Worldwide media attention on arsenic in drinking water is also shedding light on the problem of arsenic in industrial wastewater. Arsenic is found in rocks and soil that can be released into the environment through geological events, such as volcanic activity and erosion. Some industrial processes, such as mining, smelting and the production of paints, metals, soaps, dyes, drugs, semi-conductors and wood preservatives, may also release arsenic into the environment.
Michigan wastewater remediation company, Great Lakes Carbon Treatment, was hired by a Kentucky refining company to assist their clean-up efforts for wastewater generated from cleaning barges used for transporting petroleum. The facility had a very advanced biological reduction system to break down the organics, but the problems with arsenic needed to be addressed.
As a solution, Great Lakes Carbon recommended the Bayoxide® E IN-20 iron oxide adsorptive media, with which the facility now treats an average of 70,000 gallons of wastewater per day. The water contains residual petroleum before treatment. A sequencing batch reactor is used to treat the residual petroleum, but the effluent going into the arsenic treatment system averages about 50 ppb of arsenic. This is above the contamination level; the effluent limit level is 20 ppb.
The lifespan of the media is approximately one year and over the course of that time, 20-21 million gallons of water are processed through the media.
Bayoxide works by binding the contaminant with ferrous compounds and making a colloid insoluble to water, so the harmful components are stabilized and the substance passes TCLP testing. Spent media can be safely sent to a landfill as a solid granular material.
"We were trying to find a solution with a very low labor-intensity and relatively low operational costs," said Great Lakes Carbon Treatment owner, Bill Pierce. "Capital costs are always high, but we struggled with justifying the cost to do a complete change-out of the media. Our cost ended up being approximately two tenths of a cent per gallon of water for processing; not bad at all, especially for something as dangerous as arsenic."
The main difference between treating drinking water for arsenic and treating wastewater is the level of the contaminants and the matrix of the chemistry involved. Ninety-nine percent of arsenic-contaminated drinking water comes from groundwater sources. When water is pulled from the ground, there are different ranges of iron, silica and other interferants in different parts of the world. But even with some variability, the result is a fairly consistent set of applications.
Wastewater treatment applications, however, are more varied and harder to predict. One plant may have high levels of phosphate contamination; the next may have high levels of metal contamination. Each wastewater application must be looked at independently.
Wastewater applications also tend to involve multiple treatment steps prior to achieving cleanup, while drinking water treatment is a relatively straightforward, one-step process. Arsenic wastewater treatment is a much more difficult application, but typically once drinking water regulations are determined, states and local authorities start to adopt drinking water standards for wastewater, and regulators start to develop tighter arsenic limits similar to those for drinking water.
Although the Bayoxide technology was developed for drinking water applications, it is also a tool that can be used for effectively treating wastewater. It's important to have other options such as biological treatment to do the pre-treatment, but if applied correctly, Bayoxide E IN-20 can be very cost-effective, providing the user with an assurance that he will be meeting his discharge limit every day.
For more information, email info@severntrentservices.com
[ x ] Close Window