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Urea is the most common nitrogen (N) fertilizer in agriculture, due to its cheaper price and high N content. Although the reciprocal influence between NO3- and NH4+ nutrition are well known, urea (U) interactions with these N-inorganic forms are poorly studied. Here, the responses of two tomato genotypes to ammonium nitrate (AN), U alone or in combination were investigated. Significant differences in root and shoot biomass between genotypes were observed. Under AN+U supply, Linosa showed higher biomass compared to UC82, exhibiting also higher values for many root architectural traits. Linosa showed higher Nitrogen Uptake (NUpE) and Utilization Efficiency (NUtE) compared to UC82, under AN+U nutrition. Interestingly, Linosa exhibited also a significantly higher DUR3 transcript abundance. These results underline the beneficial effect of AN+U nutrition, highlighting new molecular and physiological strategies for selecting crops that can be used for more sustainable agriculture. The data suggest that translocation and utilization (NUtE) might be a more important component of NUE than uptake (NUpE) in tomato. Genetic variation could be a source for useful NUE traits in tomato; further experiments are needed to dissect the NUtE components that confer a higher ability to utilize N in Linosa.

Anode with good electrocatalytic capabilities is more specifically required to reduce the ohimic losses during microbial fuel cell (MFC) operation. Highly conductive polymers viz., Polyaniline (PANi) and Polyaniline/Carbon nanotube (PANi/CNT) composite were prepared by in situ oxidative chemical polymerization method. Anodes were fabricated independently by coating PANi and CNT/PANi composites on the surface of SSM. The fabricated electrodes were evaluated as anode against stainless steel mess (SSM) as cathode during MFC operation. Maximum bioelectricity generation was observed in SSM-PANi/CNT-anode with power density of 48 mW/m2 and COD removal efficiency of 80% compared with SSM-PANi-anode (38 mW/m2; 65%) and SSM-anode (28 mW/m2; 58%). Bioelectrochemical characterization of the electrode materials using cyclic voltammetry and electrochemical impedance spectroscopy showed high electrocatalytic activity of PANi/CNT composite electrode. The study concluded the efficiency of PANi/CNT composite electrodes as bioanode in operation of MFCs towards achieving increased bioelectricity production along with wastewater treatment.

Microbial electrochemical technologies (METs) constitute the core of a number of emerging technologies with a high potential for treating urban wastewater due to a fascinating reaction mechanism—the electron transfer between bacteria and electrodes to transform metabolism into electrical current. In the current work, we focus on the model electroactive microorganism Geobacter sulfurreducens to explore both the design of new start-up procedures and electrochemical operations. Our chemostat-grown plug and play cells, were able to reduce the start-up period by 20-fold while enhancing chemical oxygen demand (COD) removal by more than 6-fold during this period. Moreover, a filter-press based bioreactor was successfully tested for both acetate-supplemented synthetic wastewater and real urban wastewater. This proof-of-concept pre-pilot treatment included a microbial electrolysis cell (MEC) followed in time by a microbial fuel cell (MFC) to finally generate electrical current of ca. 20 A·m−2 with a power of 10 W·m−2 while removing 42 g COD day−1·m−2. The effective removal of acetate suggests a potential use of this modular technology for treating acetogenic wastewater where Geobacter sulfurreducens outcompetes other organisms.

AbstractPhosphorus (P) accumulators used for phytoremediation vary in their potential to acquire P from different high P regimes. Growth and P accumulation in Polygonum hydropiper were both dependent on an increasing level of IHP (1–8 mM P) and on a prolonged growth period (3-9 weeks) and those of the mining ecotype (ME) were higher than the non-mining ecotype (NME). Biomass increments in root, stem and leaf of both ecotypes were significantly greater in IHP relative to other organic P (Po) sources (G1P, AMP, ATP), but lower than those in inorganic P (Pi) treatment (KH2PO4). P accumulation in the ME exceeded the NME from different P regimes. The ME demonstrated higher root activity compared to the NME grown in various P sources. Acid phosphatase (Apase) and phytase activities in root extracts of both ecotypes grown in IHP were comparable to that in Pi, or even higher in IHP. Higher secreted Apase and phytase activities were detected in the ME treated with different P sources relative to the NME. Therefore, the ME demonstrates higher P-uptake efficiency and it is a potential material for phytoextraction from P contaminated areas, irrespective of Pi or Po contamination.

