Experimental evaluation of anaerobic digestion for coffee wastewater treatment and its biomethane recovery potential

Abstract

The objective of this study was to evaluate the performance of anaerobic digestion (AD) as an ecofriendly technology for coffee wastewater (CWW) management. First, we have characterized the CWW and found that it is suitable for microbial degradation with pH adjustment. Then, we designed a simple anaerobic batch reactor (ABR) and evaluated its potential for energy yield and efficiency to remove pollutants. The experiment was carried out by operating the anaerobic digestion (AD) for 70 days. The ABR was found to be efficient for the removal of organic load (90 %), nutrients (82 %) and suspended solids (95 %) from coffee processing waste. The increased removal efficiency of pollutants was dependent on the hydraulic retention time of the system. We also estimated that the coffee waste has a potential to produce a theoretical energy yield of 4-10 million KJ/day and an organic fertilizer (digestate) of 18.8-25.2 kg VSS/day. As a result, the AD would be a more sensible consideration as an eco-friendly treatment option for the coffee waste. The use of AD for CWW treatment not only reduces emission of greenhouse gases to the environment but also circumvents the rising demand for fuel wood and charcoal that causes a severe deforestation in the coffee growing regions of the world.

Environmental Flows Risk Assessment of Effluent Outfalls from Conventional Wet Washed Coffee Refineries in Limu Kosa District of Southwestern Ethiopia

“…There were highly significant inconsistencies of interaction effect of BOD and COD among all river waters at (p<0. 05 2 and Bonke ENP as well as EFF and PUS of all river water at (p≤ 0.05 and 0.01). This is due to highly mobility or fixation of TN concentration among each river water sites.…”

“…Mean separation of difference in concentration levels obtained for a given parameter along Eflows & sampling sites were considered as significant if calculated P-values were < 0.05. To evaluate its capacity of coffee wastewater (organic load) and nutrients treatment performance of the conventional lagoon pond (traditionally waste stabilization ponds) were calculated using following formula of [2].…”

“…This deterioration of the ecohydrological integrity of freshwater systems river basin quality increases as soon as during the peak time of CWCR time alarmingly increasing rampant discharges into the river basin. The river water bodies located nearby were disrupted by most processing, because CWCR use large quantities of water for fermentation, receiving the cherries, transporting them hydraulically through the pulping machine, removing the pulp, and sorting and re-passing any cherries with residual pulp adhering to them as done by [2][3].…”

“…This result revealed that conventional lagoon pond (traditionally waste stabilization ponds) is not an eco-friendly waste management option to treat the coffee wastewater effectively. Also the conventional wastewater treatment systems (lagoons) that were intended to serve as assimilation capacity and removal of effluent outfalls from CWCR were properly did not construct nor were they of the right dimension to accommodate the generated effluent during peak time of refineries [2]. Although this fact is widely recognized, lead to overflow of effluents into river water body nearby is a common occurrence.…”

“…These are modern or advanced and conventional wet washed coffee refineries (CWCR). The modern or advanced are subjected to mechanical removal of the parchment layer from the bean and the CWCR are biological (anaerobic) which is simply dumping it into the river bank [1][2].…”