Conversion of sewage sludge into biochar: A potential resource in water and wastewater treatment.

Production of biochar from sewage sludge (SS) is consistent with the goal of sustainable resource recovery and promotes a wastewater-based circular economy. Thermochemical conversion of SS to biochar resolves two major issues simultaneously as it minimizes the cost of disposal and acts as a resource to eliminate the toxic contaminants from water and wastewater. The reusability and ready availability of the biochar, irrespective of the season, makes it an economically viable material for wastewater treatment. In this review, explicit insights into the production, modification and usage of SS derived biochar are provided including (i) the production yield, (ii) characteristic features such as physical, chemical, electrochemical and morphological aspects, and (iii) impact on contaminant removal through adsorption, catalytic and electrochemical processes. Particular attention is given to the use of SS derived biochar as an adsorbent for contaminants present in wastewaters, the potential use of biochar as a catalyst and support material in advanced oxidation processes and the use of biochars as an electrode material. The effect of pyrolysis conditions and co-pyrolysis with other materials on biochar properties is explored and insight is provided into the toxicity of biochar components present at different process conditions.

Occurrence of organic micropollutants in municipal landfill leachate and its effective treatment by advanced oxidation processes.

Landfilling is the most prominently adopted disposal technique for managing municipal solid waste across the globe. However, the main drawback associated with this method is the generation of leachate from the landfill site. Leachate, a highly concentrated liquid consisting of both organic and inorganic components arises environmental issues as it contaminates the nearby aquifers. Landfill leachate treatment by conventional methods is not preferred as the treatment methods are not much effective to remove these pollutants. Advanced oxidation processes (AOPs) based on both hydroxyl and sulfate radicals could be a promising method to remove the micropollutants completely or convert them to non-toxic compounds. The current review focuses on the occurrence of micropollutants in landfill leachate, their detection methods and removal from landfill leachate using AOPs. Pharmaceuticals and personal care products occur in the range of 10-1 to more than 100 µg L-1 whereas phthalates were found below the detectable limit to 384 µg L-1, pesticides in the order of 10-1 µg L-1 and polyaromatic hydrocarbons occur in concentration from 10-2 to 114.7 µg L-1. Solid-phase extraction is the most preferred method for extracting micropollutants from leachate and liquid chromatography (LC) - mass spectrophotometer (MS) for detecting the micropollutants. Limited studies have been focused on AOPs as a potential method for the degradation of micropollutants in landfill leachate. The potential of Fenton based techniques, electrochemical AOPs and ozonation are investigated for the removal of micropollutants from leachate whereas the applicability of photocatalysis for the removal of a wide variety of micropollutants from leachate needs in-depth studies.

Treatment of dairy industry wastewater by combined aerated electrocoagulation and phytoremediation process.

As dairy industries has been emerged as one of the most rapidly developing industry in both small as well as large scale, the volume of effluent generated is also very high. In the present study, aerated electrocoagulation combined with phytoremediation treatment was conducted in dairy industry wastewater. Electrocoagulation was performed with aluminium and iron electrodes and effect of various operating parameters such as electrode combination, pH, and voltage were tested. Electrocoagulation was found effective at neutral pH and its efficiency increased with increase in applied voltage. The maximum COD removal efficiency of 86.4% was obtained in case of Al-Fe electrode combination with aeration at 120 min reaction time, initial pH 7, voltage 5 V. Significant growth of Canna indica was observed in electrocoagulation treated wastewater compared to raw dairy wastewater. COD removal of 97% was achieved when combined electrocoagulation and phytoremediation process was used. Thus, it proves to be a proficient method for the treatment of dairy industry wastewater. In addition to the above, bacterial toxicity tests were performed to investigate the toxic nature of wastewater and the results showed that both treated and untreated wastewater favoured bacterial growth.

Photocatalytic Degradation of a Chlorinated Organic Chemical Using Activated Carbon Fiber Coupled with Semiconductor.

Hydrothermal mediated synthesis was used to couple activated carbon fiber and semiconductor. Batch mode photocatalytic experiments were performed to investigate the efficacy of the developed photocatalyst in the degradation of 2, 4-dichlorophenol. Operational parameters including initial concentration of 2, 4-dichlorophenol and catalyst loading were optimized at natural pH conditions. Addition of inorganic anions during the degradation revealed that the presence of anions greatly affects the degradation efficiency. The significance of highly reactive radicals on the photocatalytic degradation was identified by the addition of radical scavengers such as isopropanol (OH˙), benzoquinone (˙ O 2 - ) and potassium iodide (h+ ). Reusability of the photocatalyst was confirmed by conducting five cyclic studies. Further, the dissolution of Zn2+ in the solution was analyzed and determined to be 0.199 µg mL-1 . Seed germination study was conducted to examine the toxicity nature of ZnO on growth and development of Vigna radiata.