Treatment & Removal of Hexavalent Chrome & Other Heavy Metals
Jan 19, 2018
Managing industrial wastewater treatment equipment often takes a back seat to production equipment. I Industrial companies are finding out the hard way that hauling wastewater costs much more than utilizing a wastewater treatment system.
Water pollution control is not a money maker, which could explain its historic neglect in maintenance and capital expenditure. However, if the cost-saving benefits provided are clearly outlined, environmental technologies might get the respect they deserve.
Maintaining effluent discharge compliance for metal hydroxides such as hexavalent chrome requires a two-step process: Chemical and Mechanical.
Step 1: Chemical Treatment
The chemical treatment consists of pH and ORP adjustment to transform hex-chrome into tri-chrome. There is a distinct color change from yellow (hex) to blue/green (tri). When hexavalent becomes trivalent chromium, the wastewater is pH adjusted to precipitate the metal. Precipitation is the physical separation of chrome from water; in essence, the dissolved metal becomes a suspended solid and falls out of its liquid solution. In some cases, a coagulant or flocculent is added (typically an anionic or cationic polymer) to increase the solid particle size so it can be filtered out.
Step 2: Mechanical Treatment
The mechanical aspect requires machinery to physically remove the chrome from the water. The non-potable effluent is discharged and the solid material disposed according to environmental regulations. In some instances, the filtered water goes through additional equipment for recycling purposes.
Dealing with chemicals and dewatering equipment is not child’s play; it requires more than a swimming pool filter and commands more respect than a garbage disposal. The steps to get from non-compliance to compliance require maintenance, resourcefulness and common sense. These qualities should not only be applied to production, but to the bottom line. In my experience, I believe the COO, CFO and EHS Managers should examine the benefits of an in-house wastewater treatment system, as they can save great amounts of money in disposal costs and potential lawsuits, fines, surcharges, and more.
It takes the assistance of an expert to properly treat wastewater
Hauling away liquid wastewater is an alternative that many maintenance managers find attractive. Fill a tank, call in a pump truck and remove the wastewater; no muss, no fuss… right?
To put this situation into perspective, one gallon of water weighs 8.34 pounds; the contaminated solids add to this weight (trucking companies charge by the ton). Chrome is hazardous, the liquid waste needs to be handled and disposed of at a specialized facility. These facilities can be miles away, sometimes located in another state! I installed an ALAR chemical treatment system with Auto-Vac® dewatering system at a company that hauled their chrome across state. They generated 5000 gallons per day and paid $1.00 per gallon to haul it away.
Let’s run the numbers:
5000 gallons per day x $1.00 per gallon = $5000 per day
$5000 per day x 7 days a week = $35,000 per week
$35,000 per week x 52 weeks per year = $1,820,000.00 disposal cost
ALAR: (Consumable Costs)
Chemicals + Utilities + Labor + Disposal = $0.10 per gallon
35,000 gallons per week x $0.10 per gallon = $3500.00 per week
$3500 per week x 52 weeks per year = $182,000 per year
ALAR Capital Cost (Equipment) = $160,000
Estimated savings per year (after capital cost is paid) = $1,638,000.00
When I approach a company and ask, “Do you have a wastewater problem?”, and they reply, “No. We haul away our wastewater”; then chances are... they have a problem they just haven’t done the math.
If a company is violating toxic chromium discharge levels, then they have a serious problem. Remediation costs, legal expenses and cease-and-desist production orders would pay for a wastewater system; so why not solve the problem at the source?
ALAR manufactures industrial water treatment equipment for worldwide distribution. Metal finishing wastewater is a moving target; no two waste streams are alike. ALAR understands the difference and uses its chemical, engineering and technological expertise to deliver results that work. Responsible metal hydroxide water management makes the difference between regulatory compliance and non-compliance. ALAR offers a variety of mechanical and chemical systems. Customers are welcome bench and pilot test the ALAR equipment to determine the most cost effective method of meeting effluent discharge limits.
ALAR Engineering Corporation is family [female] owned and operated; located in Mokena, IL. The National Minority Business Council, Inc. recognizes ALAR Engineering Corp. as a Minority-Owned Business.