THE EFFECTS OF PROPRIETARY CELLULOSE FIBERS ON THE DEWATERABILITY OF SLUDGE
Abstract:The economic and environmental price paid by society to dispose of wastewater sludge is already at distress levels in heavily populated, industrialized regions of the country and worsening as population and industry grow. Therefore, improving the dewaterability of wastewater sludge is, and must forever be, a national priority.
The paper presents the results of research conducted at numerous wastewater treatment facilities studying the effects of proprietary cellulose fibers on the dewaterability of sludge. The purpose of the study was to provide research that examines the impact of specially designed fibers on waste reduction, sludge throughput, polymer requirement, filtrate quality, belt blinding, clean-up, and maintenance.
The studies investigated the fiber technology's impact on sludge dewatered by belt filter presses, in the field, under various sludge conditions (i.e., mixtures of primary and secondary, straight secondary, and blends of secondary) and a variety of disposal means, including landfill, landapplication, incineration, and composting. In instances where regulation required lime stabilization, the fiber's effect on filter cake quality and lime consumption is addressed. Where composting was the disposal means, the technology's impact on amendment requirement, screening, and curing are discussed. Analyzes derived from operating and economic factors, and laboratory results provided by the management of the facilities' are included.
The studies compared the changes in the variables monitored, under the same conditions, with and without fiber conditioning. To accomplish this, a “control condition,” without the fibers, was established by the facilities' operator. In each case, the control condition was the optimum performance achievable under the prevailing site-conditions using procedures considered to be standard by the wastewater treatment industry.
The fibers were introduced into the sludge feed using two different methods, depending on the facilities' design. In batch-type operations where sludge was accumulated in a mix-tank prior to dewatering, a preferred amount of specially designed fiber was added directly into the mix-tank. In other situations, the preferred fiber was mixed into a slurry with water and then pumped into the sludge feed. All comparative analyzes are based on variable measurements, fiber dosages, and laboratory results provided by or confirmed by the facilities' operator.
Over twenty-five facilities were tested and evaluated. Those selected for presentation here represent a cross-section of the diverse sludge conditions and disposal means currently utilized by operators of wastewater treatment facilities. While pre-conditioning the sludge with the proprietary fibers was not economically feasible in all cases, the fibers did cause, in all cases, a substantial reduction in filter cake, less polymer requirement, reduced belt blinding, increased throughput capability, less clean-up time, and where lime stabilization was required, a better quality filter cake and less lime consumption. In other words, notwithstanding economic impact, which can vary depending on facility size and disposal cost, the study demonstrated that by conditioning the sludge with the proprietary fibers, dewaterability and environmental impact are significantly improved.
Since launching the technology four years ago, eleven facilities regularly use the fibers to reduce their cost to dewater and dispose of sludge. There has never been a facility that started using the fibers and stopped, and the list of new users continues to grow.
The technology studied is a leading-edge wastewater treatment technology that reduces pollutants and discharges into the environment — an innovative water pollution control technology that saves money and time. While the design of the fiber and its application are site-specific, it nonetheless appears reasonable to assume from the research that its use will significantly improve the dewaterability of sludge processed by belt filter presses, and thereby, significantly reduce environmental pollution and the economic impact of sludge disposal on society. Moreover, the technology's primary ingredient is recycled waste cellulose that otherwise could be deposited in landfills, a characteristic that compounds its beneficial contribution to our environment.
Document Type: Research Article
Publication date: 2000-01-01
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