Effect on heavy metals concentration from vermiconversion of agro-waste mixed with landfill leachate Azizi Abu Bakar a,b,⇑ , Choy May Yee a , Noor Zalina Mahmood a,b , Noorlidah Abdullah a,b a Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia b Mushroom Research Centre, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 24 June 2014 Accepted 17 January 2015 Available online 7 February 2015 Keywords: Heavy metal mass balance Livestock excreta Lumbricus rubellus Pleurotus sajor-caju Vermicompost abstract Spent Pleurotus sajor-caju compost mixed with livestock excreta, i.e. cow dung or goat manure, was contaminated with landfill leachate and vermiremediated in 75 days. Results showed an extreme decrease of heavy metals, i.e. Cd, Cr and Pb up to 99.81% removal as effect of vermiconversion process employing epigeic earthworms i.e. Lumbricus rubellus. In addition, there were increments of Cu and Zn from 15.01% to 85.63%, which was expected as non-accumulative in L. rubellus and secreted out as contained in vermicompost. This phenomenon is due to dual effects of heavy metal excretion period and mineralisation. Nonetheless, the increments were 50-fold below the limit set by EU and USA compost limits and the Malaysian Recommended Site Screening Levels for Contaminated Land (SSLs). Moreover, the vermicompost C:N ratio range is 20.65–22.93 and it can be an advantageous tool to revitalise insalubrious soil by acting as soil stabiliser or conditioner. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Malaysia’s high annual rainfall due to the tropical climate cou- pled with high moisture contents from the incoming waste stream have led to the significant impact of leachate generation from landfills. As reported by Kortegast et al. (2007), the resulting base flow of leachate in the Bukit Tagar landfill (15–20% of the mass of incoming waste) is significantly higher than that experienced even in Hong Kong (5–10% of the waste mass) and is a major contributor to the total flow (approximately 60% annually at Bukit Tagar). In addition, Kortegast et al. (2007) also provided calibrated estimates of infiltration for intermediate cover slopes and con- firmed the critical nature of rigorous water exclusion measures in such a wet climate as auxiliary evidence to the total flow of leachate in the Bukit Tagar landfill. Leachate treatment plants in the landfill treat up to 1000 cubic metres of leachate per day and irrigate a 120-acre field (instead of discharging into open-water courses) following the biological treatments (Sequential Batch Reactors (SBRs), Dissolved Air Floatation (DAF) plant and Reed Beds Polishing by using Phragmites plant). However, the treatments do not specify uptake for certain non-degraded pollutants, namely heavy metals, which potentially migrate into soil and further bioaccumulate in the ecosystem food chain. Heavy metal removal from aqueous solutions and soil has been the focus of research in recent years. The removal of heavy metals is achieved through var- ious techniques, such as electrokinetic treatment, chemical oxida- tion or reduction, leaching, solidification, vitrification, excavation and off-site treatment (Aboulroos et al., 2006). In the aqueous solution treatments, the adsorbents used were difficult to separate from the wastewater, while the soil treatments were highly priced relative to the large hectare areas. Proper and profitable management via recycling of agricultural waste generated, including livestock excreta, into a valuable product such as compost is an environmentally sound practice. Integrating leachate with an enormous amount of organic waste for earthworm feed materials in vermiconversion could be an effective technique in the bioremediation of contaminated landfill leachate. Vermiconversion is an efficient eco-biotechnology tool utilising earthworms to decompose organic waste into a valuable product, henceforth called vermicompost, as a final product. This eco-biotechnology tool involves the aerobic, bioxidation and stabi- lisation of non-thermophilic processes of organic waste facilitated by earthworms to fragment, mix and promote microbial activity. Technically, the vermiconversion process involves physical/ mechanical (mixing and grinding) and biochemical activities (microbial decomposition in the earthworms’ intestine) (Loh et al., 2005). The effect of heavy metals concentration in vermicon- version utilising Lumbricus rubellus has been tested in previous http://dx.doi.org/10.1016/j.wasman.2015.01.020 0956-053X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. Tel.: +60 3 79674635/ 79674353; fax: +60 3 79677813/79674178. E-mail addresses: azieaxis@gmail.com, azizi.bkr@um.edu.my (A.B. Azizi). Waste Management 38 (2015) 431–435 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman