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Report, 1996

The modelling of an anaerobic digestion plant and a sewage plant in the ORWARE simulation model

Dalemo, Magnus


A simulation model, called ORWARE (ORganic WAste REsearch model), has been developed for evaluation of handling alternatives for organic waste. The model deals with both source separated solid organic waste and liquid organic waste i.e. wastewater. Included are transport for collection, incineration, landfilling, anaerobic digestion, composting, transportation of residuals and spreading on arable land. The model is intended for simulation of handling scenarios for organic waste and calculates emissions to air, water, recirculation to arable land and energy turnover. The flows in the model are described by a variable vector of 43 substances, including e. g. plant nutrients, heavy metals and some organic priority pollutants. The construction of the models for anaerobic digestion, sewage plant, sewage system and spreading of residuals included in ORWARE, are described in detail. The anaerobic digestion model is a continuous, single stage, mixed tank reactor (C.S.T.R.) operating under mesophilic conditions. The gas production is related to the retention time and the maximum degradation ratio and first order rate constant, for the organic components fat, protein and three classes of carbohydrates respectively. The combustion of the gas in a stationery engine is also included. The sewage plant model includes mechanical, biological and chemical treatment of the wastewater, and anaerobic digestion and dewatering of the sewage sludge. The separation of sludge is based on the suspended solids and water separated in the respectively treatment processes with data primarily from the plant in Uppsala. Separation of the remaining substances included in the vector is principally modelled from assumptions of the substances to be attached to the suspended solids or soluble in water. Sewage systems included are conventional systems and vacuum systems. The model deals with leakage and energy consumption. Alternatives in ORWARE are also urine separation and kitchen disposers for transporting and treating the solid organic waste in a sewage plant. These alternatives changes the substrate composition and water quantity sent to the sewage plant. The model for spreading of residuals includes three types of spreaders, depending on the residues water content. It models energy consumption and emissions from the tractor.



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Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet

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