Anaerobic co-digestion of Batik wastewater with macroalgae

Macroalgae is one of renewable marine biomass feedstocks for substituting land biomass. With the use of anaerobic digestion (AD) technology, macroalgae has been greatly acknowledged for bioenergy production resources, including biogas. On the other hand, Batik wastewater contains chemical dyes and organic pollutants, which potentially cause environmental pollution if disposed without a proper treatment. The aims of this research were to evaluate the potential of biogas and methane production using different ratio of Batik wastewater: macroalgae (i.e. Gracilaria verrucosa fresh and dried samples) and to estimate the electrical potential generated. A biochemical methane potential (BMP) test was carried out at temperature of 37 °C for 28 days under batch condition. The results indicated that digesting Batik wastewater alone, without dilution, showed an inhibition process as indicated by a negative net biogas and methane production as well as the specific methane production (SMP). Co-digesting Batik wastewater with fresh marine G. verrucosa samples at ratio of 50:50 cannot produce a high amount of biogas or methane. All samples showed a similar biogas or methane volume compared to that of the inoculum sample. This indicated that an inhibition was occurred limiting the microbial consortia in inoculum to breakdown the organic matter in the feedstock material. This could be due to the salinity of macroalgae and the high organic pollutant concentration in Batik wastewater. However, co-digestion of Batik wastewater with dried marine G. verrucosa produced higher SMP. Further alternative options to enhance to utilisation of Batik wastewater are needed.