Minimization of hazardous sludge production using a bioelectrochemical system supplied by an alternating current electric field

Environmental pollution removal using electrostimulation of microorganisms by alternative current

The entrance of some toxic and hazardous chemical agents such as antibiotics, pesticides, and herbicides into the environment can cause various problems to human health and the environment. In recent years, researchers have considered the use of electrostimulation in the processes of microbial metabolism and biological systems for the treatment of pollutants in the environment. Although several electrostimulation reports have been presented for pollutant removal, little attention has been paid to alternative current (AC) biostimulation. This study presents a systematic review of microbial electrostimulation using bioelectrochemical systems supplied with AC. The utilization of alternating current bioelectrochemical systems (ACBESs) has some advantages such as the provide of appropriate active biofilms in the electrodes due to the cyclical nature of the current and energy transfer in an appropriate manner on the electrode surfaces. Moreover, the ACBESs can reduce hydraulic time (HRT) under optimal conditions and reduce the cost of converting electricity using AC. In microbial electrostimulation, amplitude (AMPL), waveform, C/N, and current have a significant effect on increasing the removal efficiency of the pollutants. The obtained results of the meta-analysis illustrated that various pollutants such as phenol, antibiotics, and nitrate have been removed in an acceptable range of 96% using the ACBESs. Therefore, microbial electrostimulation using AC is a promising technology for the decomposition and removal of various pollutants. Moreover, the ACBESs could provide new opportunities for promoting various bioelectrochemical systems (BESs) for the production of hydrogen or methane.

Optimizing the hydrolysis-acidification stage in municipal wastewater treatment: comparison of immobilized fillers and granular sludge

The decomposition of organic macromolecules in sewage currently benefits substantially from hydrolysis-acidification. The full use of its qualities can help domestic sewage to biodegrade more quickly, which promotes the subsequent aerobic reactions. This study evaluated the hydrolysis-acidification performance of granular sludge and filler in residential sewage. Both forms were highly effective at producing volatile fatty acids (VFAs) at the beginning of the reaction, but the granular sludge gradually disintegrated over time, particularly at low temperatures. The production of VFAs decreased (68.08 mg/L), and the effluent dissolved organic nitrogen (DON) increased (6.23 mg/L). However, the effluent of fillers remained at a lower level (1.3 mg/L) and produced more VFAs (74.13 mg/L). High-throughput sequencing revealed that the filler included a greater quantity of hydrolytic-acidifying bacteria than the granular sludge, which resulted in higher performance. In this study, the optimal form of utilizing hydrolytic acidifying bacteria was discussed to provide a theoretical basis to improve the full utilization of organic matter in domestic sewage and the removal of as much total nitrogen as possible.

Mechanism and application of modified bioelectrochemical system anodes made of carbon nanomaterial for the removal of heavy metals from soil

Bioelectrochemical techniques are quick, efficient, and sustainable alternatives for treating heavy metal soils. The use of carbon nanomaterials in combination with electroactive microorganisms can create a conductive network that mediates long-distance electron transfer in an electrode system, thereby resolving the issue of low electron transfer efficiency in soil remediation. As a multifunctional soil heavy metal remediation technology, its application in organic remediation has matured, and numerous studies have demonstrated its potential for soil heavy metal remediation. This is a ground-breaking method for remediating soils polluted with high concentrations of heavy metals using soil microbial electrochemistry. This review summarizes the use of bioelectrochemical systems with modified anode materials for the remediation of soils with high heavy metal concentrations by discussing the mass-transfer mechanism of electrochemically active microorganisms in bioelectrochemical systems, focusing on the suitability of carbon nanomaterials and acidophilic bacteria. Finally, we discuss the emerging limitations of bioelectrochemical systems, and future research efforts to improve their performance and facilitate practical applications. The mass-transfer mechanism of electrochemically active microorganisms in bioelectrochemical systems emphasizes the suitability of carbon nanomaterials and acidophilic bacteria for remediating soils polluted with high concentrations of heavy metals. We conclude by discussing present and future research initiatives for bioelectrochemical systems to enhance their performance and facilitate practical applications. As a result, this study can close any gaps in the development of bioelectrochemical systems and guide their practical application in remediating heavy-metal-contaminated soils.

