Jolanta Sobik-Szołtysek, Iwona Kupich
Czestochowa University of Technology, Poland
corresponding author’s e-mail:
Abstract
EU directives on the landfill of waste oblige member states to gradually reduce the deposit of biodegradable waste in landfills. In particular, the entire mass of green waste should be transformed into compost, representing a valua-ble material. Scientific publications contain numerous reports concerning co-composting of green waste with other types of waste materials, including mineral ones. Appropriate choice of input materials may have a positive effect on the prop-erties of the final product. In particular, improving the sorption capacity of compost in terms of the possibility of using it to improve the properties of the soil seems to be a very important issue.
The aim of the study was to determine the effect of the addition of waste coal sludge on changes in the sorp-tion capacity of the obtained composts.
The potential of using different substrates in the composting process is determined primarily by their proper moisture content, optimal C/N ratio and proper structure, forming an environment with good oxygenation. After theoreti-cal analysis and practical testing, several substrate combinations were selected for the study. The process was conducted using only basic materials (grass, organic fraction of municipal waste, structure-forming materials), and coal sludge in the amount of 10 and 25% by weight.
Since composting is a biological process, the course and conditions of the process need to be optimized and controlled. The research was conducted in two series: series 1, at room temperature of bioreactors, and series 2, with additional thermal insulation of bioreactors. The sorption capacity of the obtained composts was determined with reference to methylene blue and zinc sorption from aqueous solutions (the batch method) at a constant liquid-solid contact ratio of 1:20.
The most favorable process parameters and satisfactory quality of the obtained compost were observed in mix-tures with a lower proportion of coal sludge composted in bioreactors with additional insulation (series 2). In all com-posts produced with the addition of coal sludge, higher values of the specific surface area (St) with reference to meth-ylene blue were obtained compared to samples without added sludge. These composts also showed a high capability to remove zinc ions (above 92.9%), regardless of the type and proportion of individual substrates.
The obtained results confirmed the beneficial effect of 10% of coal sludge addition on the efficiency of the com-posting process, improvement of the sorption properties of composts, and the quality of the obtained final products.
Keywords
composting, coal sludge, sorption capacity
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