Electron donors for autotrophic denitrification Di Capua, Francesco; Pirozzi, Francesco; Lens, Piet N.L. ...
Chemical engineering journal (Lausanne, Switzerland : 1996),
04/2019, Letnik:
362
Journal Article
Recenzirano
Display omitted
•Twelve electron donors for autotrophic denitrification are critically reviewed.•Biochemical aspects and microbiology of autotrophic denitrification are discussed.•Novel insights on ...the use of inorganic compounds for denitrification are presented.•Applications, cost and environmental impact of inorganic compounds are compared.•Criteria and guidelines for electron donor selection are provided.
Autotrophic denitrification (AuDen) is an efficient, convenient and eco-friendly biological process for the treatment of nitrate-contaminated organic-deficient waters. AuDen can be applied as a unique process or complement the conventional denitrification with organics, reducing the risk of organic carbon breakthrough in the effluent and formation of undesirable byproducts downstream (e.g. trihalomethanes). A wide range of inorganic compounds can act as electron donors for AuDen. The most used electron donors include hydrogen gas and reduced sulfur compounds, i.e. elemental sulfur, sulfide and thiosulfate. Recently, the denitrification potential of certain contaminants (such as sulfite, thiocyanate, arsenite and manganese) and inorganic wastes (such as biogenic elemental sulfur from biogas upgrading) has been revealed and attracted interest for developing technologies that combine nitrate removal with water detoxification. This paper critically reviews the state of the art of the most used electron donors for AuDen and highlights recent advances on the application of novel inorganic compounds, reactor configurations and microorganisms to support denitrification. Criteria and guidelines for the selection of a suitable electron donor are provided.
•Pretreating organic solid wastes leads to an enhanced anaerobic digestion process.•Pretreatments may also reduce the cost for post treatment of digestates.•Efficiency of pretreatment methods depends ...on the substrates’ characteristics.•Only few pretreatment methods are successfully applied at full-scale to date.
This paper reviews pretreatment techniques to enhance the anaerobic digestion of organic solid waste, including mechanical, thermal, chemical and biological methods. The effects of various pretreatment methods are discussed independently and in combination. Pretreatment methods are compared in terms of their efficiency, energy balance, environmental sustainability as well as capital, operational and maintenance costs. Based on the comparison, thermal pretreatment at low (<110°C) temperatures and two-stage anaerobic digestion methods result in a more cost-effective process performance as compared to other pretreatment methods.
Display omitted
•Comparative analysis of biofilm reactors for chemolithotrophic denitrification.•Water characteristics strongly affect the bioreactor denitrification performance.•A decision tool for ...choosing the most appropriate bioreactor is provided.•Fluidized bed and membrane biofilm reactors have the highest denitrification rates.•Packed bed and biofilm electrode reactors are cost-effective alternatives.
Chemolithotrophic denitrification is an inexpensive and advantageous process for nitrate removal and represents a promising alternative to classical denitrification with organics. Chemolithotrophic denitrifiers are microorganisms able to reduce nitrate and nitrite using inorganic compounds as source of energy. Ferrous iron, sulfur-reduced compounds (e.g. hydrogen sulfide, elemental sulfur and thiosulfate), hydrogen gas, pyrite and arsenite have been used as inorganic electron donors resulting in diverse outcomes. In the last 40years, a large number of engineered systems have been used to maintain chemolithotrophic denitrification and improve rate and efficiency of the process. Among them, biofilm reactors proved to be robust and high-performing technologies. Packed bed reactors are particularly suitable for the removal of low nitrate concentrations, since high retention times are required to complete denitrification. Fluidized bed and membrane biofilm reactors result in the highest denitrification rates (>20kg N-NO3−/m3d) when hydrogen gas and sulfur reduced compounds are used as electron donors. Hydrogen gas pressure and current intensity rule the performance of membrane biofilm and biofilm electrode reactors, respectively. Biofouling is the most common and detrimental issue in biofilm reactors. Bed fluidization and hydrogen supply limitation are convenient and effective solutions to mitigate biofouling.
