Chelsea water customers can look forward to a possible 50 percent reduction in water hardness by July 1.

Currently, water pumped through municipal pipelines has a mineral hardness of approximately 400 parts per million.

The Chelsea Water Treatment Plant’s reverse osmosis water softening system was taken off line April 19 because of problems ranging from rapidly clogging filters to pinhole leaks in the filtration pipes.

The bypass took place in anticipation of increased water demand during the summer.

To fix the plant’s reverse osmosis system, manufacturer GE Osmonics will replace stainless steel pipeline housings within the plant’s two reverse osmosis skids with Fiberglas housings.

Cleaning chemicals for the reverse osmosis pipes will be changed from hydrochloric acid to a citric acid-based chemical.

Chelsea City Manager Mike Steklac said Monday the city is working on a five-year agreement with GE Osmonics to maintain the reverse osmosis system.

Under the agreement, GE Osmonics would be responsible for ensuring problems encountered at the plant in the past won’t occur again in the future, Steklac said.

The plant’s Tonka iron removal system is being studied to change a feed point for a chemical used to remove iron from the water.

A GE Osmonics troubleshooting study found a malfunction with the iron removal process, which allowed suspended material into the reverse-osmosis system fed on by bacteria.

The combination of bacteria and corrosion was the cause of the pinhole leaks, GE Osmonics reported.

The five-year agreement with GE Osmonics would cost the city between $12,000 and $14,000 per month. It would include membrane and cartridge filter maintenance, as well as cleaning chemicals and labor in addition to the new housings.

Steklac said such payments could be covered by the Chelsea Water Department’s budget, which would otherwise be freed from expenditures for new cleaning chemicals and filters.

If GE Osmonics is able to improve the operation of the reverse osmosis system, reduce the frequency of cleanings, and reduce frequency of replacing cartridge filters and reverse osmosis membranes, the agreement has a review clause that could reduce the monthly cost to the city, Steklac said.

Conversely, he said if the water softening system’s operational cost rise — for reasons such as increased cleanings and frequent replacement of cartridge filters — the monthly cost of the agreement could reach a "not-to-exceed" cap.

City personnel will meet this week to discuss terms of the agreement.

The city is aiming to have one of the plant’s two reverse osmosis skids functional by July 1. At that time, water hardness could be brought down to about 200 parts per million, Steklac said.

Although production of water permeate through the skid is expected to stay relatively constant, the actual water hardness attained in that scenario could vary, depending on how much water must be bypassed from softening in order to supply water pressures that meet customer demands.

Steklac said once the reverse osmosis skid is brought on line, he plans to make new water hardness data available to the public.

Another change at the plant will entail installation of variable frequency drive pumps that would allow water pressure fed into the softening system to be brought up gradually.

A large pipe on the cleaning system fractured as the result of a "water hammer" effect, which Steklac said would be mitigated by the new pumps.

To diagnose what went wrong in the plant, water samples will be taken to measure microbial activity that could have caused corrosion.

"Autopsies" of the fouled membranes removed from the plant will be performed to determine why they became sullied so quickly.

In addition, iron filter backwash lagoons will be cleaned out to increase capacity.

The Michigan Department of Environmental Quality is involved with the plant discussions, and will advise if any changes made at the plant will require a formal review, Steklac said.

When Reverse Osmosis Unit 2 becomes operational this summer, GE Osmonics and city engineers will monitor its performance. Concurrently, housings and membranes will be replaced on Reverse Osmosis Unit 1.

When engineers determine that Reverse Osmosis Unit 2 is working properly, Reverse Osmosis Unit 1 will become operational, Steklac said.

At that time, Unit 2 will either continue to operate, or will be taken off line to replace its housings if they begin to leak. While Unit 2 does not have pinhole leaks, metal pitting has been found on the unit.

With the water softeners bypassed, customers may notice hard water stains or buildup on household items. Soaps and detergents will lose some effectiveness during bathing, dishwashing, or in the laundry.

Another side effect of harder water could be lower flows through showerheads and pipes caused by calcium buildups.

Replacement of the plant’s reverse osmosis membranes would cost about $118,000. Installation of the variable frequency drive pumps would cost $35,000.

Steklac said municipal water fees might be raised to cover those costs. Because of the city’s obligation to pay off water system bonds, customers will not receive rebates or water bill discounts, Steklac said.