Use of a textile wastewater sludge as a supplemental solid fuel

Abstract

The dried sludge by-product generated by the wastewater treatment system at a textile dyeing and finishing facility in southwestern Virginia is currently disposed of in a conventional landfill. This method represents not only a substantial annual cost, but also a potentially serious environmental risk. An investigation was conducted at this facility with the goal of finding an alternative use or market for this by-product of textile manufacturing. After an extensive literature search and initial analyses, the feasibility of using the by-product as a supplemental fuel in the facility's coal boilers was investigated.

Proximate analyses showed that the by-product, with a relatively high heating value and low sulfur content, was fairly well suited for use a supplemental fuel. A brief test-burn of the by-product in one boiler resulted in no observable change in boiler operation or efficiency. Following a conversation with representatives of the Virginia Department of Environmental Quality, a list was formed of the potential air pollutants which are of particular concern when considering combustion processes. Subsequent chemical analyses and mass balances showed that burning the proposed fuel mixture would release acceptably small amounts of a majority of these pollutants. The only pollutants which represent a potential problem are two heavy metals -- chromium and nickel. Additional laboratory testing helped to locate major sources of these elements within the plant. The concentrations of these metals in the final by-product are expected to be reduced to some extent by future source-reduction efforts.

It is recommended that the information contained in this report be used to complete an application for an air permit which would allow the facility to use the by-product as a supplemental fuel in the plant's coal boilers. If this permit application is approved, significant cost savings will be realized not only from the reduction in landfilling costs, but also from a reduction in coal usage. It is further recommended that these cost savings be used to investigate further waste reduction and process optimization measures.