Electrochemical degradation of aqueous solutions containing antibiotic amoxicillin (AMX) has been extensively studied in an undivided electrolytic cell using a sub-stoichiometric titanium oxide ...(Ti4O7) anode, elaborated by plasma deposition. Oxidative degradation of AMX by hydroxyl radicals was assessed as a function of applied current and was found to follow pseudo-first order kinetics. The use of carbon-felt cathode enhanced oxidation capacity of the process due to the generation of H2O2. Comparative studies at low current intensity using dimensional stable anode (DSA) and Pt anodes led to the lower mineralization efficiencies compared to Ti4O7 anode: 36 and 41% TOC removal for DSA and Pt respectively compared to 69% for Ti4O7 anode. Besides, the use of boron doped diamond (BDD) anode under similar operating conditions allowed reaching higher mineralization (94%) efficiency. Although Ti4O7 anode provides a lesser mineralization rate compared to BDD, it exhibits better performance compared to the classical anodes Pt and DSA and can constitutes an alternative to BDD anode for a cost effective electro-oxidation process. Moreover several aromatic and aliphatic oxidation reaction intermediates and inorganic end-products were identified and a plausible mineralization pathway of AMX involving these intermediates was proposed.
Display omitted
•Ti4O7 anode prepared by plasma deposition on titanium (Ti) substrate.•Degradation and mineralization efficiency increases with increased applied current.•Better mineralization efficiency with Ti4O7 compared to DSA and Pt anodes.•Very good oxidation efficiency of Ti4O7 close to that of BDD anode.•H2O2 enhances degradation but has marginal effect on mineralization of amoxicillin.
Stormwater runoff is often contaminated by human activities. Stormwater discharge into water bodies significantly contributes to environmental pollution. The choice of suitable treatment technologies ...is dependent on the pollutant concentrations. Wastewater quality indicators such as biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), and total dissolved solids (TDS) give a measure of the main pollutants. The aim of this study is to provide an indirect methodology for the estimation of the main wastewater quality indicators, based on some characteristics of the drainage basin. The catchment is seen as a black box: the physical processes of accumulation, washing, and transport of pollutants are not mathematically described. Two models deriving from studies on artificial intelligence have been used in this research: Support Vector Regression (SVR) and Regression Trees (RT). Both the models showed robustness, reliability, and high generalization capability. However, with reference to coefficient of determination R2 and root-mean square error, Support Vector Regression showed a better performance than Regression Tree in predicting TSS, TDS, and COD. As regards BOD5, the two models showed a comparable performance. Therefore, the considered machine learning algorithms may be useful for providing an estimation of the values to be considered for the sizing of the treatment units in absence of direct measures.
This paper reviews the formation, structure, and stability of bioaggregates with an emphasis on the composition and distribution of extracellular polymeric substances (EPS) and their role in ...bioaggregation. Bioaggregation is ubiquitous in natural environment and is of great importance in biological wastewater treatment processes. It greatly influences the flocculability, settleability, and dewaterability for flocs and sludge retention and shear resistance for biofilms. The physico-chemical and microbial structures of bioaggregates are dependent on operational conditions as well as microbial diversity and spatial distribution. The formation of bioaggregates is mediated by the physico-chemical interactions as well as the microbial interactions such as EPS production and quorum sensing. EPS are composed of a mixture of macromolecules including proteins, polysaccharides, humic-like substances, and nucleic acids, which entrap the microbial cells in a three-dimensional matrix. The composition and physico-chemical characteristics of EPS have significant influence on the maintenance of the bioaggregate structure and the process performance of the wastewater treatment. However, the mechanisms of bioaggregation are still unclear and the conclusions on the role of EPS were mostly drawn from the established correlations and hypotheses. This paper expects to provide up-to-date knowledge on bioaggregation and insights for further studies and applications.
Parkinson’s disease patients report disturbed sleep patterns long before motor dysfunction. Here, in parkin and pink1 models, we identify circadian rhythm and sleep pattern defects and map these to ...specific neuropeptidergic neurons in fly models and in hypothalamic neurons differentiated from patient induced pluripotent stem cells (iPSCs). Parkin and Pink1 control the clearance of mitochondria by protein ubiquitination. Although we do not observe major defects in mitochondria of mutant neuropeptidergic neurons, we do find an excess of endoplasmic reticulum-mitochondrial contacts. These excessive contact sites cause abnormal lipid trafficking that depletes phosphatidylserine from the endoplasmic reticulum (ER) and disrupts the production of neuropeptide-containing vesicles. Feeding mutant animals phosphatidylserine rescues neuropeptidergic vesicle production and acutely restores normal sleep patterns in mutant animals. Hence, sleep patterns and circadian disturbances in Parkinson’s disease models are explained by excessive ER-mitochondrial contacts, and blocking their formation or increasing phosphatidylserine levels rescues the defects in vivo.
