- Created on Thursday, 03 July 2003 03:46
- Written by Mike Jacobs
The laundry industry, and more particularly, the individuals within, has the same aspirations for obtaining a cleaner, more environmentally friendly world as does the general population. Our children will inherit the environment that we are making today.At it’s heart, the laundry industry removes soil and dirt from laundered items to the water it is washed in, and then sends this wash water (effluent) to the local Publicly Owned Treatment Works (POTW). If the effluent does not meet the quality requirements set by the POTW for incoming water, then the laundry must pre-treat the effluent before it sends it to the POTW. This should lead to cleaner effluent that the POTW can properly treat. Most of the time this works, and works very well in protecting the waterways, and allows the POTW to function at maximum efficiency.
But there is at least one case where interpretation of a regulation (upper pH limits) is actually causing more problems than it solves. When upper pH limits are set too low by a local POTW, it usually requires laundries to inject acid into their effluent. Salts formed by the addition of acids used to lower the pH are normally water soluble, so they ultimately end up in the water released from the POTW, increasing the chemical load of the treated water released to the environment. There are many additional reasons why having a high upper pH limit is beneficial to both the environment and the pocketbook of the launderer and the POTW that will be enumerated here.
For many large industrial launderers, the difficulties of too low an upper pH limit in some locations has required adding large quantities of acid, usually sulfuric acid, to their effluent for many years. Current estimates are about 50,000 gallons of sulfuric acid are being needlessly used by large industrial launderers to lower the pH of the effluent stream leaving a laundry. The actual overall quantities for the entire laundry industry may be several multiples of that number. Further, all of the US industrial base that has alkaline effluent could easily be an order of magnitude greater than that number.
To add insult to injury, many local POTW’s must add alkaline materials to their incoming water because quite often the overall pH of the influent is acidic. This adds additional chemicals that ultimately end up in the water the POTW returns to the waterway.
USEPA Does Not Specify an Upper pH Limit
So why are upper pH limits set too low by some, but not all local POTW’s? It is because the United States Environmental Protection Agency (U.S. EPA) has not specified an upper pH limitation in the regulation that governs pH limits (40 CFR x 403.5 (b)(2)). The regulation does specify a lower pH limit (5.0) since lower pH’s can cause corrosive structural damage to POTW’s.
The U.S. EPA does not specify an upper pH limitation in §403.5 because alkaline wastewater has a limited adverse effect on POTW collection and treatment systems. The Agency has acknowledged that the "upper limit for the pH established in many sewer-use regulations is not based upon a realistic appraisal of the effects. The neutralization of high-pH wastes before discharge to the sewer is usually detrimental." While the U.S. EPA imposes no upper pH limit, most local pretreatment regulations or ordinances do limit the upper range for wastewater pH discharges.
The many benefits to having a high (12.0 or greater), or no upper pH limit have been instituted by many larger municipalities.
|Adam, OK||No upper limit|
|Birmingham, AL||No upper limit|
|Curlpaper, VA||No upper limit|
|Ft. Worth, TX||12.0|
|LA County, CA||No upper limit|
|Milwaukee, WI||No upper limit|
|Orange County, CA||12.0|
|Portsmouth, VA||No upper limit|
|St. Cloud, MN||12.0|
|San Jose, CA||12.5|
Alkaline (high pH) wastewater offers benefits to sewage collection systems (sewers), wastewater treatment plants, and worker health and safety as follows:
- Benefits To Sewage Collection Systems
High-pH wastewater is typically not detrimental to the structural integrity of the sewer. When attempting to neutralize high-pH discharges, a sewer can be damaged by the accidental release and/or over-addition of pH adjustment chemicals (sulfuric acid, hydrochloric acid, etc.). The presence of high-pH wastewater helps to prevent damage from such incidents (alkali neutralizes acid). In addition, high-pH wastewater actually prevents odors and corrosion due to hydrogen sulfide gas as it limits the amount of dissolved sulfide available in the wastewater thus making it unavailable to escape into the sewer’s atmosphere.
Continuous addition of strong alkalies to the sewer to obtain these benefits is generally neither practical nor cost effective. The same benefits can be attained—at no cost—by not mandating that industrial users (in our case launderers) lower wastewater pH before discharge to the sewer.
- Benefits To Wastewater Treatment Plants
A higher pH at the industrial user's point of discharge reduces or eliminates the need for adding caustic at the POTW to maximize treatment system removal efficiency. Neutralization of a high-pH wastewater with acid solubilizes metals. The addition of alkalinity through high-pH wastewater helps keep the pH within the acceptable range for activated sludge treatment operations. It also reduces the solubility of metal ions and thus metal-caused inhibition that can sometimes happen in a wastewater treatment plant’s biological treatment systems (activated sludge units and aerobic and anaerobic digestion units.)
Increasing an industrial user's upper pH limit is a win-win proposition that can provide environmental benefits at no additional cost to either the launderer or the POTW. It may even be a money saver, as the cost of adding alkalinity to a POTW’s biological treatment system to maintain optimum performance can be reduced or eliminated altogether.
- Benefits To Worker Health and Safety
Unnecessarily neutralizing an industrial user's high-pH wastewater increases the potential for harm to humans. The neutralization of high-pH wastewater with an acid can create health and safety problems for an industrial user’s treatment system operator. Sulfuric acid, the acid of choice, is used in a concentrated form that can cause significant damage to a person's skin, eyes, and other membranes. Though all operators are provided with and are schooled in the proper use of safety equipment, accidents still can and do occur.
Why Don’t All POTW’s Adapt a Higher Upper pH Limit?
It would seem that such convincing evidence would cause all wastewater treatment plants to act appropriately, and as noted above, some already have increased their upper pH limits. But it is also true that changing the status quo presents it’s own problems. Lack of a straightforward guidance from the U.S. EPA on why higher upper pH limits are beneficial seems to be the greatest hindrance to seeing wholesale increases to upper pH limits across the country. To this end, the Uniform & Textile Service Association (UTSA) has worked hard to document the science behind why a higher upper pH limit is so beneficial. UTSA is now in contact with the U.S. EPA, and with the science in hand, is trying to convince them to issue a straightforward ruling on why higher upper pH limits are better. Once that is accomplished it will be much easier for a launderer, and for that matter any industrial user, to request a higher upper pH limit.
Many thanks to the Uniform & Textile Services Association (UTSA) for the data used in this article. For further information on this important subject go to www.utsa.com and search for the phrase “upper pH.”
Mike Jacobs has been with Gurtler Industries, Inc. as the Director of Technical Services for 15 years. He is currently on the UTSA Environmental Committee.
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