Hydroxyl radical (OH) scavenging in young and mature landfill leachates

Soft drink wastewater treatment by electrocoagulation–electrooxidation processes

“…Organic matter is attributed to sugars, artificial colors and flavors used in soft drink industry, the BOD5/DQO ratio of 0.019, shows a very low biodegradability and the relation between COD/TOC, shows that COD is 2.2 times higher than TOC, it means that less than half of pollutants are organic matter, the rest are inorganic ions in the solution such as sulfates, phosphates and specially the alkalinity, all of which inhibits the oxidation of organic matter and give good stability to the wastewater. Previous research has reported that the rate constants for the oxidation of dissolved substances are inhibited by organic and inorganic scavengers [40]. The presence of nutrients like total nitrogen and total phosphorous are slightly elevated (50.7 and 18.7 mg L -1 ), according to Mexican regulations for total nitrogen and phosphorous, the maximum allowable limits are 40 and 20 mg L -1 , monthly average, respectively, which could cause the eutrophication of aquatic systems.…”

“…This behavior can be explained according equilibrium diagram, where Cu 2+ is present at acid pH (1-4), while at basic pH (8-13) the species corresponds to Cu(OH)2 formation, this agrees with the green sludge observed during the EC process. However only 37.67% of COD and 27% of TOC were removed at pH 8, this poor efficiency could be associated to the high concentration of inorganic ions in the solution such as sulfates, phosphates and alkalinity, all of which inhibits the oxidation of organic matter [40].…”

“…The organic load was significantly decreased, but the ions in solution (sulfates, alkalinity, and chlorides), inhibit the rate of oxidation of organic matter [40]. It is important to note that the nitrogenous matter was reduced by 84% as total nitrogen, which is oxidized to nitrate and subsequently reduced to nitrogen gas, and this can be proved with the concentration of nitrates in raw wastewater, which contains 0.96 mg L -1 , after the EC process, this parameter is increased to 2.7 mg L -1 and finally in the process of EO decreases to 1.8 mg L -1 , however 10 mg L -1 of nitrate is the allowable limit according to Mexican standards.…”

Advanced Oxidation Processes: Process Mechanisms, Affecting Parameters and Landfill Leachate Treatment

“…DOM consists of large macromolecular organic compounds such as humic and fulvic substances. Ghazi et al (2014) stated that DOM can react with O 3 to produce ÁOH; however, high concentration of DOM will scavenge the ÁOH produced in AOPs. Beltran (2004) also pointed out DOM can promote or inhibit the O 3 decomposition process depending on the nature of DOM; the proposed mechanism in the presence of DOM is shown by eq 48 (Acero and Gunten, 2000;Westerhoff, 1999).…”

“…However, researchers often criticized AOPs because of its high treatment cost (Matošic et al, 2008;Chamarro et al, 2001) regardless of its excellent treatment efficiency. Due to the above-mentioned reason, AOPs are not favoured as a standalone system for complete mineralization of organic compounds (Ghazi et al, 2014). Therefore, the focus of AOPs in landfill leachate treatment is to degrade recalcitrant compounds and improve biodegradability of landfill leachate.…”