Industrial Wastewater MythBusters Part 1

Sunday, November 3, 2013

Dispel myths related to pretreatment, surcharges, sampling, and complex pollutants! This article is the second in a series that will discuss how wastewater myths can negatively impact compliance and operating costs at industrial facilities.  

Adding automation to a treatment system can reduce the time an operator spends on routine tasks.  However, the operator must maintain the automation equipment and know how to perform those tasks manually if automation problems arise.  If a facility becomes too dependent on the automation, they could lose the ability to operate the system effectively on their own.  When problems do arise, this can make troubleshooting and implementing corrective actions very difficult.

While this is always a great goal and worth careful consideration, it is never easy and in many cases not cost-effective.  Many zero-discharge technologies are extremely expensive from both a capital and operating cost standpoint.  There will always be residual waste streams with which to deal, and these can be very expensive to dispose of if they are regulated wastes.  Plus, many chemicals used in production processes and wastewater treatment can cause big problems with wastewater recycling technologies such as membrane filtration.  Also, the quality of water needed for your process may make recycling cost-prohibitive.  It is often better to focus on wastewater reuse opportunities, where existing treatment equipment can provide effluent for reuse in process areas that do not require high-quality water (cleaning, rinses, cooling, etc.).

The most expensive surcharge pollutant is typically biodegradable organics (BOD), and it can be surprisingly difficult (and costly) to remove with a pretreatment system.  If the BOD is soluble due to sugars, blood, alcohol, etc., then the only effective way to remove it is through biological treatment.  Biological treatment systems are very expensive from both a capital and operating cost standpoint, so much so that it would likely be more cost-effective just to pay the surcharge fees.  This is easy to evaluate using location-specific surcharge fees and rule-of-thumb estimates for biological treatment costs.

Grab sample results can be very misleading.  Since grab sampling is the EPA-approved method for some pollutants, including pH and oil & grease, compliance status is often based on a single sample result.  Often times, this does not give an accurate picture of compliance because a grab sample only represents the characteristics of process wastewater during the instant the sample is collected.  If process operations and sources of these pollutants vary substantially on an hourly or daily basis, then these pollutants may not even be present during most grab sampling events.  Grab samples should be representative of normal process conditions, so additional samples may need to be collected to determine your compliance status accurately.

Sulfuric acid is typically the default chemical for lowering wastewater pH in neutralization systems, but it isn’t the only option.  This heavily regulated chemical is effective but extremely dangerous.  Carbon dioxide is a great replacement for sulfuric acid because it is more effective on a pound-per-pound basis and much safer to use.  Carbon dioxide will not drop the pH below 6.0 s.u., so the overshooting and caustic corrections needed with sulfuric acid use are not an issue.  As a result, using carbon dioxide in neutralization systems will help to reduce operating costs, improve safety, and potentially eliminate the use of a chemical heavily regulated by both EPA and OSHA.