A Study on the Feasibility of Using Leachate of Open Dumps as Moisture in Composting Municipal Solid Waste

Abstract

With the increasing population and development of industries, solid waste disposal hasbecome a major issue in Sri Lanka. The most common type of disposal is open dumping inurban areas which causes many environmental and social impacts. Especially generatingleachate from open dumps has become a severe problem. Viable options for acceptable solidwaste management practices in economically developing countries include minimization,recycling, composting, incineration, and sanitary landfilling. Composting is the option that,with few exceptions, best fits within the limited resources available in developing countries.Composing has some advantages such as lower equipment and operating costs, woks inharmony with the environment, and results a useful product.

This study has been carried out in the Mithotamulla open dumping site located in WesternProvince, Sri Lanka in the intension of studying the feasibility of using leachate of opendumps as moisture in composting Municipal Solid Waste.

This paper presents the section of the research which deals with the objective of analysing thecomposting process performance indicators such as pH, C/N ratio, temperature and totalorganic matter at usage of water and different dilutions of open dump leachate (100%, 75%,50%, 25% and 15%- by volume) on compost piles as moisture and studying the physical,chemical and biological parameters of used open dump leachate and water in composting.

Biodegradable part of the receiving MSW to the Mithotamulla dumping site was separatedand mixed thoroughly in order to obtain preferable raw material for composting. A set ofcomposting piles containing six piles were made in similar dimensions. Water was added tothe first file(control pile) as moisture and a concentration series (100%, 75%, 50%, 25% and15% by volume) made from open dump leachate was added to the each of the otherremaining five piles respectively as sufficient to maintain the moisture content 60% in firstsix weeks and as 40% in next two weeks. Pile turning was done manually in every seven daysand the process was monitored in the active phase of the composting process; eight weeksperiod.

Temperature values and pile dimensions of each pile were recorded every day and otherimportant composting performance indicators; pH, Total Nitrogen, Total Organic Carbon,Total organic matter were analysed weekly. C/N ratio was calculated using obtained valuesweekly. Samples were taken from nine symmetrical points in various depths in each pile andfinally three composite samples were made from each pile for analysis in each week.Environmental temperature was also recorded every day.

Leachate sample collection was conducted during dry season of year 2013. All leachatesamples were collected from the collected leachate in the stream around the open dumpingsite in Mithotamulla and were stored at 4 oC for until used for analysis. Leachate analysis wascarried out four times in the research period as 2 months before composting, at the beginningof composting process, at the 4th week and at the 8th week of composting process. All theleachate samples were analysed for following physical as well as chemical parametersincluded temperature, pH, Electrical Conductivity, Total Dissolved Solids, Total SuspendedSolids, Total Solids, Chloride, Ca2+ content, Mg2+ content, BOD, COD, Sulfate, Total organicmatter, heavy metals and E.coli content. Some of the parameters of used water as moisture tothe control pile were also measured periodically similar to the leachate analysis whenpossible.

According to the obtained results, it can be concluded that leachate from open dumping sitecontains higher amount of inorganic as well as organic component which may causecontamination of groundwater as well as surface water and also soil. Mainly BOD, COD,heavy metal contents and E.coli content is very much higher than the permitted levels for thedisposal of landfill leachate.

Through the results of analysing the behaviour of process performance indicators ofcomposting, the highest percentage volume reduction (61.17%) of pile was recorded in theusage of 100% open dump leachate as moisture. And the highest reduction C/N ratio andTOM were recorded from the pile which used 50% and 75% leachate dilutions respectively.Temperature values of control, 100% and 25% piles were in the desirable range forthermophilic bacteria. And those of other piles have exceeded it.