Fermentation Wastewater Research Articles

An in-depth analysis of microbial response to exposure to high concentrations of microplastics in anaerobic wastewater fermentation

The impact of microplastics (MPs) in anaerobic wastewater treatment on microbial metabolism is significant. Anaerobic granular sludge (AS) and biofilm (BF) are two common ways, and their responses to microplastics will have a direct impact on their application potential. This study investigated the microbial reactions of AS and BF to three types of MPs: polyethylene (PE), polyvinyl chloride (PVC), and a mixture of both (MIX). Results exhibited that MPs reduced methane output by 44.65 %, 55.89 %, and 53.18 %, elevated short-chain fatty acid (SCFA) levels by 95.93 %, 124.49 %, and 110.78 %, and lowered chemical oxygen demand (COD) removal by 28.77 %, 36.78 %, and 33.99 % for PE-MP, PVC-MP, and MIX-MP, respectively, with PVC-MP showing the greatest inhibition. Meanwhile, microplastics also facilitated the relative production of reactive oxygen species (ROS, 40.29 %–96.99 %), lactate dehydrogenase (LDH, 20.01 %–75.02 %), and adenosine triphosphate (ATP, 26.64 %–43.80 %), while reducing cytochrome c (cyt c, 23.60 %–49.02 %) and extracellular polymeric substances (EPS, 17.44 %–26.58 %). AS and BF displayed distinct enzymatic activities under MPs exposure. Correspondingly, 16S-rRNA sequencing indicated that AS was mainly involved in acetate generation by Firmicutes, while BF performed polysaccharide degradation by Bacteroidota. Metatranscriptomic analysis showed AS to be rich in acetogens (Bacillus, Syntrophobacter) and methanogens (Methanothrix, Methanobacterium), while BF contained more fermentation bacteria (Mesotoga, Lentimicrobium) and electroactive microorganisms (Clostridium, Desulfuromonas) under MIX-MP. Moreover, BF exhibited higher glycolysis gene expression, whereas AS was more active in methane metabolism, primarily through the acetoclastic methanogenic pathway's direct acetate conversion. This study provides new insights into understanding the microbial response produced by microplastics during anaerobic wastewater digestion.

Membrane electrolysis distillation for volatile fatty acids extraction from pH-neutral fermented wastewater

Volatile fatty acids (VFAs) serve as building blocks for a wide range of chemicals, but it is difficult to extract VFAs from pH-neutral wastewater using evaporation methods because of the ionized form. This study presents a new membrane electrolysis distillation (MED) process that extracts VFAs from such fermentation solutions. MED uniquely integrates pH regulation and joule heating to facilitate the efficient evaporation of VFAs. This integration occurs alongside a hydrophobic membrane that ensures effective gas-liquid phase separation. Operating solely on electricity, MED achieved an acid flux rate of 12.03 g/m2/h at 6V. In contrast, the control results without the joule heating or pH swing only obtained a 0.23 g/m2/h and 0.32 g/m2/h flux, respectively. In addition, a physicochemical model was developed to assess the impacts of temperature on membrane surface pH. This system enhances resource recovery from waste streams and helps achieve a circular carbon economy.

Effect of Stepwise Exposure to High-Level Erythromycin on Anaerobic Digestion.

High-level erythromycin (ERY) fermentation wastewater will pose serious threats to lake environments. Anaerobic digestion (AD) has advantages in treating high-level antibiotic wastewater. However, the fate of antibiotic resistance genes (ARGs) and microbial communities in AD after stepwise exposure to high-level ERY remains unclear. In this study, an AD reactor was first exposed to 0, 5, 10, 50, 100 and 200 mg/L ERY and then re-exposed to 0, 50, 200 and 500 mg/L ERY to investigate the effect of ERY on AD. The results show that AD could adapt to the presence of high-level ERY (500 mg/L) and could maintain efficient CH4 production after domestication with low-level ERY (50 mg/L). The AD process could achieve higher removal of ERY (>94%), regardless of the initial ERY concentration. ErmB and mefA, conferring resistance through target alteration and efflux pumps, respectively, were dominant in the AD process. The first exposure to ERY stimulated an increase in the total ARG abundance, while the AD process seemed to discourage ARG maintenance following re-exposure to ERY. ERY inhibited the process of acetoclastic methanogenesis, but strengthened the process of hydrogenotrophic methanogenesis. This work provides useful information for treating high-level ERY fermentation wastewater by the AD process.

