Finding a suitable treatment solution for a leachate from a non-hazardous industrial solid waste landfill

Abstract The current study aimed at tackling the lack of effective treatment solutions for leachates from industrial solid waste landfills (ISWLs) through the development of a treatment train for a non-hazardous ISWL (NHISWL) leachate with low/moderate content of organics and salts and low biodegradability. The following technologies were tested: (i) coagulation using ferric chloride (FeCl3) or aluminium sulphate (Al2(SO4)3), (ii) biological oxidation, and (iii) chemical and electrochemical advanced oxidation processes (AOPs/EAOPs), including photo-Fenton oxidation using ultraviolet C (UVC) or ultraviolet A (UVA) radiation (PF-UVC or PF-UVA), anodic oxidation (AO), ozonation process and ozone (O3)-based processes. The best multistage treatment strategy included: (i) coagulation with FeCl3 for partial removal of organics (with direct impact on colour, odour and turbidity removal and biodegradability enhancement) and phosphorous, (ii) PF-UVC process for recalcitrant organics oxidation (with direct impact on colour and odour removal and biodegradability enhancement) coupled to a clarification step for removal of suspended solids, turbidity, iron and phosphorous, and (iii) biological process for removal of the generated biodegradable organics and of nitrogen compounds. Upon treatment, the NHISWL leachate fulfilled European and Portuguese requirements for discharge into aquatic systems, except for ammonium (and consequently for total nitrogen), pointing to the need to change the biological process conditions or add an air stripping step. The application of coagulation before the PF-UVC process has proved to be crucial for the fulfilment of the legislation requirements.