Two plastic buckets sit in a corner of the Woodrat Water Treatment Plant in Bolinas. Both are filled with chlorine-treated water pulled from a reservoir operated by the Bolinas Community Public Utility District, but one of the buckets also holds a small dose of a coagulant called aluminum hydrochlorate. In a few weeks, shift operator Lewie Likover will test the water to see if the coagulant reduced the amount of disinfection byproducts, DBPs, which are potentially carcinogenic substances that form when chlorine combines with microscopic organic and inorganic materials such as dissolved dirt.
“I’m sure it’s going to reduce it,” said Mr. Likover, who returned to the district on a part-time basis soon after retiring in 2013 in order to oversee the district’s DBPs reduction project. “I’m not sure if it’s going to reduce it enough.”
The buckets represent one of the first steps for a pilot project that the district launched in May to devise a cheap, efficient and effective way to reduce chlorine DBPs and, in doing so, to come into compliance with regulations set by the State Water Resources Control Board. When quarterly data was last compiled, in April, the level of byproducts in the district’s water exceeded stringent benchmarks instituted by the federal Environmental Protection Agency in 1999 and regulated by the state.
Over the years, the district has tried a number of different methods to reduce DBPs, including aeration, granulated activated carbon and the same type of nano filtration technology that the Inverness Public Utility District fully implemented last December. But the coagulation method that the district is testing now, Mr. Likover said, is the cheapest by far: just several hundred dollars plus an uncertain expense for possible facilities upgrades, compared to the estimated $728,000 total that Inverness spent.
“This would be relatively inexpensive,” Mr. Likover said. “The only problem would be it would take time to get staff trained.”
Water pumped from the Arroyo Hondo Creek in Bolinas or the district’s two reservoirs enters the treatment plant off Mesa Road and circulates through a series of pipes before being pushed into one of four Siemens treatment units. There, the pressurized water is squeezed through several cylindrical filters packed with thousands of thin, perforated tubes that can clean up to 40 gallons of water per minute. That water is held in a large black tank, transferred through another pipeline and then injected with chlorine, on its way to pipe mains that distribute drinking water throughout the town.
With a process called direct coagulation, however, water is treated with aluminum hydrochlorate before reaching the treatment units and meanders through four 80-foot-long pipes. As the water winds through the pipes for a few minutes, the coagulant pulls out dissolved organic matter to form larger—though still minuscule—residual clumps, some of which the filters can catch. After passing through the filters, the water contains less organic matter when it’s chlorinated; thus, fewer DBPs are created. (The still-turbid wastewater full of organic matter is, ultimately, backwashed into the reservoir.)
None of the test water, Mr. Likover stressed, is entering the Bolinas drinking water supply at the moment; it’s all disposed back into the reservoir. And should the state approve the coagulant system, the district will have to develop an additional process for removing the coagulant’s aluminum traces from the water before it heads into town.
So far, Mr. Likover has only tested reservoir water, though a preliminary test in late May resulted in a 50 percent reduction of the organic carbon in the water—a promising start. Much of the byproduct problem arises from the reservoirs, whose water is cluttered with organic material. But the district seldom—once a year, perhaps—has to draw from the reservoirs to meet the town’s water demand. The vast majority of drinking water originates from Arroyo Hondo Creek, which sees surges in organic matter from rains.
The next step in the pilot project, then, will add the coagulant to creek water pumped into the plant after winter rains. Meanwhile, Mr. Likover will be busy tweaking the coagulant dosage amounts, hoping to strike the most effective and cost-saving blend.
“You have to be sure that any particular treatment option that you’re choosing to employ is going to work on all your water sources all the time,” said Jennifer Blackman, the district’s general manager. “What we’re trying to do is fully analyze the effectiveness of the coagulants on all the water sources during all times of the year.”
Ms. Blackman added that state approval for a byproduct-reduction system has gone slowly, given that regulators tend to focus on larger districts such as Marin Municipal Water District, which uses ammonia, and North Marin Water District, which has groundwater sources that contain less organic matter.
For its part, Inverness water operators have been pleased with the job done by their district’s new nano filtration system, the first of its kind to be brought fully online by any water agency in California. That filtration—designed by the same consultant who is now working with Bolinas, Jonathan Van Bourg—has achieved DBP levels far below state thresholds.
“It’s working great,” said Scott McMorrow, I.P.U.D.’s general manager. “It’s doing exactly what we thought it would do.”
In the event that direct coagulation does not pan out, Mr. Likover said, Bolinas may revert back to nano filtration. That method, he said, could be the most thorough treatment process for creek water, and perhaps the best overall method were it not for the high costs and a few technical glitches that the district encountered during a previous pilot project.
For now, he plans to run more tests on the water to make its color—an indication of turbidity and organic matter—as clear as possible until state regulators feel comfortable giving the green light. And while some old-school operators, he said, might consider the state’s standards too tough and unnecessary—lab animals have been the only subjects used to determine whether disinfection byproducts may be carcinogenic—Mr. Likover has his sights set on giving Bolinas the cleanest water possible.
“I probably prefer to drink water that doesn’t have byproducts with chlorine attached to it,” he said. “I’m all for clean water.”