated soil. Treated greywater from three recirculating vertical flow constructed wetlands, each located in a household in the central Negev Desert, Israel, was surveyed. The presence of antibiotic-resistant bacteria in raw and treated greywater was investigated with culture and molecular methods, as well as their presence in the corresponding treated-greywater-irrigated soils. Additionally, the effectiveness of chlorination to prevent the spread of ARB was tested. The total count of tetracycline-resistant bacteria significantly increased in the treated greywater, likely due to their concentration on the filter matrix of the treatment systems. Twenty-four strains of tetracycline-resistant bacteria were isolated and identified at the genus level by 16Sr RNA gene sequencing. All the tetracycline-resistant bacteria showed high resistance traits, and some of them presented multiple antibiotic resistances. Six tetracycline resistance genes (coding for efflux and ribosomal resistance mechanisms) and five β-lactamase genes were detected. In 14 of the isolated strains, the gene tet39, which is phylogenetically related to both environmental and clinical strains, was identified. All the tet39 resistant bacteria were positive to at least one of the β-lactamase genes tested. Chlorination was found to be an efficient method to reduce ARB in treated greywater. We concluded that disinfection of treated greywater may reduce the risks not only from the potential presence of pathogens but also from the presence of ARB and antibiotic resistance genes.

Biodegradation is a fundamental process for removal of the environmentally prevalent herbicide, atrazine, from contaminated waters. Biodegradation is more efficient when bacteria are attached on surface of an adsorbing carrier that supports the microbial population. However, for various reasons, biodegradation is almost always monitored in the liquid phase. In this study, we employ a novel Quartz Crystal Microbalance with Dissipation technique (QCM-D) for continuous, real-time monitoring of the attachment of atrazine-degrading bacteria to the surface, atrazine adsorption and degradation, and the consequent proliferation of the irreversibly attached sessile bacteria. The effect of atrazine biodegradation was observed in a batch mode of operation, in which a significant frequency decrease of the piezoelectric sensor was observed in the QCM-D, due to the proliferation of atrazine-degrading bacteria on the expense of atrazine. The latter was confirmed microscopically. Results also suggest that the viscoelastic properties of the atrazine-degrading consortium immediately changed in response to the presence of atrazine, whereas those of the non-degrading consortium were not affected. Importantly though, atrazine adsorption was similar regardless of the sessile consortia layers. When the QCM-D flow cell was exposed to a continuous flow of saturated atrazine solution, the degrading consortium layer was significantly more fluidic compared to batch mode conditions. The magnitude and kinetics of atrazine adsorption, which were monitored using QCM-D, were higher on bacterial cells comparing to the pristine, polystyrene-coated sensor. Findings from the current study can improve bioremediation design and open an avenue for studies on biodegradation and adsorption of micro-pollutants using QCM-D technology.

The development of intensive recirculating aquaculture systems (RAS) with low water exchange has accelerated in recent years as a result of environmental, economic and other concerns. In these systems, fish are commonly grown at high density, 50 to 150 kg/m3, using high-protein (30%–60%) feeds. Typically, the RAS consists of a solid treatment and a nitrification unit; in more advanced RAS, there is an additional denitrification step. Nitrous oxide (N2O), a byproduct during nitrification and denitrification processes, is a potent greenhouse gas that destroys the ozone layer. The aim of this study was to measure and assess N2O emissions from a near-zero discharge land-based saline RAS. N2O flux was monitored from the RAS's fish tank, and moving-bed nitrification and activated-sludge (with intrinsic C source) denitrification reactors. N2O emission potential was also analyzed in the laboratory. N2O flux from the denitrification reactors ranged between 6.5 and 48 mg/day, equivalent to 1.27 ± 1.01% of the removed nitrate-N. Direct analysis from the fish tank and nitrification reactors could not be performed due to high aeration, which diluted the N2O concentration to below detection limits. Thus, its potential emission was estimated in the laboratory: from the fishponds, it was negligible; from the nitrification reactor, it ranged between 0.4 and 2.8% of the total ammonia-N oxidized. The potential N2O emission from the denitrification reactor was 3.72 ± 2.75% of the reduced nitrate-N, within the range found in the direct measurement. Overall, N2O emission during N transformation in a RAS was evaluated to be 885 mg/kg feed or 1.36 g/kg fish production, accounting for 1.23% of total N application. Consequently, it is estimated that N2O emission from aquaculture currently accounts for 2.4% of the total agricultural N2O emission, but will decrease to 1.7% by 2030.