Fermentation of waste water from agar processing with Bacillus subtilis by metabolomic analysis.

Fungal infection has become a major threat to crop loss and affects food safety. The waste water from agar processing industries extraction has a number of active substances, which could be further transformed by microorganisms to synthesize antifungal active substances. In this study, Bacillus subtilis was used to ferment the waste water from agar processing industries extraction to analyze the antifungal activity of the fermentation broth on Alternaria alternata and Alternaria spp. Results showed that 25% of the fermentation broth was the most effective in inhibited A. alternata and Alternaria spp., with fungal inhibition rates of 99.9% and 96.1%, respectively, and a minimum inhibitory concentration (MIC) was 0.156μg/mL. Metabolomic analysis showed that flavonoid polyphenols such as coniferyl aldehyde, glycycoumarin, glycitin, and procyanidin A1 may enhance the inhibitory activity against the two pathogenic fungal strains. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that polyphenols involved in the biosynthesis pathways of isoflavonoid and phenylpropanoid were upregulated after fermentation. The laser confocal microscopy analyses and cell conductivity showed that the cytoplasm of fungi treated with fermentation broth was destroyed. This study provides a research basis for the development of new natural antifungal agents and rational use of seaweed agar waste. KEY POINTS: • Bacillus subtilis fermented waste water has antifungal activity • Bacillus subtilis could transform active substances in waste water • Waste water is a potential raw material for producing antifungal agents.

APPLICATION OF MICROBIAL FUEL CELL FOR CASSAVA FERMENTATION WASTEWATER TREATMENT

Microbial fuel cell is a new technology that utilizes bacteria as biochemicals to convert energy stored in organic/inorganic compounds, which is easily degraded into electrical energy. Apart from being able to produce electrical energy, the implementation of this technology can help solve the problem of processing wastewater resulting from cassava fermentation. The specific aim of the research is to examine the effect of cassava fermentation wastewater concentration and the effect of urea addition on the productivity of electricity produced and the reduction in the quality of cassava fermentation wastewater. From the research results, it can be concluded that the higher the cassava fermentation wastewater concentration, the smaller the electrical energy produced. The optimum initial cassava fermentation wastewater concentration is 20% v/v, with an average volumetric power density produced of 58.56 W/m<sup>3</sup>. The higher the concentration of added urea, the smaller the electrical energy produced. The optimum concentration of urea addition is 0.16-0.33 g/L. There is a linear relationship between the electricity produced and the decrease in total suspended solid (TSS) and total dissolved solid (TDS). The higher the electricity produced, indicating high bacterial activity, will cause a decrease in TSS and TDS.

Mixotrophic denitrification: A study on the removal of high nitrate concentration from piggery wastewater by biofilter reactors

The treatment of piggery wastewater through anaerobic fermentation and subsequent irrigation on farmland has been found to pose a risk of nitrate-nitrogen pollution in groundwater, thereby posing potential threats to human health. The scientific investigation of employing heterotrophic/autotrophic (mixotrophic) denitrification as a means to address the issue of farm wastewater containing elevated levels of nitrate nitrogen has garnered significant attention. This study employed sulfur monomers, limestone, and corn cob as microbial carriers within a biofilter system to facilitate the heterotrophic denitrification process of piggery wastewater fermentation broth. The efficacy of mixotrophic denitrification was found to surpass that of sulfur-limestone autotrophic denitrification in the treatment of nitrate-nitrogen wastewater with elevated concentrations of nitrate-nitrogen. This was evidenced by higher rates of denitrification, as well as reduced production of sulphate ions and alkalinity. The experiments on mixotrophic denitrification reaction observed a positive correlation between the content of corn cob and the relative abundance of microbial flora. Specifically, the relative abundance of Proteobacteria at the phylum level showed an increasing trend. Additionally, there was a proportional increase in the relative abundance of various other flora at the genus level.