Display omitted
•Parkinson’s disease (PD) models (parkin/pink1 loss) have circadian and sleep defects•Increased ER-mitochondria contacts cause neuropeptide accumulation in ER in PD models•Depletion of phosphatidylserine from ER causes sleep pattern phenotypes in PD models•Phosphatidylserine supplementation rescues circadian and sleep defects of PD models
Valadas et al. show that ER lipid imbalance causes sleep pattern defects in Parkinson’s disease by preventing the formation of secretory vesicles required for the release of the neuropeptides. Restoring the ER lipid balance by supplementation with phosphatidylserine rescues the cellular and behavioral defects.
Cheese whey (CW) and hemp hurds (HH) represent typically overabundant biowastes of food and agricultural production, and their circular management is crucial to improve both sustainability and ...profitability of the agri-food chain. By combining experimental biochemical methane potential (BMP) tests and literature data, the techno-economic aspects of a possible future bioenergy valorization of CW and HH through anaerobic digestion (AD) and co- digestion (coAD) were analyzed. Along the 42-days, BMP assays, CW, and HH alone rendered BMP values of 446 ± 66 and 242 ± 13 mL CH4·g VS−1, respectively. The application of coAD with CW and HH at a 70:30 ratio allowed to enhance the biomethane production by 10.7%, as compared to the corresponding calculated value. In terms of economic profitability, the valorization of HH as biomethane in a dual-purpose hemp cultivation could potentially enable net profits of up to 3929 €·ha−1, which could rise to 6124 €·ha−1 in case of coAD with CW. Finally, by projecting the biomethane potential from current and future available CW and HH residues in the national context of Italy, a total biomethane yield of up to 296 MNm3·y−1 could be attained, offering interesting perspectives for the sustainability of key sectors such as transportation.
The world is currently witnessing a rapid increase in sewage sludge (SS) production, due to the increased demand for wastewater treatment. Therefore, SS management is crucial for the economic and ...environmental sustainability of wastewater treatment plants. The recovery of nutrients from SS has been identified as a fundamental step to enable the transition from a linear to a circular economy, turning SS into an economic and sustainable source of materials. SS is often treated via anaerobic digestion, to pursue energy recovery via biogas generation. Anaerobically digested sewage sludge (ADS) is a valuable source of organic matter and nutrients, and significant advances have been made in recent years in methods and technologies for nutrient recovery from ADS. The purpose of this study is to provide a comprehensive overview, describing the advantages and drawbacks of the available and emerging technologies for recovery of nitrogen (N), phosphorus (P), and potassium (K) from ADS. This work critically reviews the established and novel technologies, which are classified by their ability to recover a specific nutrient (ammonia stripping) or to allow the simultaneous recovery of multiple elements (struvite precipitation, ion exchange, membrane technologies, and thermal treatments). This study compares the described technologies in terms of nutrient recovery efficiency, capital, and operational costs, as well as their feasibility for full-scale application, revealing the current state of the art and future perspectives on this topic.
Industrial hemp stands out as a promising candidate for clean and sustainable biomass-to-bioenergy systems due to its multipurpose, high biomass yield and resource efficiency features. In this study, ...different hemp biomass residues (HBRs) were evaluated as a potential feedstock for renewable biomethane production through anaerobic digestion (AD). The biochemical methane potential (BMP) of the raw and pretreated fibers, stalks, hurds, leaves and inflorescences was investigated by means of batch anaerobic tests. The highest BMP was obtained with the raw fibers (i.e., 422 ± 20 mL CH4·g VS−1), while hemp hurds (unretted), making up more than half of the whole hemp plant dry weight, showed a lower BMP value of 239 ± 10 mL CH4·g VS−1. The alkali pretreatment of unretted hurds and mechanical grinding of retted hurds effectively enhanced the BMP of both substrates by 15.9%. The mix of leaves and inflorescences and inflorescences alone showed low BMP values (i.e., 118 ± 8 and 26 ± 5 mL CH4·g VS−1, respectively) and a prolonged inhibition of methanogenesis. The latter could be overcome through NaOH pretreatment in the mix of leaves and inflorescences (+28.5% methane production).
PDF
