Many industrial manufacturing processes produce wastewaters containing heavy metals. Industries include printed circuit board manufacturing, metal finishing, automotive, aerospace, semiconductor manufacturing, electroplated metal parts/washing, textile dyes and steel, to name a few. As a result of improper treatment prior to discharge, many dissolved metals have been found in harmful concentrations in groundwaters which are destined for potable drinking water. In small quantities, certain heavy metals are nutritionally essential for a healthy life, but large amounts of any of them may cause acute or chronic toxicity (poisoning).
The metals most often linked to human poisoning have links to learning disabilities; cancers and death are typically caused by copper, nickel, cadmium, chrome, arsenic, lead and mercury. Many of these metals are required by humans in trace amounts, but in larger, persistent dosages, these heavy metals become toxic when they are not metabolized by the body and accumulate in the soft tissues. Heavy metal toxicity can result in damaged or reduced mental and central nervous function, lower energy levels, and damage to blood composition, lungs, kidneys, liver, and other vital organs.
The most commonly encountered toxic heavy metals include:
Other heavy metals of concern include:
In addition to concerns for human health and the environment, an increased desire to reuse and/or recycle industrial wastewaters also requires that metals removal occur in order to meet influent water quality requirement needed by the manufacturing process and equipment.
Evoqua can offer a wide range of treatment technologies depending on the specific contaminant to be reduced.
Ion exchange is a proven technology with effective treatment results for the removal of dissolved metals. Evoqua Water Technologies offers permanent, hard-piped ion exchange treatment systems containing contaminant-specific treatment resins, as well as removable systems. Our service ion exchange approach integrates equipment and service option combinations, thereby minimizing a plant’s capital investment and reduces overall space requirements. The system components are selected based upon available manpower, space limitations, access limitation and the specific water quality required. Service ion exchange provides the ultimate flexibility to add or remove treatment capacity as your business grows or compliance limits change. If needs change, we can simply change the media types and/or tank size, thereby saving our customers significant capital expense.
Once exhausted, the exchange vessels are removed and replaced with fresh, DOT-compliant vessels and returned to service. Exhausted vessels are transferred to our central treatment and processing facility where the hazardous/non-hazardous contaminants are removed from the media/resin. Service ion exchange minimizes the need for handling and on-site storage of chemicals and wastes for improved safety and compliance at your site. This option also saves valuable manufacturing space while minimizing your maintenance and installation requirements.
Microfiltration technology also offers a cost effective and sustainable solution for removal of heavy metals in wastewater and for water reuse applications. The membrane provides for an absolute barrier to the passage of solids and therefore is capable of removing metals (and other contaminants) to their solubility limits. Evoqua's Memtek® microfiltration system incorporates proprietary crossflow tubular membranes which remove precipitated contaminants and produce a high quality filtrate suitable for discharge, or for feed to a reverse osmosis unit or other polishing technology.
Dissolved Metals Removal Technologies for Your Wastewater Treatment Applications:
Physical/Chemical Treatment Systems
Microfiltration Membrane Systems
Microfiltration System Reduces Heavy Metal Waste by Two-Thirds
Marathon Norco Aerospace located in Waco, Texas is one of the few manufacturers of rechargeable, nickel cadmium batteries for the aerospace industry. One of the production problems associated with the manufacture of rechargeable, nickel cadmium batteries is the use of a number of heavy metals. Two of the metals which can be problematic when it comes to waste disposal are cadmium and chromium.
The amount of heavy metal waste generated at the Waco facility categorized the plant as a "significant hazardous waste generator," which created costly off-site hazardous waste disposal and extensive record keeping and documentation. Since 1972, the plant has used a diatomaceous filter system to reduce the volume and concentrate heavy metals in the waste. The plant's hazardous waste production required transport from the plant of over 100,000 pounds per year.
Read Full Case Study