Enhanced granulation of activated sludge in an airlift reactor for organic carbon removal and ammonia retention from industrial fermentation wastewater: A comparative study

Ammonia retention and recovery from high-nitrogenous wastewater are new concepts being used for nitrogen management. A microaerophilic activated sludge system was developed to convert organic nitrogen into ammonia and retain it for its recovery; however, the settleability of activated sludge remains a challenge. Therefore, this study proposed an aerobic granular sludge system as a potential solution. Two types of sequencing batch reactors—airlift and upflow reactors—were operated to investigate the feasibility of fast granule formation, the performance of organic carbon removal and ammonia retention, and the dynamics of microbial community composition. The operation fed with industrial fermentation wastewater demonstrated that the airlift reactor ensured a more rapid granule formation than the upflow reactor because of the high shear force, and it maintained a superior ammonia retention stability of approximately 85 %. Throughout the operational period, changes in hydraulic retention time (HRT), settling time, and exchange ratio altered the granular particle sizes and microbial community compositions. Rhodocyclaceae were replaced with Comamonadaceae, Methylophilaceae, Xanthomonadaceae, and Chitinophagaceae as core taxa instrumental in granulation, likely because of their extracellular polymeric substance secretion. As the granulation process progressed, a significant decrease in the relative abundances of nitrifying bacteria—Nitrospiraceae and Nitrosomonadaceae—was observed. The reduction of settling time and HRT enhanced granulation and inhibited the activity of nitrifying bacteria. The success in granulation for ammonia conversion and retention in this study accelerates the paradigm shift from ammonia removal to ammonia recovery from industrial fermentation wastewater.

Polyhydroxyalkanoates production in purple phototrophic bacteria ponds: A breakthrough in outdoor pilot-scale operation

The versatile capacity of purple phototrophic bacteria (PPB) for producing valuable bioproducts has gathered renewed interest in the field of resource recovery and waste valorisation. However, greater knowledge regarding the viability of applying PPB technologies in outdoor, large-scale systems is required. This study assessed, for the first time, the upscaling of the phototrophic polyhydroxyalkanoate (PHA) production technology in a pilot-scale system operated in outdoor conditions. An integrated system composed of two up-flow anaerobic sludge blanket (UASB) reactors (for fermentation of wastewater with molasses), and two high-rate algal ponds retrofitted into PPB ponds, was operated in a wastewater treatment plant under outdoor conditions. UASB's adaptation to the outdoor temperatures involved testing different operational settings, namely hydraulic retention times (HRT) of 48 and 72 h, and molasses fermentation in one or two UASBs. Results have shown that the fermentation of molasses in both UASBs with an increased HRT of 72 h was able to ensure a suitable operation during colder conditions, achieving 3.83 ± 0.63 g CODFermentative Products/L, compared to the 3.73 ± 0.85 g CODFermentative Products/L achieved during warmer conditions (molasses fermentation in one UASB; HRT 48 h). Furthermore, the PPB ponds were operated under a light-feast/dark-aerated-famine strategy and fed with the fermented wastewater and molasses from the two UASBs. The best PHA production was obtained during the summer of 2018 and spring of 2019, attaining 34.7 % gPHA/gVSS with a productivity of 0.11 gPHA L−1 day−1 and 36 % gPHA/gVSS with a productivity of 0.14 gPHA L−1 day−1, respectively. Overall, this study showcases the first translation of phototrophic PHA production technology from an artificially illuminated laboratory scale system into a naturally illuminated, outdoor, pilot-scale system. It also addresses relevant process integration aspects with UASBs for pre-fermenting wastewater with molasses, providing a novel operational strategy to achieve photosynthetic PHA production in outdoor full-scale systems.

