4,723 research outputs found

    Sewage sludge minimisation by OSA-MBR: A pilot plant experiment

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    This study presents the excess sludge minimisation in a Membrane Bioreactor (MBR) system by an Oxic Settling Anaerobic (OSA) process. The pilot plant was fed with real wastewater and OSA was operated with two different hydraulic retention times (HRT), respectively 4 (Period II) and 6 h (Period III) and compared to an MBR (Period I). Multiple parameters/variables were monitored: sludge minimisation, nitrogen and carbon removal, membrane fouling, and biokinetic behaviour through respirometry. With respect to the current literature, greenhouse gas emissions were also here monitored, often neglected. Results demonstrated that combining MBR and OSA systems can significantly reduce excess sludge production (89.7%, in Period III and 59.7% in Period II, compared to Period I). However, Period III presented better PO4-P removal efficiencies but worse performances in the other parameters (COD, NH4 and Total Nitrogen). No substantial variation in membrane fouling was obtained over the experimental periods. Finally, the HRT increase in the anaerobic reactor promoted a N2O-N increase inside the unaerated reactors, highlighting the need for a trade-off between sludge minimisation and GHG emission

    Amoniak-nitrogen (NH3-N) pada sistem kokultur hewan akuatik dan tanaman padi di air payau

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    Amonia (NH3-N) adalah nitrogen terlarut yang paling berbahaya dari limbah akuakultur. Sebuah eksperimen telah dilakukan untuk mengevaluasi sistem kokultur yang efisien dalam mereduksi NH3-N. Sebanyak 4 spesies hewan akuaktik, yaitu ikan nila (Oreochromis niloticus), udang windu (Penaeus monodon), kerang darah (Tegillarca granosa), dan teripang pasir (Holothuria scabra), serta tanaman padi (Oryza sativa) dikombinasikan pada beberapa sistem akuakultur. Enam perlakuan dan masing-masing dengan tiga ulangan dirancang menggunakan rancangan acak lengkap (RAL). Benih hewan akuatik diaklimatisasi secara bertahap selama 30 hari. Benih padi disemai di air payau, selanjutnya ditebar menggunakan metode apung. Selama 28 hari eksperimen, ikan nila dan udang windu diberi pakan 4 kali sehari dengan feeding rate sebesar 10% bobot biomas, sedangkan kerang darah dan teripang pasar tidak diberikan pakan. Hasil menunjukkan bahwa efisiensi reduksi nutrien (ERN) NH3-N di dua sistem monokultur bernilai negatif, sementara empat sistem kokultur bernilai positif. Nilai ERN dua perlakuan sistem polikultur tidak berbeda (P>0,05). Sementara itu, nilai ERN pada sistem IMTA lebih tinggi dari sistem monokultur maupun polikultur (P<0,05). Temuan ini mengarah pada pemanfaatan keanekaragaman spesies untuk akuakultur berkelanjutan di air payau. Hal ini dapat disimpulkan bahwa sistem akuakultur yang paling efisien dalam mereduksi NH3-N adalah sistem IMTA-padi dengan nilai ERN sebesar 43,3±1,7%. Nilai ini lebih tinggi (P<0,05) dari semua sistem akuakultur lainny

    From Photosynthesis to Detoxification: Microbial Metabolisms Shape Earth’s Surface Chemistry

