Economical Solutions to Cleaning Industrial Settling Ponds

(Admin note: This article was submitted by invitation to discuss the issue of dealing with industrial settling ponds in an economical and environmentally-friendly manner.)

By: Greg Zellers, AWS Dredge

Discovering economical solutions to cleaning industrial settling ponds is always a concern. Both the coal producer and the end user have grappled with this for years. Coal ash, gypsum, coal fines and other solids collecting in lagoons can become real challenges. In the past, many methods have been used with varying degrees of success.

In recent years though, there has been an increasing need to dewater solids prior to disposal.

Belt presses and centrifuges have been around for years but have proven quite costly. Other mechanical methods of dewatering have also proven to be an inefficient use of both man hours and equipment.

An increasingly more popular dewatering method is the use of a geotextile tube system. This offers an economical and environmentally friendly alternative to conventional methods for sediment dewatering, containment of mining/industrial waste, sewage sludge and contaminated waste.

Since the late 1980’s, several thousand geotextile tubes, bags and containers ranging in sizes from 1 to 4000 cubic meters have been successfully filled with a variety of sludges and fill materials all over the world.

Compared to costly dewatering devices that require specialized transportation, cranes for set up, and high power consumption, dewatering tubes are fast and easy to transport. They are easy to set up and can be operational quickly.

Geotextile tubes are fabricated to exacting tolerances that allow them to be used for dewatering of contaminated sediments, fly ash, copper tailings and at numerous marinas, lakes and rivers. The effectiveness of geotextile tube dewatering is underscored by the fact that often the effluent is clean enough to be returned to the source. Often the sediment is treated with a polymer before entering the tubes. This accelerates the dewatering process. As the sediment enters the tubes, the sediment particles will flocculate increasing the size of the particle. The result of this chemical action is that the geotextile tubes dewater more rapidly and the discharged water has dramatically less solids.

A coal burning power-generating plant in Kentucky had a problem in which the sludge ponds that settled out of the scrubbings from the stack were full. The sludge was mostly lime and gypsum. It was being cleaned from the ponds with a long reach excavator, spread out to dry, and then hauled to a landfill. This process was not keeping up with the solids entering the pond. The excavator proved to be slow and there was not enough space available to dry the sludge. But the sludge could not be disposed of in the land-fill without drying it, some way. If something was not done the plant would have to shut down.

The sludge was pumped, with a dredge, into a 30 ft. circumference x 200 ft. long tubes. The project engineer indicated that the whole clean up costs were much less than he had anticipated. All three ponds were emptied into the tubes, dewatered and hauled to the landfill without a mishap.

These systems have been used in surface and deep mine applications throughout the world in conjunction with coal processing plants, process water, surface runoff, and mine site tailings.

Similarly, AWS Dredge, an environmental dredging and dewatering specialist, has cleaned many ash ponds and gypsum ponds in the power industry. Using geotextile dewatering tubes, AWS Dredge is now cleaning and dewatering a lagoon, at a major copper facility in the west that has become full of solids. By utilizing a system of floating dredges, pumps, and dewatering tubes, the sludges are being removed in a way that allows the ponds to remain in service.

But that is just the beginning. The copper producer is able to reprocess the captured solids, thus creating a windfall profit.

Since the project is in a highly regulated area, safety is paramount. AWS employees have received specialized, onsite training, to insure absolute compliance with all MSHA and site specific company policies.

AWS Dredge worked closely with the client to design the most efficient and cost effective plan based on the mine’s/processor’s needs. The plan includes dredging and dewatering “in-situ” copper sludge. The dewatered material will again be processed to be sold, rather than be wasted as can be the case in other operations.

AWS Dredge corporate headquarters is located in Benson Utah, has offices strategically located across the country, and has opened a new office in Tell City Indiana. Greg Zellers can be reached in Indiana at 812-608-1297 for your questions and inquiries.

06. April 2011 by Jason Hayes
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