Industrial Wastewater MythBusters
Friday, October 28, 2016
Wastewater myths can negatively impact compliance and operating costs at industrial facilities. This article is part of a series that will dispel myths related to pretreatment, surcharges, sampling, and complex pollutants.
“We don’t need a good pretreatment operator, just a warm body.”
Industrial pretreatment system operators must be qualified and trained appropriately for the equipment with which they will be working. They must understand basic chemistry and have a good working knowledge of mechanical and electrical equipment. Operators should use detailed log sheets to record critical system information, and managers should review these daily. These are critical both for operator performance evaluations and for system troubleshooting.
“If we add microbes to our wastewater, it will reduce our BOD surcharge fees.”
This approach works in home septic tanks only because of the long retention time provided. It takes several hours for microbes to start metabolizing BOD effectively. If you have a grease trap, equalization tank, or dissolved air flotation (DAF) system, you may be able to provide enough retention time for a significant level of BOD reduction. Use the products that allow for growth and multiplication of the microbes prior to injection into the wastewater so that you have a better chance of significantly lowering BOD. High temperatures and chemicals associated with process cleaning operations can kill the microbes, so adding them after some form of equalization is critical. Check with your POTW as some locations prohibit these types of products.
“Split samples will ensure the POTW’s results are accurate.”
While it is always worthwhile to check any regulatory agency’s work, split sampling can be expensive and provide little value. Laboratory techniques are standardized for all parameters, so different labs should all be using the same procedures. Typically, bad sample results come from a combination of other factors, including sample location, sampling procedures (unrepresentative grab samples), process upsets, or treatment equipment problems. None of these issues can be detected through split sampling. For surcharge split sampling, the analytical method for BOD has inherent inaccuracies that make comparing split sample results almost impossible. The POTW will never agree that your lower split sample results are more accurate, plus your results could end up being higher! It is better to observe the POTW’s sampling procedures carefully, make sure the sampling location/time is representative, and focus on proactive management of your processes.
“Wastewater pH has no impact on pretreatment, so we shouldn’t waste money on the chemicals.”
Wastewater pH has a big impact on pretreatment. There are specific pH ranges that are optimal for metals removal, oil & grease removal, and treatment polymer effectiveness. Equalization is a great way to wipe out large pH fluctuations that can be detrimental to most treatment operations and save money on neutralization chemical costs. Additional pH control at the front end of most pretreatment systems will improve reliability and compliance as well as provide cost savings from reduced polymers usage.
OIL & GREASE
“Oil & grease compliance is simple.”
Oil & grease compliance can be very confusing because this pollutant is defined and regulated differently by most POTWs. The most important things to understand is that total oil & grease (O&G or FOG) consists of two parts: an animal/vegetable or biodegradable fraction, and a petroleum or nonbiodegradable fraction. The animal/vegetable fraction is a concern for some POTWs because animal fats/greases can congeal in sewers and cause blockages, while the petroleum fraction can be toxic to the microbe population in the POTW treatment processes. Some POTWs establish a compliance limit only for total O&G, others have limits for one or both fractions, and some don’t have specific limits at all. In order to manage your compliance risks appropriately, it is critical to know how O&G is defined and regulated by your POTW. It is also important to know sources of O&G that are present in your processes. For food processing facilities, the animal/vegetable fraction is seldom overlooked, but the petroleum fraction may also be present from lubricants used in production conveyor systems. Do your due diligence and look for O&G everywhere in your process.