High presence of seaweed in marine environments and coastal areas can cause serious hygienic and environmental problems. Anaerobic digestion could provide a solution being beneficial at producing bioenergy and fertilizer. However, AD of algae biomass has some limitations and consolidation of the process is required. To so increase the process efficiency, batches of 350 mL of feedstocks contained seaweed biomass (Sargassum sp.), inoculum and different dosages of sludge from drinking water treatment (DWTS as a micronutrient source to improve biogas production) were digested in 500 mL glass reactor and at mesophilic conditions, leading to significantly enhanced methane production. The highest methane yield (199 Nml g-1 VS) was observed when 6 mg L-1 DWTS was added, which showed a 30% improvement compared to control digester and accounted for 249.4 kWh increase in net energy per ton. Furthermore, the biodegradability index following DWTS addition also increased by 10% compared with the control.

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