AbstractSlaughterhouses generate highly polluted effluents, and if not treated before discharge can cause major adverse environmental and public health impacts. Treatment of this waste by anaerobic digestion can reduce those impacts while producing a potentially valuable source of energy. The purpose of this study was to investigate this process efficiency under pilot operating conditions for a more accurate scaling up. Blood waste from a slaughterhouse was treated in a pilot‐scale digester of 30 dm3 total volume under mesophilic temperature conditions. Operating parameters such as pH, alkalinity, organic loading, volatile fatty acids, biogas composition, total and volatile solids were monitored in order to study the behavior of the fermentation process. The results show that no significant inhibition were caused by the accumulation of volatile fatty acids, due to the high buffering capacity of treated sludge. An efficient reduction of organic matter was obtained with a COD decrease of about 67% within 40 days of fermentation. The biogas produced was of a good quality with high CH4 yields (above 70%) and low CO2 yields, corresponding to a biomethane potential of 225.9 dm3 CH4/kg TVS. Logistic model described accurately the methane production kinetic and enables an easy process scaling up for industrial applications.

Microbial fuel cell (MFC) has received much attention in the last decade as a promising technology to simultaneously generate electricity and decontaminate wastewater. This study aims to quantitatively review the published literature on MFC, published in the period of 1970–2020, based on the Web of Science (WoS) database. For the first time in literature, a comprehensive quantitative review of MFC has been conducted by employing the technique of bibliometric and content analyses. A total of 11,397 publications have been retrieved from WoS, out of which 81.6% are research articles. The evaluation in the field of MFC has been mapped in various categories, such as publication history, publication distribution, subject category distribution, leading journals, leading countries and leading organizations in MFC research. Additionally, content analysis has been conducted to unearth the research trends in MFC; and some hot research topics in MFC have been spotted. Results depict that the period 2011–2020 has been the most appreciating era for MFC research, as it contributed 87% of the total publications. Among the subject categories, energy fuel and microbiology lead with contributions of 26.5% for each, butthe overall growth of the energy fuel category in the last decade has been the highest. Out of 1,147 journals publishing MFC research, Bioresource Technology is the leading one; and countries like China, USA and India are the main hub of MFC research with 26.47%, 16.95% and 7.69% contributions in publications, respectively. The hottest topics in MFC research are nanoparticles, catalysts, air electrodes, graphene electrodes, power enhancement, air cathode and nitrogen removal. Moreover, major research areas are engineering, energy fuels and biotechnology with each contribution 26.5% of the total publications.

With respect to the ecological relevance of endpoints, biomass as an endpoint might be promising regarding ecotoxicological assessments of benthic communities. In a freshwater microcosm study the effect of two cadmium (Cd) concentrations (50 and 400 mg Cd kg(-1) dw) on biomass and abundance of a benthic community were investigated over a period of seven months. Specifically, the sensitivity of both endpoints in distinguishing differential effects was compared. While bacteria were found to be unaffected by Cd, abundance and biomass of protozoans and metazoans decreased. In a short-term comparison, differences between control and Cd treatments were, overall, more pronounced for flagellate biomass and for metazoan abundance with strong differences between the taxonomic groups; furthermore, over the long-term, the differences among organisms and endpoints changed. Based on toxicant sensitivity, the reasonably low variance of the data and the workload involved, biomass can provide a useful additional endpoint in microcosm studies.

Wastewater containing ammonia nitrogen compounds is considered as a harmful material to environment due to eutrophication and toxicity effects; hence, finding practical methods for treating this type of wastewater seems necessary. In this study, performance of two sequencing batch reactors have been assessed for simultaneous nitrification and denitrification in treating synthesized wastewater containing ammonium nitrogen, using leachate obtained from cow dung as the biomass. The leachate obtained from cow dung as the source of bio‐sludge added to the reactors. Experiments were designed according to central composition design and response surface methodology with four operating variables including pH (6, 7.5, 9), cycle time (CT) (4, 12, 20 h), ratio (5, 10, 15) and carbon source (Sodium acetate: , Glucose: ). According to statistical analysis, experimental responses were in acceptable agreement with model predictions. CT was the most important operating variable in chemical oxygen demand (COD) and removal. The maximum percentage of ammonium nitrogen removal was attained at pH 7.5 and CT 21.5 h. The optimum conditions were composed of pH 7.67, CT 19.15 h, 10.95 and sodium acetate as carbon source, while COD, and total nitrogen removals were 94.96%, 94.93% and 93.60%, respectively. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1638–1646, 2018