Aging sewer plant not up to task
If the Fairfield City Council approves all the proposed repairs to the city’s sewer system, the first order of business will be to fix the headworks at the sewer treatment plant.
Wastewater plant superintendent Shawn Worley and operations supervisor Scott Connelly said the headworks is causing the plant employees headaches by failing to do its job.
The headworks is the first step in a four step process of treating the sewage. The headworks separates the organic matter in the sewer from the inorganic matter, which cannot decompose easily.
Worley and Connelly said the headworks structure is too old and inefficient and it lets too much inorganic matter slip through the cracks. This causes problems down the line by forcing the plant to use greater energy to treat the waste.
The headworks filters the inorganic matter by allowing the sewage to flow into a screen which catches the large objects. Connelly is tasked with raking the objects off the screen and tossing them into a dumpster.
The screen, which has openings 1.5 inches wide, is much coarser than most modern screens and allows many inorganic objects to pass. The headworks station Worley and Connelly want to replace it with would have screens with openings 0.25 inches wide.
Most of the inorganic objects that pass through the screen are caught during the second phase of process which is grit removal. The sewage flow is slowed to 1 foot per second by narrowing the channel through which it passes. The sand and other hard matter that sink to the bottom during this process are scooped up by a machine.
Connelly operates the grit remover manually and sees what objects it uncovers from the bottom of the sewage. He has recovered many toys through this process, which he keeps at the facility as souvenirs.
Worley said these and other inorganic materials are the biggest problem the headworks station faces. He said the objects that most commonly clog the screens and the pipes are feminine hygiene products, paper towels, prophylactics and other fibrous materials. He said even wipes that are advertised as “flushable” should not be flushed since they cause problems for the plant, too.
Once the sand is separated from the rest of the sewage, an endloader scoops it up, puts it in the dumpster and takes it to a landfill.
Connelly said 99 percent of the hard, inorganic material filtered out through the first two steps should never be in the sewer in the first place. He said garbage disposals are responsible for bringing a great deal of material to the sewer plant that should not be put down the drain.
Worley said composting organic waste is ideal and asked the city’s residents to compost whenever possible instead of sending material down the garbage disposal. Connelly said he frequently sees corn and eggshells in the sewage, which he said should either be composted or put in the trash.
The sewer plant also has problems processing oil and grease, which are sometimes poured down kitchen drains but which Worley said should not be.
Worley said Fairfield’s residents have a good sense for what can be put down the drain and what cannot, but there is still room for improvement. He said if the inorganic materials could be removed from the sewage, the city wouldn’t have to spend so much energy on treating the waste.
Once the inorganic matter and the sand are removed, air is pumped into the sewage to allow bacteria to thrive. The bacteria eat the sewage, which breaks it down. If a lot of inorganic matter reaches the treatment stage, more air must be pumped into the sewage before it decomposes. This equates to more electricity and more wear and tear on the equipment.
The headworks was built in the 1960s. The equipment inside had a life expectancy of 20-25 years, but it’s still being used. Worley said all of the equipment in the headworks will either be repaired or replaced at the conclusion of the sewer project the city is undertaking.
Worley said the revamped headworks facility will rely more on machines to separate the inorganic matter rather than on a worker who has to physically rake the screens clean. It will also operate around the clock, after the employees have gone home for the day.
The new treatment system will disinfect the sewage by exposing it to high intensity UV light, which alters the bacteria so they cannot reproduce.
Worley hopes to begin replacing the equipment next spring and to have it done by 2016..