Overlooked abiotic humification for kanamycin removal in kanamycin fermentation waste by tea polyphenols: New, environmentally friendly and specific

Kanamycin, a typical aminoglycoside antibiotic, is mainly used for the treatment of diseases in humans or animals, while the related antibiotic pollution has been regarded as a serious issue. In this study, a green novel approach to remove kanamycin was established, specifically, kanamycin was specifically removed through abiotic humification process with tea polyphenols (TPs) as the polyphenol donor. The results demonstrated that the kanamycin could be effectively removed by TPs under alkaline conditions, with a 99.9 % highest removal efficiency. Among the three factors (pH, temperature and MnO2 dosage) selected in this study, pH was the most critical factor, with an increase in reaction pH (>6.0) leading to a higher kanamycin removal efficiency, and the temperature and MnO2 dosage ranked as the second and third important factor. Furthermore, kanamycin was mainly removed by being transformed into humic-like acid (HLA) product, and the product antimicrobial activity could be significantly reduced (≥27). Finally, satisfying removal efficiency of kanamycin were observed during the application of TPs in kanamycin fermentation wastewater and kanamycin mycelial residue (KMR), with the highest kanamycin removal efficiency was 99.9 %, and 99.6 %, respectively. This study could also offer insights for the removal of other pollutants containing primary amine or polyphenols.

Yeast Lipids from Crude Glycerol Media and Utilization of Lipid Fermentation Wastewater as Maceration Water in Cultures of Edible and Medicinal Mushrooms

Four wild “red” yeast strains (Rhodosporidium kratochvilovae FMCC Y70, R. toruloides NRRL Y-27013, R. toruloides NRRL Y-17902 and R. toruloides NRRL Y-6985) were cultured in shake flasks on industrial glycerol at an initial substrate (Gly0) concentration ≈ 50 g/L under nitrogen limitation. Strains NRRL Y-27013, NRRL Y-17902 and NRRL Y-6985 presented appreciable dry cell weight (DCW) and lipid synthesis (DCW up to 18–19 g/L containing lipids in quantities ≈ 47%, w/w). Strains NRRL Y-27013 and NRRL Y-6985 were further tested in higher Gly0 concentrations (≈90 g/L and ≈110 g/L) with the same initial nitrogen quantity as in the first (“screening”) experiment. Both strains, despite the high Gly0 concentrations and C/N ratios (up to 120 moles/moles) imposed, presented significant DCW production (up to c. 29.0–29.5 g/L). Yeast biomass contained significant lipid (42–43%, w/w) and endopolysaccharide (up to 42%, w/w) quantities. Both lipids and endopolysaccharide quantities (in % w/w) noticeably increased as a response to the imposed nitrogen limitation. Lipids containing mainly oleic and palmitic acids constituted ideal candidates for biodiesel synthesis. Thereafter, the wastewaters derived from the lipid production process (lipid fermentation wastewaters—LFWs) were used as maceration waters in cultivations of edible and medicinal fungi, where novel (non-conventional) substrates were used in the performed cultures. CW (coffee residue + wheat straw), CB (coffee residue + beech wood shavings), OW (olive crop + wheat straw), OB (olive crop + beech wood shavings), RW (rice husk + wheat straw) and RB (rice husk + beech wood shavings) were soaked/sprayed with LFWs or tap water and utilized in the cultivation of Pleurotus, Ganoderma and Lentinula mushrooms. The impact of LFWs on the mycelial growth rate (mm/d) and biomass production was evaluated. The results show that regardless of the wetting method, the highest growth rates (6.2–6.6 mm/d) were noticed on RW and RB for Pleurotus eryngii and Ganoderma resinaceum, on OW, OB and RW for Ganoderma applanatum and on RW, OW and OB for Lentinula edodes. Nevertheless, high biomass production was obtained on substrates soaked with LFWs for Pleurotus ostreatus (RW: 443 mg/g d.w.), L. edodes (RB: 238 mg/g d.w.) and Ganoderma lucidum (RW: 450 mg/g d.w.). Overall, this study demonstrates the possibility of the industrial conversion of low-value agro-waste to mycelial mass and eventually to important food products.

