PITA Fiscal Year 2008 Projects - Environmental Technologies

Reduction In The Volume Of Arsenic-Laden Sludge Through Use Of Regenerable Adsorbent

Fixed-bed sorption processes have emerged as the most acceptable treatment for arsenic removal in both US and in the Indian subcontinent because they are operationally simple, relatively inexpensive and forgiving toward fluctuations in arsenic concentrations in contaminated groundwater. During the last ten years, we have extensively investigated sorption processes for arsenic removal in Asia and North America. In order to avoid future environmental crisis and long-term health impact, the currently practiced sorption processes must take note of the following critical issues and address them appropriately:

  1. Although sizes and physical-chemical properties vary, granules of iron oxide, aluminum oxide, titanium oxide or zirconium oxide are the arsenic-selective sorbents in nearly every affected location. In spite of their high arsenic selectivity, these inorganic oxide materials lack mechanical strength and resistance to attrition for prolonged fixed-bed operations. With time, these materials create fines and increase the head loss in the bed, thus necessitating frequent backwashing. During backwash, the fines containing high concentration of arsenic are routinely discharged in sewer/storm water lines or natural water bodies.

  2. The inorganic sorbents are also chemically unstable and hence, they are not amenable to chemical regeneration and reuse. They are essentially dumped after one use. The volume of arsenic-laden waste thus generated is quite high because the opportunity to regenerate and concentrate the waste is absent. This problem is particularly critical in developing nations where large landfills and hazardous waste sites are essentially absent.

Our research work during the last ten years has led to the development and commercialization of a durable polymer-based hybrid ion exchanger that is arsenic selective, regenerable and reusable for many cycles. Use of this new polymeric material can greatly overcome the shortcomings of granular inorganic oxides i.e., reduce formation of fines, eliminate backwash requirement during the process and drastically curtail the volume of disposable arsenic-laden sludge.

In this project, we will carry out laboratory studies and at the same time gather pertinent data from the Indian subcontinent to validate that the arsenic-selective adsorbent developed in Lehigh University and commercially manufactured by a Pennsylvania Co. (Purolite Co., Philadelphia) produces much smaller amount of sludge compared to other products currently available in the market.