WASH RACK operators were reminded that they are required to submit a baseline monitoring report on their effluent discharge to the local publicly owned wastewater treatment works (POTW), and it was due by March 12, 2001. The report is part of the new Transportation Equipment Cleaning-Effluent Limitation Guideline issued in 2000 by the Environmental Protection Agency (EPA).
Jack E Waggener, an environmental consultant with Dames & Moore, delivered the reminder as part of an update on the Effluent Limitations Guideline final rule. He spoke April 10 during the National Tank Truck Carriers Tank Cleaning Council seminar in San Antonio, Texas.
“We realize that some POTWs are accepting a pollution management plan (PMP) in lieu of the baseline report,” he said. “However, the baseline report is a federal requirement, so go ahead and do it. It's proactive for your operation, and it's easy to assemble.”
More Deadlines
Another important date to keep in mind is September 13, 2003. This is the deadline for full compliance with the regulation. Most tank wash racks fall under the rule as indirect dischargers, because they release their treated wastewater to a municipal sewage plant. Data gathered by Waggener and NTTC suggest that just a handful of wash operations are classified as direct dischargers.
Waggener said he believes the pollution management plan will be the best compliance option for most tank cleaning facilities. A few companies will opt for numerical limits, and some will use both systems.
“Most POTWs will work with you on all of this,” he said. “Wash racks are not required by the regulation to provide both a PMP and numerical limits program, but they may want to do so if that will keep a POTW happy. It's all negotiable.”
Documentation and recordkeeping are key elements in the PMP approach. Wash rack operators will need to monitor the volume, content, and characteristics of cleaning chemicals. They need to develop procedures for heel management, prerinse/presteam, and cleaning agents. They must document operator training and develop a waste minimization plan.
Compliance Materials
NTTC plans to provide its member wash racks with a packet of compliance materials to make it easier to put together a plan. It will include a sample PMP, general verbiage that can be incorporated into a facility's plan, specific limits guidelines, and the much-delayed EPA guidance publication.
The guidance document can be used by both wash racks and POTWs to interpret the regulation. It was supposed to be published before the baseline report was due but was so flawed that it was sent back for rewrite, according to Waggener.
In addition to the compliance packet, NTTC is updating its Cleaning Facility Audit Form to include details relevant to the Transportation Equipment Cleaning-Effluent Limitation Guideline.
One outcome of the new effluent treatment regulations is that the various systems used in the process will be getting more attention. Wash rack operators will be scrutinizing systems closely to determine what it will take to achieve regulatory compliance.
Treatment Technologies
Panelists at the NTTC Tank Cleaning Council seminar reviewed a variety of treatment technologies, including bioremediation, dissolved air flotation (DAF), flocculation anionics and cationics, oil and grease separation, and ultrafiltration.
Biological treatment of wastewater generates consistent results if the process is managed properly, according to Joe Brown, The WCM Group Inc. The downside is that it can take at least a week to fix a problem with a biological system.
“You need to physically control the process; to control the amount of food that reaches the bacteria,” he said. “It's important to control pH, temperature, and oxygen level. The treatment plant operator must continually observe the system.”
The best results can be achieved when a biological system is used in a dedicated cleaning operation where the same kinds of wastewater are generated day in and day out. The greatest challenge for a biological plant is a commercial cleaning rack that produces wastewater with a wide range of components.
Biological wastewater treatment will be in greatest demand in areas where POTWs are not available, according to Gary Carroll, The WCM Group. Biological systems can achieve as much as 96% efficiency.
Chemical/physical systems are the preferred choice in many cases, though. Advantages of the chemical/physical treatment approach is that the equipment takes up less space and operators need less training. These systems include a variety of components such as collection tanks, equalization tanks, oil and grease skimmers, and filtration.
A chemical/physical wastewater treatment system can be assembled for $150,000 to $200,000. Units for pH adjustment cost $10,000 to $12,000. A sludge tank and pumps run $20,000, and equalization tanks are $30,000 to $50,000. A DAF system runs $50,000, and a filter press can cost about the same.
DAF is a very effective method for reduction of suspended solids, oil and grease, metals, biological oxygen demand (BOD), chemical oxygen demand (COD), and volatile organic compounds (VOCs), according to Van Dalton, Pump Systems Inc. System capacities range from 50 to 800 gallons per minute.
In a DAF system, wastewater treatment starts in the containment pit. It is pumped to an equalization tank with pH monitoring capabilities. Acid or caustic is injected into the waste stream to bring the pH level into tolerance.
The pumps must be capable of passing solids up to 2.5 inches in size. Dalton recommends Gorman-Rupp pumps. The equalization tank should have a two-day capacity, and it must have mixing capabilities that thoroughly circulate the waste solution every 90 seconds.
Pipe Flocculator
En route to the DAF tank, wastewater flows through a pipe flocculator. It allows precise injection of controlled amounts of air and treatment chemicals. Microscopic air bubbles attach themselves to the flocculated particles in the pipe flocculator and create buoyant particles.
Next stop is the DAF vessel, which is typically fabricated from steel, either 304 stainless or carbon with a polyurethane coating.
As the flocculated wastewater enters the DAF cell, it flows evenly throughout the vessel. Flocculated solids rise rapidly and accumulate on the surface of the DAF cell and are skimmed into the DAF float storage sump. Skimmed solids are then ready for dewatering.
Cleaned, treated water can be released to the city sewer. Alternatively, the water can be polished, recycled, and reused in the tank cleaning operation.
Treated solids are moved to a filter press for dewatering. Filter options include diatomaceous earth or plate systems. Sludge cake can be taken to a landfill for final disposal.