Role of bio-electrochemical technology for enzyme activity stimulation in high-consumption pharmaceuticals biodegradation

Active pharmaceutical ingredients (APIs) and their intermediate residues have recently been considered a serious concern. Among technologies, bio-electrochemical technologies (BETs) have stimulated the production of bio-electrical energy. This review aims to examine the benefit and mechanism of BETs on the degradation of high-consumption pharmaceutical compounds, including antibiotic, anti-inflammatory, and analgesic drugs, and the stimulation of enzymes induced in a bioreactor. Moreover, intermediates and the proposed pathways of pharmaceutical compound biodegradation in BETs are to be explained in this review. According to studies performed exclusively, the benefit of BETs is using bio-electroactive microbes to mineralize recalcitrant pharmaceutical contaminants by promoting enzyme activity and energy. Since BETs use the electron transfer chain between bio-anode/-cathode and pharmaceuticals, the enzyme activity is essential in the oxidation and reduction of phenolic rings of drugs and the ineffective detoxification of effluent from the treatment plant. This study is suggested a vital and influential role of BETs in mineralizing and enzyme induction in bioreactors. Eventually, a content of future developments or outlooks of BETs are propounded to improve the pharmaceutical industries' wastewater problems.

Bio-electrical stimulation process on degradation of Phenanthrene from aqueous solution using a novel anode modified with carbon cloth: Operational performance, microbial activity and energy

Phenanthrene as the hazardous PAHs-component are extensively detected in industrial wastewater. However, the impacts of bioelectrostimulation process on Phenanthrene degradation in aerobic reactors remained unclear. Here, a novel bioelectrostimulation process equipped with carbon cloth as electrodes was developed to investigate the removal efficiency of Phenanthrene and ATPase enzyme activity in the synthetic wastewater. The results obtained from the present study indicated that a complete Phenanthrene degradation (100%) can be achieved using microbial electrostimulation systems steel mesh coated with carbon cloth (MES-CC) as anode under optimal operational conditions (electrical current: 4 mA, HA concentration: 15 mg L^-1) within 18 h. The conductive carbon cloth provides a biofilm carrier to easily transfer the electrons between electrodes and microbial communities. In addition, the highest ATPase enzyme activity (5176 U) was observed when the aerobic MES-CC reactors were operated with electrical current 4 mA. Furthermore, the COD removal efficiency in MES-CC increased from 49% to 96% when the C: N ratio decreased from 20 to 5. The highest value of V_max in MES-CC for suspended and attached growth were determined to be 2.87 and 0.54 g COD g^-1 biomass. Overall, the results demonstrated that MES equipped with carbon cloth and continuous electrical current mode has good potential for efficient Phenanthrene wastewater treatment.

Investigation on the improved electrochemical and bio-electrochemical treatment processes of soilless cultivation drainage (SCD)

The soilless crop cultivation under cover generates wastewater called soilless cultivation drainage (SCD), being a nutrient-rich overflow. The average concentration of phosphorus- and nitrogen-based pollutants from soilless tomato cultivation usually ranges from 35.4 to 104.0 mg P/L and from 270.0 to 614.9 mg N/L, respectively. In bio-electrochemical reactors, nitrogen and phosphorus are removed via biological denitrification, electrochemical nitrate reduction, bio-electrochemical reduction, and electrocoagulation. The novelty of this study is due to the use of alternating current (AC), which can both mitigate the corrosion on the anode and solve the issue of insoluble oxide build-up on the cathode. Additionally, and crucially, it promotes bacterial growth and activity. The aim of the present study was to determine (1) the effectiveness of soilless cultivation drainage treatment methods that employ biological and electrochemical processes, with consideration given to (2) the quantity and quality of the produced sludge as a potential nutrient-rich product. The bio-electrochemical reactor proved more effective than the electrochemical one and ensured a high TP and TN removal efficiency exceeding 97% and 66%, respectively. The resulting sludge was rich in such elements as calcium, potassium, carbon, phosphorus, and nitrogen, and as such may serve as a viable alternative to conventional mineral fertilizers.