Colfax required to meet lower phosphorus limits for new wastewater permit

By LeAnn R. Ralph

COLFAX — By the time 2017 rolls around, the village’s new wastewater permit will require Colfax to discharge about eight times less phosphorus than is currently being discharged.

Paul Gont, the village’s wastewater engineer with Short Elliot Hendrickson (SEH), reviewed the village’s draft Wisconsin Pollutant Discharge Elimination System (WPDES) permit with the Colfax Village Board at the January 13 meeting.

 The permit, which is issued by the state Department of Natural Resources, is expected to go into effect April 1 and to expire March 31, 2019.

Phosphorus discharge has been a problem for Colfax for many years.

The village currently discharges between eight and ten milligrams of phosphorus per liter of wastewater.

By 2017, the permit will require the village to discharge 1.5 milligrams of phosphorus per liter at a discharge rate of 60,000 to 70,000 gallons per day or 1 milligram of phosphorous per liter at the design flow rate of 105,000 gallons per day.

Colfax discharges to the Red Cedar River, and the wastewater treatment lagoons discharge from May until November.

Phosphorus is the nutrient implicated in the toxic algae blooms every summer in Tainter Lake and Lake Menomin that turn the water into the color and consistency of green paint.

Last year, as part of a pilot study, Colfax used alum to treat the wastewater and was able to reduce the phosphorus to 2.5 milligrams per liter, Gont noted.

Alum binds with the phosphorus and causes the phosphorus to settle out into the bottom of the lagoons.

The lower phosphorus limit is part of the Total Maximum Daily Load (TMDL) for phosphorus that the DNR established for the 1900-square-mile Red Cedar Watershed.

Phosphorus run-off from the entire watershed drains into Tainter Lake and Lake Menomin, and the phosphorus from Colfax is only a small percentage of the entire phosphorus load.

The soil in this area is naturally high in phosphorus, and water coming out of the tap in Colfax is already high in phosphorus.

Gravity

Alum was added to the lagoons last year using a gravity feed system, Gont noted.

Scott Gunnufson, village president, asked if running electricity out to the lagoons and then using an electrically powered system to feed the alum would be better.

If electricity was available out at the lagoons, then a chemical feed pump with a meter could be used to more precisely control the alum, Gont said.

Colfax also has solar-powered mixers out at the lagoons to keep the water circulating.

“It will be new territory to see how effective they are,” Gont said.

The village board’s public works committee obtained an estimate last year that placed the cost of running electricity out to the lagoon at around $7,000.

Phosphorus limits

The village’s new wastewater permit sets a new phosphorus limit of 4 milligrams per liter that will be effective as soon as the permit is issued this April.

From January 1, 2015, to December 31, 2016, the village’s phosphorus limit will be 3 milligrams per liter.

On January 1, 2017, the village phosphorus limit will be set at 320 pounds per year, which translates into about 1.5 milligrams per liter at 60,000 to 70,000 gallons per day or 1 milligram per liter at the design flow.

Pollutant trading

DNR officials initially told the Colfax Village Board that the village could use pollutant trading as a way to mitigate the amount of phosphorus discharged from the wastewater treatment facility.

Under pollutant trading, the village would have provided financial support for farmers upstream to implement conservation practices to reduce run-off from farm fields with an exchange rate of two pounds from farm fields for every pound of phosphorus discharged by the village.

Last year, the Colfax Village Board found out that pollutant trading was no longer an option that the DNR would allow.

Other ways that the village could deal with phosphorus discharge once the discharge rate is reduced as much as possible by other means, such as the application of alum, would be to submit a watershed adaptive management plan, Gont told the village board at the January 13 meeting.

A watershed adaptive management plan would be similar to the TMDL developed for the Red Cedar River Watershed, he said.

It would be cost prohibitive and not feasible for Colfax to develop a watershed management plan for the entire watershed, Gont said.

Pollutant trading also would become an option again once the village has reduced the phosphorus discharge, he said.

A third option would be a waiver if the cost to village residents for sewer services were above a certain level, Gont said.

The economic level for a variance is 2 percent of the medium household income. The MHI in Colfax is $37,273, and 2 percent of that would be $745 per year for sewer services of $186 per quarter, he said.

Several village board members noted that the village’s current sewer rates are nowhere close to the amount needed for a variance.

Almost all of the new wastewater permits in the state will have a new lower phosphorus limit, Gont said.

Sludge

As part of the wastewater permit requirements, Colfax also will have to do a sludge depth evaluation of the lagoons by December 31, 2015, Gont said.

Mark Halpin, village trustee, noted that the cost for any kind of maintenance never decreases and wondered if it would be more cost effective to remove the sludge now rather than waiting until it reaches a certain level.

If the sludge depth now is only four inches, it would be better to wait until it reaches a deeper level, Gont said.

The sludge would be spread on land to dispose of it, he said.

Several village board members pointed out the irony of land-spreading the sludge that will contain phosphorus because the alum has caused it to settle out of the water.

The phosphorus comes off of the land and will be spread back on the land, they noted.

Sludge can only be spread in certain, approved areas, and the places where the sludge is spread will be will be in areas where run-off will not be a problem, Gont explained.

Next step

Now that the DNR has developed a preliminary draft permit for Colfax’s wastewater treatment permit, the next step will be for the DNR to issue a public notice that the draft has been completed and then set a 30-day public comment period, Gont explained.

After the 30-day public comment period, DNR officials will review the comments and will then approve the draft and issue the permit, he said.