Polk County Utilities reports two wastewater spills. The first was a 376,000-gallon spill.

LAKELAND — Twice last week, Polk County Utilities filed reports to state regulators about spill incidents at the Southwest Regional Wastewater Treatment Facility in Mulberry.

The first was a 376,000-gallon spill of effluent to the ground. In the second incident, 8,415 gallons of sludge oozed from a manhole cover at the facility.

Both met the criteria for reporting the incidents to the Florida Department of Environmental Protection, which had distributed the publicly available notices of pollution.

FDEP requires utilities to report spills of 1,000 gallons or larger.

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The notice on Jan. 11 concerning the original spill stated, “An effluent reject storage tank overflowed at the facility resulting in a discharge of approximately 376,000 gallons onto the ground.”

For comparison, the 376,000-gallon wastewater spill would fill nearly 13 swimming pools of an average depth of 6 feet.

Or, in cubic feet, the spill would cover a football field – which is approximately one acre – at a depth of about 1.1 feet, according to civil engineer Bonneau Dickson, who is a Berkeley, Calif. resident and frequently testifies as an expert witness in sanitary sewerage treatment trials.

“376,000 gallons is a lot,” Dickson said, adding that the U.S. Environmental Protection Agency estimates the average wastewater spill to be about 10,000 to 20,000 gallons.

Due to Florida’s sandy soil, most of the wastewater spill would have drained into the ground, possibly overnight, he said.

“Soil is a very good filter,” Dickson added.

The incident at 2000 Fourth Street began on Jan. 9 at 11:30 p.m. and ended on Jan. 10 at 6:30 a.m., the DEP notice stated.

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The effluent was characterized as treated wastewater or used water from indoor residential and commercial customers that is received through the collection system, said Polk County utilities director Tamara Richardson in an email statement on Friday.

The FDEP issued an updated notice Friday to explain the cause as “a faulty reading from a sensor in the aeration bay. The sensor has since been recalibrated and is now functioning properly.” The original DEP notice stated, “The discharge did not enter any surface water bodies and did not pose a potential risk to the public health, safety or welfare.”

“The spill flowed into the onsite stormwater pond and percolated into the ground,” Richardson explained. “This does not present a health hazard as the site is restricted from public access.”

Second incident at the Southwest Regional Wastewater Treatment Facility

In the second incident that started Monday at the Southwest Regional Wastewater Treatment Facility, the FDEP notice stated, "An estimated 8,415 gallons of waste activated sludge overflowed from a manhole onto the plant site."

About 1,000 gallons of the sludge flowed to the on-site storm water pond and was contained within the facility property, according to the notice.

Further, approximately 5,400 gallons was recovered and properly disposed of and utility workers applied lime “to the affected area for disinfection” and “the storm water pond will be sampled upon completion of the remediation,” the notice stated.

Also, according to the notice, in both cases the discharge did not enter any surface water bodies and “did not pose a potential risk to public health, safety, or welfare.”

Neither wastewater nor reclaimed water service was interrupted due to the incidents, Richardson stated in her emailed response.

Regarding the wastewater spill, she noted, “Although this sensor is recalibrated regularly and this appears to be a unique and isolated incident, the operators are considering increasing the frequency of calibration of the sensor to avoid the possibility of a recurrence.”

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“The spill flowed into the onsite storm water pond and percolated into the ground. This does not present a health hazard as the site is restricted from public access,” Richardson said.

Each of the facilities’ two-million-gallon effluent storage tanks is made of prestressed concrete and provides ground storage for reclaimed water, potable water or rejected reclaimed water for future use or additional processing, she said.

The rejected reclaimed water had no odors, so there were no complaints of a smell. There are nearby wetlands, but none of the effluent entered the local water or private property, Richardson explained.

The treatment plant is bordered by the Prairie Cemetery, a residential neighborhood along Third and Fourth streets and an industrial area.

The water treatment process has multiple steps, and the facility is managed by licensed operators, Richardson stated. Once the process is complete per state regulations, reclaimed water can be returned to homes and businesses for irrigation, industrial uses and other non-drinking water uses.

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Following the wastewater spill, recoverable effluent was returned to the headworks, the first step in the treatment process at the treatment facility to be reprocessed, she said.

Polk County Utilities owns and operates three regional public access reclamation treatment facilities, including the Southwest Regional Wastewater Treatment Facility and four smaller wastewater treatment facilities.

In all, the county maintains over 616 miles of sewer pipe – both force main and gravity main – throughout the county. It manages nearly 400 lift stations.

Wastewater and sewer collection service is provided to approximately 12,821 homes and business in the Southwest Regional Utility Service Area. Reclaimed water service is provided to 2,224 homes and businesses in the area and to TECO’s Polk Power Station.

Paul Nutcher covers business and industry for The Ledger. He can be reached at pnutcher@gannett.com.

This article originally appeared on The Ledger: Polk facility spills gallons of wastewater twice in in Mulberry