Consuming the least amount of energy and resources in landfill leachate electrocoagulation

Abstract

Abstract Landfill leachate is a concoction of various toxic and difficult-to-treat compounds, rendering conventional treatment methods inadequate. In this paper, electrocoagulation (EC) was used for leachate treatment which combines the effects of sedimentation (resulting from the coagulants released by the anode) and flotation (resulting from the hydrogen bubbles coming from the cathode). The impacts of initial pH (4.0 − 8.0), electric current intensity (1.0 − 5.0 A), initial temperature (25.0 − 45 . 0 ° C), and retention time (15 − 75 min) were investigated on COD removal. Next, optimization was carried out under two scenarios. Firstly, the highest COD removal was targeted irrespective of process costs. The best performance was obtained at a pH of 5.4, current intensity of 4 A, and reaction time of 60 min with an initial temperature of 40 °C, leading to COD removal of 71.78%. However, in real-world applications, the use of energy and resources must be limited to viable levels. Hence, under the second optimization scenario, capital and operational expenditures were taken into account. The use of chemicals, electricity and heating was minimized as well as reducing the size of the equipment and tanks. With these restrictions, at a pH of 6, current intensity of 3.4 A, initial temperature of 30 °C, and process duration of 47 min, COD removal of 51% was achieved. Although in the second scenario the COD removal decreased by 20%, the energy usage was halved and the electrode consumption was reduced by more than one-third, in addition to lower capital costs for smaller equipment. Ultimately, it is up plant designers to decide which optimization criteria are the most important and what costs they are willing to accept in order to obtain higher COD removal rates. Such decisions are case-dependent (subjective) and will have to be made considering the specific conditions of each leachate treatment plant.