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    Earth’s chemistry, through geologic time and in the present, is inextricably linked with biologically mediated reactions. All major elemental cycles on Earth’s surface have arisen from two competing processes – life shaping its chemical environment through the evolution of key biochemical pathways, and the environment constraining metabolism by dictating which reactions will occur. Understanding this complicated interplay motivates the research presented in this thesis, which studies this phenomenon over two major elemental cycles – the modern Nitrogen (N) and ancient Carbon (C) cycle. Chapters One and Two focus on the evolution of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), the enzyme that catalyzes the key carbon fixation step in modern oxygenic photosynthesis. This reaction also imparts a large kinetic isotope effect (KIE) that causes the fixed carbon to be relatively depleted in natural abundance ¹³C compared to its substrate; this isotopic fingerprint can be seen in both the modern C cycle and in rock records recording the ancient C cycle. Therefore, this KIE has been used both in vitro (outside the cell) by biochemical models to rationalize rubisco’s reaction mechanism, and in vivo (in the cell) as a proxy for environmental CO₂ concentrations in the past and present. However, both the in vitro and in vivo measurements are calibrated using modern organisms even though rubisco and oxygenic photosynthesis have undergone profound evolution over geologic time. Therefore, we measured the KIE in vitro and in vivo of a reconstructed ancestral Form IB rubisco dating to &gt;&gt; 1 Ga, and the KIE in vitro of a recently discovered Form I’ rubisco that presents a modern analogue to ancestral Form I rubiscos prior to the evolution of the small subunit. Overall, we find that the KIEs of both rubiscos are smaller than their modern counterparts, which is surprising given that the rock record indicates overall carbon isotope fractionations in vivo are larger in the past. In addition, we find that models strictly based on modern organisms may not apply to the past, questioning the basic assumption that uniformitarianism can be readily applied to biological processes. However, these models can be rescued by accounting for other aspects of cell physiology. Chapter Three focuses on disentangling the source of key metabolites, like nitrous oxide (N₂O) in the modern N cycle. Like Chapters 1 and 2, an isotopic fingerprint that measures the ‘preference’ of ¹⁵N for the central or outer nitrogen site in N₂O (“Site Preference” or “SP”) has primarily been calibrated using dissimilatory, or energy-generating, nitric oxide (NO) reductases (NORs). However, there exists a much larger and phylogenetically widespread class of NO-detoxifying enzymes; in particular, flavohemoglobin proteins (Fhp/Hmp) produce N₂O as a strategy to neutralize damaging NO-radicals in anoxic conditions. This enzyme, which generates N₂O in non-growing and anoxic conditions, may be more relevant to natural environments where N₂O production has been detected. Surprisingly, we found that Fhp imparts a distinct SP on N₂O that differs from both bacterial and eukaryotic NORs, and that this value better aligns with existing in situ measurements of N₂O from soils. In addition, we find that in strains with both Fhp and NOR, the Fhp signal dominates when cells are first exposed to high concentrations of NO in oxic conditions while growing before being shifted to an anoxic, non-growing state. Therefore, in addition to telling us ‘Who’s there,’ the SP fingerprint may also be able to tell us something about cell physiology in vivo. We propose a new framework for interpreting the source of N₂O based on SP values.</p

    The method of complex biological water treatment in aquaponic recirculation systems

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    The article discusses the results of experimental research work on the development of technical solutions aimed at creating an integrated innovative biotechnology for recycled water treatment in recirculating aquaculture systems. Schemes and descriptions of experimental units using the multitrophic approach when creating water treatment systems are given. The system is completed according to the principle of integration into a single multitrophic system of spatially delimited biomodules with various types of hydrobionts, where particular types of organisms serve as a food base for subsequent trophic levels. As a result of trophic chains, phytoplankton and zooplankton are cultivated and used as starter live food when rearing juvenile fish. Natural food base contributes to the production of high-quality viable fish stock, which is essential for commercial fish farming. The use of tiered units can significantly reduce the need for production space. Polyculture cultivation of various species of fish, crustaceans, and mollusks together with hydroponic plants allows to diversify production for obtaining additional profit and reducing the risks. Cultivation of high-value fish species (e.g. sturgeon) or crustaceans (Australian red claw) together with less valuable cyprinids, tilapia or African catfish allows to promote products in different market segments

    Increased nitrous oxide emissions from global lakes and reservoirs since the pre-industrial era

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    Lentic systems (lakes and reservoirs) are emission hotpots of nitrous oxide (N2O), a potent greenhouse gas; however, this has not been well quantified yet. Here we examine how multiple environmental forcings have affected N2O emissions from global lentic systems since the pre-industrial period. Our results show that global lentic systems emitted 64.6 ± 12.1 Gg N2O-N yr−1 in the 2010s, increased by 126% since the 1850s. The significance of small lentic systems on mitigating N2O emissions is highlighted due to their substantial emission rates and response to terrestrial environmental changes. Incorporated with riverine emissions, this study indicates that N2O emissions from global inland waters in the 2010s was 319.6 ± 58.2 Gg N yr−1. This suggests a global emission factor of 0.051% for inland water N2O emissions relative to agricultural nitrogen applications and provides the country-level emission factors (ranging from 0 to 0.341%) for improving the methodology for national greenhouse gas emission inventories

