Wastewater disposal requires various techniques to meet federal regulations
Jun 1, 2002 12:00 PM
JOE BROWN of the WCM Group Inc, Humble, Texas, urged tank cleaning managers to determine the hazardous materials content of wastewater as part of any program to meet environmental regulations. “Is the waste on the hazmat list, and if not, how do you know it's not,” he asked those attending the NTTC Tank Cleaning Seminar. “If you don't do the determinants, everything else just falls apart.”
Brown, Bruce Bishkin of APSI Inc, Elmhurst, Illinois, Jim Miller of Vopak Industrial Services USA, Houston, Texas, and Frank Dimalanta of Ethel M Chocolates, Henderson, Nevada, offered overviews about wastewater disposal techniques and regulations, as well as other environmental considerations.
Brown pointed out that disposing of wastewater is but one step in the handling process. He recommended that facility floors and yard areas be checked for leaks and contamination in order to protect property value. He also alerted wash rack managers to stiffer requirements for boiler emissions that now are in effect in Texas and California. These regulations also are on the horizon in many other states. “This is something that is up and coming,” Brown said. “If you are planning a new boiler purchase, you will want to take this into consideration.”
Another topic, storm water regulations, poses still more concerns for managers. Every state has different storm water regulations, which has limited involvement. “That's probably going to change,” he added. “I would expect to see a little more federal enforcement for this regulation.”
“Some of the concentration limits of pollutants are pretty extreme, and not necessary, in my view,” said Bishkin on the subject of handling rinse water to meet regulations. He noted that several standard technologies are used in the tank wash industry to process spent rinse waters. They include rotary precoat vacuum filter, cross-flow ultrafiltration, dissolved air flotation, and batch sedimentation.
The last technique has been used successfully with batches up to 8,000 gallons that can be treated in three hours. With a batch sedimentation process, windows in the tank make it possible to see the sludge. The tank is equipped with a filter press.
If any of the standard processes fail to meet the limits, carbon filtration or chemicals are used as a last resort with extremely variable results. Bishkin reminded managers using the carbon filtration to treat only crystal clear water, change the carbon often, up to once a week, and continuously test the water. “It has to be crystal clear,” he said.
Chemical oxidation is another alternative in case the standard technologies are not effective. However, it is not very effective and suffers from inconsistent results. The water should be crystal clear before adding the oxidants, or the process will likely fail. It may require 100 times more oxidants than is calculated.
Other technologies that have proved effective include incineration and evaporation. In addition to being very expensive, Bishkin pointed out that using incineration or evaporation without condensation may require an air permit. He discussed a technology — mechanical vapor recompression — that recovers the condensate, thus eliminating the need for air permitting, and recycles the heat of the evaporation. This dramatically reduces operating costs.
Looking to the future, Bishkin discussed a system incorporating the mechanical vapor recompression that includes initial pH adjustment followed by clay filtration of the condensate for reuse, and concentration of the pollutants for off-site disposal.
When tank cleaning facilities prefer not to handle their wastewater, Vopak offers an off-site treatment service, says Miller. Vopak facilities provide biological, physical, chemical, and solidification treatment processes. A laboratory on site provides treatability studies, waste characteristics determination, and metals screening.
For a look at a state-of-the-art wastewater handling, Dimalanta discussed the 32,000-gallon-per-day process used at a candy-manufacturing facility. Live bacteria, called The Living Machine, is used in treatment of the waste from the factory. All wastewater, with the exception of the bathrooms, is processed internally. Bacteria and percolated air are added initially to the water, which then is pumped into tanks that contain snails, fish, and plants.
From the treatment tanks, the water flows through constructed wetlands on site that allow the water to run underground through rocks. Eventually, the water can be released into streams. Solids are collected and made into compost.
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