In rare move, authority to ease sewer pollution limits

John Howell
Posted 11/25/14

Imagine as a business being required to treat wastewater to a higher standard than when it came out of the tap.

That’s been the case for the pH range of wastewater flowing into the Warwick …

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In rare move, authority to ease sewer pollution limits

Posted

Imagine as a business being required to treat wastewater to a higher standard than when it came out of the tap.

That’s been the case for the pH range of wastewater flowing into the Warwick wastewater treatment plant for years. Commercial and industrial users of the sewer system are presently required to meet a range of 6.0 to 9.0 when, in fact, water straight from the tap tests at 10.0.

That range would change from 6.0 to 10.0 if the Warwick Sewer Authority adopts proposed changes in the industrial pretreatment program limits. Amendments in the limits that have gained Rhode Island Department of Environmental Management approval after two years of review will be outlined at a public hearing on Dec. 18 from 2 to 3 p.m. at sewer authority offices located at 125 Arthur Devine Blvd.

The limit on pH won’t be the only change. Limits on nine pollutants could be removed entirely, or relaxed, in what represents significant cost-savings to businesses and, one of those rare instances where less rather than more, is required to meet environmental standards.

“You never see less stringent limits,” said Janine Burke, executive director of the Warwick Sewer Authority.

Burke credits Betty Anne Rogers, who runs the plant’s laboratory and is the WSA pre-treatment coordinator, for conducting a thorough analysis of plant operations, determining its capability to remove pollutants and then showing DEM the limits could be changed without jeopardizing the environment.

Rogers said the limits being used are somewhat arbitrary and have required businesses to implement measures that, in some instances, don’t make sense and actually impede the process of treating wastewater.

“The [limits] are so much more scientifically derived and so much more positive,” she said in an interview last Thursday.

Robert DiSaia, DEM’s coordinator of the industrial pre-treatment program, said yesterday some of the criteria for limits date back to the 1990s.

“They used Mid-West cookbook type of examples,” he said of some limits that apparently had little relevance to conditions. “It was not as scientific as it is now,” he said.

As for requirements to reduce pH, DiSaia said, “When you look at it from a common sense point of view, it doesn’t make any sense to require industry to change the pH when someone washing their hands doesn’t have to.”

He said DEM issued preliminary approval of the revisions on Oct. 22. Following the hearing and assuming approval by the authority, DiSaia said final DEM approval could come in late January or early February.

One limit that would be removed, which would affect the pretreatment of wastewater from food service companies, is BOD, or biological oxygen demand. The maximum daily current limit is 1,000 (mg/l).

Actually, explains Rogers, the treatment plant “needs more food to come in.” The food feeds the microbes or “good bugs,” as they are called, that remove (eat) pollutants and clean the wastewater.

The change would also lift limits on COD, or chemical oxygen demand. Both BOD and COD limits would be replaced by a new limit of 2,500 mg/l maximum daily limit on CBOD, or carbonaceous biochemical oxygen demand. Rogers points out industry will need to conduct one fewer test and the plant should see an increase in “food” for the good bugs.

As Rogers explained, she not only wanted to assess the relevance of limits set on industrial users of the system, but also the plant’s ability to treat those pollutants and its capacity to treat additional loads to meet the growth of existing customers and provide for new businesses.

The level to which industrial users have to pre-treat wastewater would lower the limits on chromium, nickel, silver and oil and grease. It would remove limits on antimony and thallium. A few limits would become more stringent including cyanide, mercury and beryllium. The changes would impact 650 companies that are required to test their wastewater and, if not meeting limits, pre-treat it.

“Our companies are very compliant,” says Rogers, “Rarely do we get a violator on local limits.”

She said the WSA has “positive relationships” with the city’s industrial users and has worked with them to meet requirements. She cites Vishay Americas Inc., which manufactures semiconductors as an example. She said Vishay was experiencing difficultly in removing cyanide from its waste stream. As cyanide and gold bond, Rogers suspected if the gold could be extracted it would reduce the cyanide.

“It was like flushing raw materials down the drain,” she said of the process being used.

Vishay installed a series of screening grids that quickly paid for themselves with the recovery of gold while dramatically reducing the level of cyanide.

Rogers also works closely with Advanced Chemical. She has outlined the proposed limit changes with the company.

“We don’t want to scare companies like Advanced Chemical out of the city. They’re a big company,” she said.

Wastewater from residences does not require pre-treatment, yet Rogers points out that as much as 50 percent of metals flowing into the system are from residential customers. Sources include cleansers, detergents and even shampoos and hair conditioners. Burke says the reduction in limits should serve to make Warwick more competitive to businesses.

Of all the limits, that on pH confounds her most. She said higher levels of pH are desirable in the water system as it reduces the level of acidity and corrosion on pipes and equipment. That is also true for the sewer system.

“They had to abide by it,” she said of businesses, “and that killed me and they were putting in chemicals to lower it, and then when it got here we’re looking to higher it to help with the bugs.”

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  • RichardLangseth

    That is very good news. But what about the stringent phosphorus discharge limits that the Mayor agreed to. This is costing the city millions in borrowing costs. Could they be relaxed? Since the discharge is a straight shot to salt water - no standing water in the river to speak of, this limit could be relaxed. But, I get nowhere whenever I discuss this limit.

    Wednesday, November 26, 2014 Report this