In situ coagulation-electrochemical oxidation of leachate concentrate:A key role of cathodes

To efficiently remove organic and inorganic pollutants from leachate concentrate,an in situ coagulation-electrochemical oxidation(CO-EO)system was proposed using Ti/Ti_(4)O_(7)anode and Al cathode,coupling the“super-Faradaic”dissolution of Al.The system was evaluated in terms of the removal efficiencies of organics,nutrients,and metals,and the underlying cathodic mechanisms were investigated compared with the Ti/RuO_(2)-IrO_(2)and graphite cathode systems.After a 3-h treatment,the Al-cathode system removed 89.0%of COD and 36.3%of total nitrogen(TN).The TN removal was primarily ascribed to the oxidation of both ammonia and organic-N to N_(2).In comparison,the Al-cathode system achieved 3-10-fold total phosphorus(TP)(62.6%)and metal removals(>80%)than Ti/RuO_(2)-IrO_(2)and graphite systems.The increased removals of TP and metals were ascribed to the in situ coagulation of Al(OH)_(3),hydroxide precipitation,and electrodeposition.With the reduced scaling on the Al cathode surface,the formation of Al^(3+)and electrified Al(OH)_(3)lessened the requirement for cathode cleaning and increased the bulk conductivity,resulting in increased instantaneous current production(38.9%)and operating cost efficiencies(48.3 kWh kg_(COD)^(−1)).The present study indicated that the in situ CO-EO process could be potentially used for treating persistent wastewater containing high levels of organic and inorganic ions.

A “Seawater-in-Sludge” approach for capacitive biochar production via the alkaline and alkaline earth metals activation

Sewage sludge is a potential precursor for biochar production,but its effective utilization involves costly activation steps.To modify biochar properties while ensuring cost-effectiveness,we examined the feasibility of using seawater as an agent to activate biochar produced from sewage sludge.In our proof-of-concept study,seawater was proven to be an effective activation agent for biochar production,achieving a surface area of 480.3 m^(2)/g with hierarchical porosity distribution.Benefited from our design,the catalytic effect of seawater increased not only the surface area but also the graphitization degree of biochar when comparing the pyrolysis of sewage sludge without seawater.This leads to seawater activated biochar electrodes with lower resistance,higher capacitance of 113.9 F/g comparing with control groups without seawater.Leveraging the global increase in the salinity of groundwater,especially in coastal areas,these findings provide an opportunity for recovering a valuable carbon resource from sludge.

Enzymatic nitrous oxide emissions from wastewater treatment

Nitrous oxide （N20）, a potent greenhouse gas, is emitted during nitrogen rernoval in wastewater treatment, significantly contributing to greenhouse effect. Nitrogen removal generally involves nitrification and denitrification catalyzed by specific enzymes. N20 production and consumption vary considerably in response to specific enzyme-catalyzed nitrogen imbalances, but the mechanisms are not yet completely understood. Studying the regulation of related enzymes＂ activity is essential to minimize N20 emissions during wastewater treatment. This paper aims to review the poorly understood related enzymes that most commonly involved in producing and consuming N20 in terms of their nature, structure and catalytic mechanisms. The pathways of N20 emission during wastewater treatment are briefly introduced. The key environmental factors influencing N20 emission through regulatory enzymes are summarized and the enzyme-based mechanisms are revealed. Several enzyme- based techniques for mitigating N20 emissions directly or indirectly are proposed. Finally, areas for further research on N20 release during wastewater treatment are discussed.