    Influence of carbon-coated zero-valent iron-based nanoparticle concentration on continuous photosynthetic biogas upgrading

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    Producción CientíficaThis study assessed the influence of carbon-coated zero-valent nanoparticle concentration (70, 140 and 280 mg L−1) on the performance of photosynthetic biogas upgrading in an indoor pilot scale plant composed of an algal-bacterial photobioreactor interconnected to an external biogas absorption column. In addition, the influence of nanoparticle concentration on the abiotic CO2 gas-liquid mass transfer in the biogas absorption column was also evaluated. Microalgae productivity was enhanced by > 100 % when nanoparticles were added to the cultivation broth, which also boosted nitrogen and phosphorus assimilation from centrate. The biomethane produced complied with most international standards only when nanoparticles were supplemented, achieving CO2 concentrations 98 %) and CH4 concentrations > 94 % in the treated biogas. Finally, this research consistently demonstrated that the improvement of biogas upgrading performance by the addition of nanoparticles was based on a photosynthesis enhancement or stimulation (which significantly increased the pH in the algal cultivation broth) rather than on an improved nanoparticle-mediated CO2 capture in the biogas absorption column.Junta de Castilla y León - EU-FEDER (CLU 2017-09, CL-EI-2021-07 y UIC 315

    Optimisation of small-scale aquaponics systems using artificial intelligence and the IoT: Current status, challenges, and opportunities

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    Environment changes, water scarcity, soil depletion, and urbanisation are making it harder to produce food using traditional methods in various regions and countries. Aquaponics is emerging as a sustainable food production system that produces fish and plants in a closed-loop system. Aquaponics is not dependent on soil or external environmental factors. It uses fish waste to fertilise plants and can save up to 90–95% water. Aquaponics is an innovative system for growing food and is expected to be very promising, but it has its challenges. It is a complex ecosystem that requires multidisciplinary knowledge, proper monitoring of all crucial parameters, and high maintenance and initial investment costs to build the system. Artificial intelligence (AI) and the Internet of Things (IoT) are key technologies that can overcome these challenges. Numerous recent studies focus on the use of AI and the IoT to automate the process, improve efficiency and reliability, provide better management, and reduce operating costs. However, these studies often focus on limited aspects of the system, each considering different domains and parameters of the aquaponics system. This paper aims to consolidate the existing work, identify the state-of-the-art use of the IoT and AI, explore the key parameters affecting growth, analyse the sensing and communication technologies employed, highlight the research gaps in this field, and suggest future research directions. Based on the reviewed research, energy efficiency and economic viability were found to be a major bottleneck of current systems. Moreover, inconsistencies in sensor selection, lack of publicly available data, and the reproducibility of existing work were common issues among the studies

    Novel sinks for the atmospherically potent gas nitrous oxide

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    Nitrous oxide (N2O) is a potent climate gas, with its strong warming potential and ozone-depleting properties both focusing research on N2O sources. While undersaturation in N2O have been reported in natural waters indicating sinks for N2O, most of these found in the surface ocean and shallow freshwaters remain unaccounted for. Although a sink for N2O through biological fixation has been observed in the Pacific, the regulation of N2O- compared to canonical N2 -fixation is unknown. Here I show that both N2O and N2 can be fixed by freshwater communities but with distinct seasonalities and temperature dependencies. N2O fixation appears less sensitive to temperature than N2 fixation, driving a strong sink for N2O in winter. Moreover, by quantifying both N2O and N2 fixation I show that, rather than N2O being first reduced to N2 through denitrification, N2O fixation is direct and could explain the widely reported N2O sinks in natural waters. N2O can be fixed into NH4 + , which could then be further oxidised to NO2 - and NO3 - and being available to the wider community. In the cold, total N2O reduction was higher and a higher proportion of the reduced N2O was conserved. In addition, with activity of nitrification not detected in most of the ponds and anammox not detected in any pond, denitrification seem to be the primary process producing both N2O and N2 . The availability of nitrate limits the temperature sensitivity of the production of N2O and N2 from denitrification, with production of both gases only sensitive to changes in temperature at high concentration of additional nitrate. With the high substrate, the net production ratio of N2O to N2 from denitrification increases at lower temperatures, which could provide more N2O relative to N2 for N fixation in the cold