Anaerobic digestion (AD) of sulfate-rich brackish aquaculture sludge (BAS) is an effective method to reduce negative environmental impact and produce biogas. However, the mechanisms of electron-acceptor utilization during AD of BAS, and the effects of elevated sulfate, nitrate and nitrite levels on biogas production, have never been investigated. The current study is the first to demonstrate the mechanisms of electron-acceptor utilization in BAS under methanogenic conditions. Nitrate, nitrite and iron were almost completely depleted during the first day of AD, and methane production began only when these electron acceptors were removed. In contrast, sulfate reduction also started immediately, but took 15–28 d, dependent on the treatment, and largely coincided with methane production. The volume of produced biogas, the lag phase for methane production and methane content in the biogas were affected by the inhibition of sulfate reduction and by the increase in nitrate and nitrite concentrations. However, the average methane-production rates in all treatments were similar. Our data suggest that methanogenesis in BAS under naturally high sulfate levels results in the highest possible methane-producing capability of the system; no additional manipulations are required to further increase methane production, suggesting the robustness of AD of BAS under the currently reported conditions.

Natural bodies of open water in desert landscapes are important resources for survival of desert-dwelling animals and in recent years artificial bodies of water may have become equally important. In the present study we are testing if species richness and activity of bats are related to the water chemistry both in natural and artificial bodies of water, and if these measures can indicate water quality in desert habitats where water is scarce. We combined acoustic monitoring of bat activity and species richness in artificial and natural bodies of water in the Negev desert, Israel and measured 27 variables of water chemistry and quality at each site. Significant differences in water chemistry and quality were found between natural and artificial bodies of water. Species richness and activity of bats did not differ between artificial and natural bodies of water, indicating that desert-dwelling bats may benefit from artificial bodies of water, however activity within species differed between natural and artificial bodies of water. Some species of bats were only recorded at natural bodies of water, suggesting that these species are not tolerant to lower quality of water and emphasizes the importance of natural bodies of water in desert ecosystems. Our results demonstrate that community measures, such as total bat activity and species richness of bats in desert habitats, may not be sufficient to indicate changes in water chemistry and quality. Rather it is recommended and applicable to use the activity of specific species as indicators of water quality in desert habitats.

Understanding and optimization of composting processes can benefit from the use of controlled simulators of various scales. The Agricultural Research Organization Composting Simulator (ARO-CS) was recently built and it is flexibly automated by means of a programmable logic controller (PLC). Temperature, carbon dioxide, oxygen and airflow are monitored and controlled in seven 9-l reactors that are mounted into separate 80-l water baths. The PLC program includes three basic heating modes (pre-determined temperature profile, temperature-feedback (“self-heating”), and carbon dioxide-dependent temperature), three basic aeration modes (airflow dependence on temperature, carbon dioxide, or oxygen) and enables all possible combinations among them. This unique high flexibility provides a robust and valuable research tool to explore a wide range of research questions related to the science and engineering of composting. In this article the logic and flexibility of the control system is presented and demonstrated and its potential applications are discussed.

Whole exome sequencing is a diagnostic approach for the identification of molecular etiology in patients with suspected monogenic diseases. In this article we report on our experience with whole-exome sequencing (WES) of DNA samples taken from patients referred for genetic evaluation due to suspected undiagnosed genetic conditions.Exome enrichment was achieved by Nextera Rapid Capture Expanded Exome Kit. Whole-exome sequencing was performed on Illumina HiSeq 2500. Potentially damaging rare variants were selected for familial cosegregation analysis.A total of 39 patients presenting a wide range of phenotypes suspected to have a genetic cause were sent to WES. Approximately 80% were children with neurological phenotypes. Variations having a high probability of being causative were identified in 20 families, achieving a 51.3% molecular diagnostic rate. Among these, 7 exhibited autosomal dominant disease, 12 autosomal recessive diseases and one X-linked disease; 28% of the patients (11/39) were found to carry a novel mutation located in previously reported genes. Novel mutations located in genes not known to be associated with genetic disease were identified in 23% of the patients (9/39).Whole exome sequencing identified the underlying genetic cause in more than half of the patients referred for evaluation in the genetics clinic at the tertiary hospital. These data demonstrate the utility of WES as a powerful tool for effective diagnostics of monogenic genetic diseases.