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Anaerobic co-digestion of fruit juice and municipal bio-waste in the Okanagan Valley

University of British Columbia

Fruit harvesting and juice making is one of the most important sectors in the Okanagan Valley. Fruit- juice production generates industrial wastewater with high organic strength that needs to be treated, generally on-site, prior to being discharged to the municipal wastewater treatment system. In the Okanagan Valley, the organic residuals of fruit-juice wastewater treatment, such as screen cake and thickened waste activated sludge, are currently being sent to local landfills or composting facilities, which is not desirable. Given the growing interest in utilizing industrial, agricultural and municipal waste streams in centralized bioreactors for optimized energy (biogas) recovery, this study evaluated the anaerobic co-digestion performance of industrial organic streams from Sun-Rype Products Ltd. wastewater treatment facility with municipal waste sludge cake from Kelowna’s municipal wastewater treatment plant. Excess landfill leachate source at the Glenmore Landfill was also utilized to dilute some of the concentrated streams and provided additional buffering capacity. Both single and co-digestion scenarios were tested in laboratory-scale mesophilic and thermophilic semi-continuous flow digesters at sludge retention times of 20 and 10 days, corresponding to organic digester loading rates of 1.41-4.80 g chemical oxygen demand /L/day. Digestion studies demonstrated that co-digestion of fruit-juice streams with municipal sludge cake and leachate resulted in more stable operation even at the higher loading due to additional buffering capacity available compare to single scenarios. In addition, organic removal efficiencies were higher for the co-digestion scenarios. Furthermore, dewaterability of municipal sludge cake was enhanced by the addition of industrial secondary sludge. Thermophilic digestates could qualify under Class A biosolids according to Organic Matter Recycling Regulation (OMRR) of BC in terms of coliform presence; however presence of higher coliforms at mesophilic digestion temperatires downgraded the mesophilic digestates to Class B biosolids. Finally, ppreliminary cost analysis indicated an overall saving of $10.52 million ($2 million in capital and $8.52 million in operational) over 25-year period for a co-digestion scenario utilizing all waste streams over building/operating two separate digesters for municipal and industrial waste streams.

Text

2014-10-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/44523

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/