Composting has been recognized as an environmentally friendly way of disposing of biodegradable waste by converting it into compost. Composting process also produce the leachate that contain various hazardous substances with a negative impact on the environment. Therefore, leachate treatment is required before discharge into the natural recipient. In this paper, the amount and composition of leachate generated during the biowaste composting process in a cylindrical rotary composter (closed system) and an open container (open system) were monitored. pH, electrical conductivity, turbidity, COD and Kjeldahl nitrogen were monitored in the leachate. The results showed that leachates are characterized with high organic load, high ammonia concentration, low pH, high conductivity and turbidity, while the resulting leachate amounts showing decreasing trend. In order to treat wastewater generated during composting of biowaste, leachate was simulated from the compost mass sampled on the 21st day of composting. The simulated leachate was treated by coagulation and electrocoagulation, without and with the addition of zeolite. The efficiency of the treatment process was monitored through the parameters of pH, electrical conductivity, turbidity, COD and Kjeldahl nitrogen. Consumption of aluminum electrodes during electrocoagulation with and without the addition of zeolite was also monitored. An analysis of the operating costs of the electrocoagulation procedure (consumption of electricity, electrode material and zeolite) was performed.