Yeast-driven valorization of agro-industrial wastewater: an overview.

The intensive industrial and agricultural activities currently on-going worldwide to feed the growing human population have led to significant increase in the amount of wastewater produced. These effluents are high in phosphorus (P), nitrogen (N), chemical oxygen demand (COD), biochemical oxygen demand (BOD), and heavy metals. These compounds can provoke imbalance in the ecosystem with grievous consequences to both the environment and humans. Adequate treatment of these wastewaters is therefore of utmost importance to humanity. This can be achieved through valorization of these waste streams, which is based on biorefinery idea and concept of reduce, reuse, and recycle for sustainable circular economy. This concept uses innovative processes to produce value-added products from waste such as wastewater. Yeast-based wastewater treatment is currently on the rise given to the many characteristics of yeast cells. Yeasts are generally fast growing, and they are robust in terms of tolerance to stress and inhibitory compounds, in addition to their ability to metabolize a diverse range of substrates and create a diverse range of metabolites. Therefore, yeast cells possess the capacity to recover and transform agro-industrial wastewater nutrients into highly valuable metabolites. In addition to remediating the wastewater, numerous value-added products such as single cell oil (SCO), single cell proteins (SCPs), biofuels, organic acid, and aromatic compounds amongst others can be produced through fermentation of wastewater by yeast cells. This work thus brings to limelight the potential roles of yeast cells in reducing, reusing, and recycling of agro-industrial wastewaters while proffering solutions to some of the factors that limit yeast-mediated wastewater valorization.

Quorum sensing in different subcommunities becomes the key factor affecting the humification of the aerobic composting system with sauerkraut fermentation wastewater

Aerobic composting is an effective and harmless method to treat Sauerkraut fermentation wastewater (SFW). Given the limited understanding of the effect of quorum sensing (QS) on humification in subcommunities under acidic environments, a large-scale analysis was conducted to identify features that impact the response of QS to humification in different subcommunities. The results showed that the addition of SFW directly affected humification in subcommunities A and C, and the abundances of functional genes related to carbon fixation and carbon degradation were significantly increased at 7 and 15 d, respectively. In addition, subcommunity B indirectly affected humus production but regulated carbon metabolic pathways such as glycolysis/gluconeogenesis and pentose phosphate by QS with subcommunities B. These findings provide a novel perspective for analysing the regulation of humification in aerobic composting and suggest that composting has potential applications in organic wastewater treatment.

Adsorptive recovery of volatile fatty acids from wastewater fermentation broth

This work developed an adsorptive separation and recovery process for anaerobically generated volatile fatty acids (VFAs) from swine wastewater fermentation. Batch adsorption studies were conducted using several weak anion exchange resins and synthetic adsorbent resins to identify a suitable candidate. Relite RAM2 with a tertiary amine functional group showed the highest adsorption (over 98%) of hexanoic acid. Under the different pH values (1.8–7.5) and extraction temperatures (30–50 °C), the highest adsorption was observed at a pH of 3.2, which is below the pKa of hexanoic acid, at all the evaluated temperatures. A full factorial design was used to optimize the resin and VFA concentrations, wherein over 99% adsorption could be achieved when the ratio of VFA to resin was below 0.23 (g/g) for model solution (VFAs in water). The adsorption equilibrium could be achieved within 30 min of contact time and 0.5% w/v NaOH was identified as a suitable desorption agent. Under the optimal conditions, 65–72% of VFAs present in fermentation broth was adsorbed, which was increased to 72–76% by using fresh resins. The VFAs adsorption and recovery efficiency were maintained for 9 successive cycles without requiring extensive resin washing and regeneration for both model solution and fermentation broth. Overall, the work presents a comprehensive study for resin adsorption to recover VFAs and provides a potential industrial-relevant process to recover VFAs from fermentation broth.