    Ecology of methanotrophs in a landfill methane biofilter

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    Decomposing landfill waste is a significant anthropogenic source of the potent climate-active gas methane (CH₄). To mitigate fugitive methane emissions Norfolk County Council are trialling a landfill biofilter, designed to harness the methane oxidizing potential of methanotrophic bacteria. These methanotrophs can convert CH₄ to CO₂ or biomass and act as CH₄ sinks. The most active CH₄ oxidising regions of the Strumpshaw biofilter were identified from in-situ temperature, CH₄, O₂ and CO₂ profiles. While soil CH₄ oxidation potential was estimated and used to confirm methanotroph activity and determine optimal soil moisture conditions for CH₄ oxidation. It was observed that most CH₄ oxidation occurs in the top 60cm of the biofilter (up to 50% of CH4 input) at temperatures around 50ºC, optimal soil moisture was 10-27.5%. A decrease in in-situ temperature following CH₄ supply interruption suggested the high biofilter temperatures were driven by CH₄ oxidation. The biofilter soil bacterial community was profiled by 16S rRNA gene analysis, with methanotrophs accounting for ~5-10% of bacteria. Active methanotrophs at a range of different incubation temperatures were identified by ¹³CH₄ DNA stable-isotope probing coupled with 16S rRNA gene amplicon and metagenome analysis. These methods identified Methylocella, Methylobacter, Methylocystis and Crenothrix as potential CH₄ oxidisers at the lower temperatures (30ºC/37ºC) observed following system start-up or gas-feed interruption. At higher temperatures typical of established biofilter operation (45ºC/50ºC), Methylocaldum and an unassigned Methylococcaceae species were the dominant active methanotrophs. Finally, novel methanotrophs Methylococcus capsulatus (Norfolk) and Methylocaldum szegediense (Norfolk) were isolated from biofilter soil enrichments. Methylocaldum szegediense (Norfolk) may be very closely related to or the same species as one of the most abundant active methanotrophs in a metagenome from a 50ºC biofilter soil incubation, based on genome-to-MAG similarity. This isolate was capable of growth over a broad temperature range (37-62ºC) including the higher (in-situ) biofilter temperatures (>50ºC)

    Reuse of Water and Nutrients in Soilless Plant Culture

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    This dissertation proposes two approaches to mitigating the dependency of soilless culture on scarce mineral fertilisers. The first approach aims to increase the lifetime of the NS used in recirculating hydroponic systems, while the second approach presents a holistic method for the treatment and use of aquacultural sludge as NS for soilless growth systems. This method includes two steps: nutrient mobilisation using aerobic digestion (AD), followed by solids precipitation using the biopolymer chitosan as the flocculant. The recovered NS was used to grow lettuce in a recirculating hydroponic system. The outcome of the first approach showed that NS can be used for several weeks before discharge, even though many growers discard recycling NS at weekly intervals. In this study, NS was reused for 6 weeks, corresponding to a production of 1 kg lettuce per 10 litres tank volume of NS, in a closed hydroponic system without compromising the yield and apparent quality of lettuce. The results from the second approach indicated that AD is an efficient method to mobilise nutrients in aquacultural waste to concentrations close to or exceeding the mineral levels recommended for soilless growth systems. In addition, the biopolymer chitosan proved to be an efficient and safe alternative for solids removal from aerobically digested aquacultural waste. The recovered NS was successfully used for lettuce production in a closed hydroponic system, with yield and quality comparable to those of lettuce grown with conventional NS. The results obtained clearly show the possibility of substituting synthetic fertilisers with recovered NS from aquaculture waste, which can be considered an alternative and resource-efficient fertilisation strategy for soilless culture systems. Both approaches are described in this dissertation, while detailed explanations of the materials and methods used, as well as the obtained results, can be found in the appended papers.publishedVersio
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