2018-02-10 / News

Cleaning the Island’s Wastewater Is Goal at Treatment Plant

By Stephanie Fortino


With its network of tanks, basins, and pipes, the Mackinac Island Wastewater Treatment Plant is covered with a blanket of snow Friday, January 26. With its network of tanks, basins, and pipes, the Mackinac Island Wastewater Treatment Plant is covered with a blanket of snow Friday, January 26. Creating clean water is the mission of those who work at the Mackinac Island Wastewater Treatment Plant. Through a complex system of screening, filtering, disinfecting, and testing, the crew works to cleanse the water used by residents and visitors.

Making sure the plant runs smoothly are manager Jay Davis and operator Justin Gallagher.

“We are protectors of water quality,” said Mr. Davis.

He has been working there since 2001, and Mr. Gallagher is working his third winter. One or both of them must be at the plant almost every day to run tests or change flow charts, and one of them always has to be on the island in case of an emergency. Mr. Davis would like to hire another operator for the plant to provide more flexibility in scheduling, but the search, he said, has been complicated by the lack of available housing.


Justin Gallagher pours a chemical into a graduated cylinder during his daily phosphorus test Friday, January 26. The test takes about four hours, and has to be done five times a week to ensure the plant is properly cleansing the Island’s wastewater. Justin Gallagher pours a chemical into a graduated cylinder during his daily phosphorus test Friday, January 26. The test takes about four hours, and has to be done five times a week to ensure the plant is properly cleansing the Island’s wastewater. The Wastewater Treatment Plant underwent a $6.5 million upgrade in 2013, and more improvements can be made, including replacing the pump stations, many of which were installed around 1985.

In the event of an outage, the plant can tap into a backup generator.

The wastewater treatment process begins as soon as water goes down a drain or a toilet is flushed. Sewage flows from homes and businesses through a network of sewer pipes to pump stations, which send it to the plant, at the intersection of Stonecliffe Road and Annex Road, near the Mackinac Island Airport.


Wastewater Treatment Plant Manager Jay Davis stands outside near the aeration tanks where bacteria breaks down organic matter during the treatment process. Since the plant sees large fluctuations in flow, some of the tanks and clarifiers are shut down for the winter. Wastewater Treatment Plant Manager Jay Davis stands outside near the aeration tanks where bacteria breaks down organic matter during the treatment process. Since the plant sees large fluctuations in flow, some of the tanks and clarifiers are shut down for the winter. Treating wastewater involves complex chemical processes. Chlorine gas is used to remove pathogens and ferric chloride controls phosphorus and helps material coagulate to settle out of the water. The effluent, which is the treated water pumped into Lake Huron at Biddle Point, must not have too much phosphorus and oxygen, which would promote algal blooms.

Sewage enters the plant at the headworks, a system that pumps it through a series of fine screens to remove debris and grit. There are two headworks, a smaller one for the winter and a larger one for the summer.

Sewage next continues to primary clarifiers where heavy sludge and debris settles to the bottom of the tanks, and then it continues to the oxidation towers. From there, the wastewater continues to the exterior aeration basins where bacteria digest and break down organic matter, and then it is From there, sent to the Fine Clarifier 2, where particles are allowed to settle out of the water, again. Water at the top of the tank is skimmed off and sent to the chlorine contact tank for disinfection.


Gesturing toward a clarifier that is only used during the summer months, Manager Jay Davis explains how wastewater is treated Friday, January 26. Gesturing toward a clarifier that is only used during the summer months, Manager Jay Davis explains how wastewater is treated Friday, January 26. “We’re making clean water,” Mr. Davis said of the process and, at this point, the water is cleaned and can be sent back to Lake Huron.

Throughout the wastewater treatment process, solid material is diverted for disinfecting, the water is pressed out of it, and the resulting sludge is pumped into a wagon and transported to the Solid Waste Handling Facility, from where it is shipped to the landfill in Dafter.

If the screw press were to be upgraded to include a steam sterilization unit, the sludge could be composted at the Solid Waste Handling Facility rather than shipped off, but that equipment is expensive, Mr. Davis said.

During the height of the season, June, July, and August, 15,000 to 20,000 gallons of the so-called biosolids will be processed at the screw press each day.

“That’s something you don’t want to get behind on,” Mr. Davis said. “It’s better to stay ahead.”

During the winter, the plant stockpiles the sludge in a 49,000 gallon tank until the screw press begins operating in the spring. The department’s “honey wagon,” a red device towed behind a tractor that is used to pump septic tanks in an emergency, is also stored in the screw press building during the winter.

Back in the basement of the wastewater treatment plant is the intricate network of pipes and pumps responsible for sending the solids and filtrate to various parts of the facility. Pumps and blowers also send oxygen to the exterior tanks where bacteria digest the waste.

Near the stairs, a small pipe extends above a sink to allow plant operators to collect samples of the sanitized water, also called final effluent, for testing.

The effluent looks clear when Mr. Davis holds a beaker of it up to the light.

“It’s disinfected and on its way back to the lake,” he announces. “That’s why we’re here.”

The effluent must be tested five days a week for oxygen, total suspended solids, phosphorus, fecal coliform bacteria, chlorine, and pH. It is tested for mercury four times a year.

Testing for phosphorus takes four to five hours, and if something goes wrong along the way, the whole process must be restarted. During the various stages of chemical tests, the effluent goes through a range of colors, from clear to pink to gold to blue. The blue is analyzed by a photospectrometer to determine how much phosphorus is in the water. The darker the blue, Mr. Gallagher said, the more phosphorus there is, so he wants the cleansed wastewater to be as pale as possible. The standard for phosphorus is one part per million (ppm) of phosphorus in the final effluent, but the plant typically produces 0.25 ppm or less.

The two plant operators like to engage in a friendly competition to see whose samples are lower.

Near the entrance of the chemistry laboratory is a control panel installed during the 2013 upgrade, next to a wall of electrical buckets built in the 1970s. A circular graph tracing the flow rates into the plant spins on the door of the control panel, and a green pen squiggles back and forth, tracking flow. The chart has to be changed every day at 10 a.m.

The amount of wastewater treated at the plant fluctuates greatly throughout the year. Flows this winter have increased because residents and businesses must keep a steady stream of water running to prevent pipes freezing.

On a typical winter day, the plant processes about 70,000 gallons of wastewater. During May, that increases to 200,000 to 300,000 gallons a day. In July and August, the plant receives between 800,000 and 900,000 of sewage a day. The plant’s flow can also increase significantly during large rain events, as close to 100,000 gallons of precipitation can be sent to the plant. If such large influxes of water occur in the spring, wastewater can be diverted to the summer operating tanks to be treated at a later time.

Because the plant processes much less wastewater in the winter, portions of the plant are shut down and winterized.

Activity at the wastewater plant will surge in the spring, and the crew has to get its facilities online quickly. Spring can be challenging, especially when seasonal employees return to the Island in droves, increasing usage as the rest of the plant, including three more clarifying tanks, is just coming back into use.

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