Development of a green fermentation strategy with resource cycle for the docosahexaenoic acid production by Schizochytrium sp.

The fermentation production of docosahexaenoic acid (DHA) is an industrial process with huge consumption of freshwater resource and nutrient, such as carbon sources and nitrogen sources. In this study, seawater and fermentation wastewater were introduced into the fermentation production of DHA, which could solve the problem of fermentation industry competing with humans for freshwater. In addition, a green fermentation strategy with pH control using waste ammonia, NaOH and citric acid as well as FW recycling was proposed. It could provide a stable external environment for cell growth and lipid synthesis while alleviating the dependence on organic nitrogen sources of Schizochytrium sp. It was proved that this strategy has good industrialization potential for DHA production, and the biomass, lipid and DHA yield reached to 195.8 g/L, 74.4 g/L and 46.4 g/L in 50 L bioreactor, respectively. This study provides a green and economic bioprocess technology for DHA production by Schizochytrium sp.

Ultrasound-controlled acidogenic valorization of wastewater for biohydrogen and volatile fatty acids production: Microbial community profiling

The present study explored the influence of ultrasound on acidogenic fermentation of wastewater for the production of biohydrogen and volatile fatty acids/carboxylic acids. Eight sono-bioreactors underwent ultrasound (20kHz: 2W and 4W), with an ultrasound duration ranging from 15min to 30days, and the formation of acidogenic metabolites. Long-term continuous ultrasonication enhanced biohydrogen and volatile fatty acid production. Specifically, ultrasonication at 4W for 30days increased biohydrogen production by 3.05-fold compared to the control, corresponding to hydrogen conversion efficiency of 58.4%; enhanced volatile fatty acid production by 2.49-fold; and increased acidification to 76.43%. The observed effect of ultrasound was linked to enrichment with hydrogen-producing acidogens such as Firmicutes, whose proportion increased from 61.9% (control) to 86.22% (4W, 30days) and 97.53% (2W, 30days), as well as inhibition of methanogens. This result demonstrates the positive effect of ultrasound on the acidogenic conversion of wastewater to biohydrogen and volatile fatty acid production.

Volatile Fatty Acids Production by Acidogenic Fermentation of Wastewater: A Bibliometric Analysis

This study presents a bibliometric analysis of the scientific literature on volatile fatty acids (VFA) production from wastewater fermentation published from 1981 to 21 June 2021. A total of 618 papers obtained from the Scopus database were analyzed using VOSviewer 1.6.16 software. According to the results, this topic has been capturing the attention of researchers over the years, but with different research approaches, including optimization of anaerobic digestion in two-stage reactors, biological removal of nutrients from wastewater, energy production in bioelectrochemical systems, and recovery of VFA as value-added intermediate products to be used as inputs in a variety of industries. In addition, the bibliometric networks obtained from the authors’ keyword frequency showed that wastewater treatment by using fermentation to obtain VFA as a value-added by-product is an emerging topic that undoubtedly requires further research and collaboration between scientific institutions. In this regard, different types of wastewater have been used as a substrate for acidogenic fermentation; however, and based on the results, the production of VFA from cassava processing wastewater is seen as one of the emerging issues of this field. Finally, evaluating the effect of operating conditions on the fermentation process, such as pH, hydraulic retention time, organic loading rate, temperature, inoculum and substrate concentration, independent of the final application of the VFA produced, is a relevant aspect for bioprocess optimization and implementation on a large scale.

Survival strategies of Nitrospira in a stable nitritation-denitritation system treating low-strength fermented wastewater

Mainstream nitritation and denitritation can save aeration energy and carbon sources, but it is difficult to eliminate nitrite-oxidizing bacteria. Except for nitrite oxidation, Nitrospira may benefit from mixotrophic lifestyles. In our previous study, stable NOB suppression was achieved in a multi-cycle sequencing batch reactor (MCSBR) treating fermented low-strength wastewater. However, abundant Nitrospira was always detected, which was contrary to the negligible nitrate accumulation. Batch tests indicated that only acetate could be consumed by the enriched Nitrospira within six hours. In another batch test within six days, nitrate was fully or partially denitrified to nitrite after adding formate or acetate, while Nitrospira decreased 86.5 % and 28.7 % respectively. After adding formate, two hydrogenotrophic denitrifiers Hydrogenophaga and Methyloversatilis highly proliferated, but only Hydrogenophaga was also found in the MCSBR. Therefore, Nitrospira might still grow through nitrite oxidation, while the generated nitrate was timely reduced by Hydrogenophaga in the presence of simple organic carbons, or directly survived by heterotrophic acetate metabolism.

