INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH W. Sudjarid and P.Jarupunphol., Vol.9, No.2, June, 2019 Characeae and Hydrilla verticillata for Enhancing Biogas Production in Landfill Leachate Wichidtra Sudjarid* ‡ , Pita Jarupunphol** *Department of Environmental Science, Faculty of Science and Technology, Sakon Nakhon Rajabhat University, 47000 ** Department of Information Technology, Faculty of Science and Technology, Phuket Rajabhat University, 83000 (Wichidtra.s@snru.ac.th, p.jarupunphol@pkru.ac.th) ‡ Wichidtra Sudjarid; Pita Jarupunphol, 47000, Tel: +66 84 128 4421, Fax: +66 042 970 029,wichidtra.s@snru.ac.th Received: 14.04.2019 Accepted:13.05.2019 Abstract- This study investigated the enhancement of biogas production in leachate wastewater under anaerobic digestion process. Characeae and Hydrilla verticillata were collected from a natural water resource, then shredded at a ratio of 1:1 (w/v) and used as a co-substrate. The simulated reactors were stabilised within 60 days of incubation. Five ratios of leachate to co-substrate as 10:1, 10:2, 10:3, 10:4 and 10:5 were separately tested. It found that the pH ranged from 5.83 to 7.78 and 5.63 to 7.35 in Hydrilla and Characeae, respectively. The COD degradation efficiency was a range of 65 – 81% and 55 – 68% in Hydrilla and Characeae, but leachate seems to be retarded. The accumulative biogas production in leachate was significantly improved, while the biogas production in leachate was 2.6 mL. The highest accumulative biogas production was found 5193, 2943, 5654 and 5843 mL in sole and ratio five in Hydrilla, 100% and ratio four in Characeae. Moreover, these substrates could generate densely and sustained of H2 and could initiate CH4 after 20 days. This suggests an advantage of using Characeae and Hydrilla verticillata as a co-substrate to improve biogas and CH4 production in long operating landfill leachate. Keywords Characeae, Hydrilla verticillata, Leachate, Biogas, Anaerobic Digestion. 1. Introduction Leachate wastewater management is one of the most challenging issues for developing countries. It is a consequence of the compost of organic solid waste from the landfill. The municipal solid waste has been reported to be approximately 27 Mt across Thailand [1]. Sanitary landfill with the dumping of 1,000 t/d could produce about 200-300 t/d of leachate and more or less depending on its climate location and moisture content [2]. There are several factors affecting the quality of leachate (i.e. age, type, and composition of waste) [3]. Notably, leachate characteristics were mainly dependent upon the age of landfill [4]. The old leachate (> 10 years) was recalcitrant to biodegradation due to the long residue of organic molecules released from the solid waste [5]. The old landfill is, however, characterised by its low biodegradable and relatively high NH3-N, which could be inhibitory to microbial activity [3, 6]. However, high content of N could stabilizes the pH and the isobutyric and valeric acids that increase the biogas production [7]. A lesser measurement and low headspace pressure represented positive effect in biogas production [8]. Nevertheless, anaerobic digestion has the potential to degrade organic contents and convert them to biogas in leachate as renewable energy [9]. Co-digestion is a mix of at least two different wastes digested. Significant benefits of applying the co-digestion have been observed, e.g., improving the degradation process stability, increasing in biogas and methane yield, and utilising of a synergistic effect of microorganisms [10]. Please note that applications of fruit and vegetable waste [11], co-digestion of different mixtures of seaweed, food waste leachate, vegetation, algal biomass, and raw sludge could cause methane production more than using only individual substrates [12, 13, 14]. The mixed silage of waterweed biomass and wheat straw in a long-term semi-continuous could produce biogas effectively [15]. The eutrophic lake contains nutrients dissolved in water lake that