Treatment of iron contaminated liquids with an activated iron solids (AIS) process

Abstract

The present invention is a method and system for treating iron-contaminated water (e.g., mine drainage) using an innovative treatment approach identified herein as the Activated Iron Solids (AIS) Process. The AIS process is capable of oxidizing and removing iron as iron oxides from iron-contaminated waters (such as, mining-related discharge, groundwater, surface water and industrial waste streams) producing a clean effluent. The AIS process is performed in a single or multiple tank system in which a catalytic surface chemistry process increases the iron removal 1000s times faster than would naturally occur and 100s of times faster than existing arts (e.g., aerobic pond passive treatment). In addition, the AIS process can utilize inexpensive alkaline material (such as, pulverized limestone) where initial mine drainage alkalinity (mg / L as CaCO3) to ferrous iron (mg / L) ratio is less than approximately 1.7. Excess accumulated iron oxides are periodically removed from the systems using a waste activated iron solids (WAIS) system and is directed to an Iron Oxide Thickener where the iron oxides are further concentrated.

Description

RELATED APPLICATION [0001] This patent application is a continuation in part to a pending patent application, entitled, “A process and System for Treating Iron Contaminated Liquids” filed Jun. 3, 2003, Ser. No. 10 / 453,127, which claims priority from a provisional patent application entitled, “A Process and Device for Treating Iron Contaminated Liquids” filed Jun. 3, 2002, Ser. No. 60 / 384,680.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates generally to a device and method for and the treatment of iron-contaminated fluid (e.g., mining-related discharge, groundwater, surface water and industrial waste streams) and, more particularly, to an apparatus and method for oxidizing and removing ferrous iron from iron-contaminated fluid, including mine drainage, and producing an effluent substantially free of iron. [0004] 2. Description of the Prior Art [0005] Iron-contaminated water result from a variety of natural and anthropogenic processes with the...

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Benefits of technology

[0011] Alkalinity may need to be generated to complete the precipitation of oxidized ferrous iron where the source water alkalinity (mg/L as CaCO3) to iron (mg/L as Fe) ratio is less 1.7. The low pH (approximately 5 to 6) and/or high carbonic acid concentrations (PCO2 approximately 0.1 to 0.5) found in many iron-contaminated waters (i.e., mine drainage) results in the rapid dissolution of carbonate minerals (such as calcite), thereby producing alkalinity at concentrations higher than will typically occur in natural systems. A type of passive treatment, known as Anoxic Limestone Drains (ALD), has been found to pr

Problems solved by technology

Treating mine drainage is an expensive endeavor involving land, construction, materials, operation, maintenance and chemical costs.

Left untreated, mine drainage contaminants surface and groundwater causing impacts to their social, recreational and commercial uses.

The low-density solids slowly settle in large open water basins, which require frequent and costly maintenance to remove and dispose the accumulated solids.

Iron removal in passive treatment systems require much larger land areas (10 to 20 times greater) than chemical treatment, which can become excessive for high flow and / or high iron concentration mine drainage discharges.

In addition, iron removal in passive systems can be problematic with performance varying with season, influent flow and concentration.

The prior art does not address the unique solids content of AIS-treated fluids.

Ferrous iron oxidation is usually the limiting step in the iron removal from iron-contaminated mine drainage.

This occurs because (1) chemical treatment occurs at high pH were homogeneous oxidation is by far the fastest oxidation either with or without suspended iron oxide solids; and (2) passive treatment is a non-mechanical approach that does not allow for the suspension of high concentrations of iron oxide (>200 mg / L) that would be needed to have heterogeneous dominated ferrous iron oxidation.

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