Co-digestion of organic rich wastes and wastewater sludge to enhance biogas production has become an attractive economic possibility for water utilities. The suitability of the organic rich waste depends on its ability to produce biogas as well as its influence on the overall anaerobic digestion process. Biomethane potential evaluation was conducted to screen seven organic wastes and dehydrated algae. All co-substrates increased the bio-methane yield by three to six times compared with conventional anaerobic digestion of sewage sludge. Maximum co-digestion ratios were identifiable for most solid co-substrates including algae (6% wt/wt), undiluted food waste (5% wt/wt), bakery waste (5% wt/wt), and diluted commercial food waste (10% wt/wt). On the other hand, the maximum co-digestions ratio of beverage reject and sewage sludge was 10% (wt/wt). With the exception of fat-oil-grease, all solids free liquid co-substrates evaluated in this study showed a notable synergistic effect, to enhanced removals of total solids, volatile solids (VS) and chemical oxygen demand (COD) during anaerobic digestion. The increase in COD removal when co-digesting wastewater sludge and liquid waste was from 2 to 41%. Conversely, the co-digestion of most solid cosubstrates resulted in additional VS and COD residuals in the final biosolids. Elevated concentrations of sulphur and phosphorous in all food waste co-substrates suggest that control measures to address H2S in biogas and the accumulation of phosphorus in sludge centrate may be necessary during full scale operation. Data presented here provide the basis for subsequent pilot scale evaluation of anaerobic digestion of these organic rich wastes and wastewater sludge. Co-digestion of organic rich wastes and wastewater sludge to enhance biogas production has 12 become an attractive economic possibility for water utilities. The suitability of the organic 13 rich waste depends on its ability to produce biogas as well as its influence on the overall 14 anaerobic digestion process. Biomethane potential evaluation was conducted to screen seven 15 organic wastes and dehydrated algae. All co-substrates increased the bio-methane yield by 16 three to six times compared with conventional anaerobic digestion of sewage sludge. 17Maximum co-digestion ratios were identifiable for most solid co-substrates including algae 18 (6% wt/wt), undiluted food waste (5% wt/wt), bakery waste (5% wt/wt), and diluted 19 commercial food waste (10% wt/wt). On the other hand, the maximum co-digestions ratio of 20 beverage reject and sewage sludge was 10% (wt/wt). With the exception of fat-oil-grease, all 21 liquid co-substrates evaluated in this study showed a notable synergistic effect, to enhanced 22 removals of total solids, volatile solids (VS) and chemical oxygen demand (COD) during 23 anaerobic digestion. The increase in COD removal when co-digesting wastewater sludge and 24 liquid waste was from 2 to 41%. Conversely, the co-digestion of most solid co-substrates 25 resulted in additional VS and COD resi...

Effects of operational disturbance and subsequent recovery process on microbial community during a pilot-scale anaerobic co-digestion

Soft drink beverage waste (BW) was evaluated as a potential substrate for anaerobic co-digestion with sewage sludge to increase biogas production. Results from this study show that the increase in biogas production is proportional to the increase in organic loading rate (OLR) rate due to BW addition. The OLR increase of 86 and 171% corresponding to 10 and 20% BW by volume in the feed resulted in 89 and 191% increase in biogas production, respectively. Under a stable condition, anaerobic co-digestion with BW did not lead to any significant impact on digestate quality (in terms of COD removal and biosolids odour) and biogas composition. The results suggest that existing nutrients in sewage sludge can support an increase in OLR by about 2 kg COD/m/d from a carbon rich substrate such as soft drink BW without inhibition or excessive impact on subsequent handling of the digestate.

Anaerobic co-digestion (AcoD) has the potential to utilise spare digestion capacity at existing wastewater treatment plants to simultaneously enhance biogas production by digesting organic rich industrial waste and achieve sustainable organic waste management.

This study examines the changes in microbial community diversity and structure in response to anaerobic co-digestion (AcoD) between sewage sludge and a carbon-rich organic waste.