Bio-hydrogen production by dark anaerobic fermentation of organic wastewater.

Using organic wastewater to produce hydrogen by fermentation can generate clean energy while treating wastewater. At present, there are many inhibitory factors in the hydrogen production process, resulting in unsatisfactory hydrogen yield and hydrogen concentration during the fermentation process, and there are still great obstacles to the industrial promotion and commercial application of organic wastewater fermentation hydrogen production. This paper summarizes the hydrogen production of organic wastewater dark anaerobic fermentation technology. The current anaerobic fermentation hydrogen production systems and technologies are summarized and compared, and the factors and potential conditions that affect the performance of hydrogen production are discussed. The further requirements and research priorities for the market application of fermentation biohydrogen production technology in wastewater utilization are prospected.

Suitability of pre-digested dairy effluent for mixotrophic cultivation of the hydrogen-producing microalgae Tetraselmis subcordiformis

ABSTRACT The costs associated with microalgal biomass production can be reduced by leveraging alternative and cheap growth media. Digestate from fermentation reactors is a particularly interesting candidate for use in cultivating mixotrophic species. The aim of the present study was to assess whether pre-digested milk-industry effluent can be harnessed to grow Tetraselmis subcordiformis and produce hydrogen. The experimental series with 25% and 50% effluent in the growth medium performed the best, producing more than 2000 mgVS biomass/dm3. The biogas produced in these variants contained over 60% hydrogen. Increasing the effluent in the medium to 75% led to significant deterioration of performance, both in terms of T. subcordiformis biomass growth and biohydrogen production. The highest efficiency of nitrogen and phosphorus removal, respectively 98.1 ± 1.9% and 97.1 ± 1.4%, was observed in the system to which 25% of sewage was introduced. Increasing the share of fermented wastewater directly reduced the efficiency of removing biogenic compounds. A very strong negative correlation was found between initial N-NH4 in the growth medium and T. subcordiformis biomass production rates (R2 = 0.9177).

ANAEROBIC BIOLOGICAL WASTEWATER TREATMENT OF SUGAR PRODUCTION

Water usage of sugar beet factories is characterized by a high level of consumption and a large volume of generated wastewater with a high concentration of mineral and organic pollution. Artificial biological purification facilities are mainly used for purification of sugar production effluents. While a scheme with two-stage aeration tanks is the most widespread in our country,anaerobic-aerobic regimens are frequently used abroad. It is more cost-effective, since the oxidation of large amounts of organic substances exclusively under aerobic conditions is associated with high energy consumption. The use of anaerobic digestion at the first stage allows reducing the concentration of organic substances in effluents by 60-90%, while the post-purification of remaining contaminants is carried out in stage-two aeration tanks with lower energy consumption. To assess the appropriateness of using a digester in the system of purification facilities of a particular enterprise, it is necessary to have information on the effectiveness of digestion and the optimal purification regime of the wastewater of that particular enterprise. This work studies the process of anaerobic digestion of wastewater at one of the beet sugar factories in Ukraine. The experiments were carried out in a bioreactor with an upward flow of activated sludge. The method of mathematical planning of an experiment was used in order to shorten the duration of the research. As a result, data was obtained regarding the influence of determining factors (flow rate, pH, temperature) on biogas yield and substrate fermentation depth. Received data proves the effectiveness and prospects of using anaerobic digestion in the first stage of biological fermentation of wastewater at a sugar beet production.