Water Plants That Feed Sodium Permaganate
Interested in Treatment?
Get Treatment articles, news and videos right in your inbox! Sign up now.
Treatment + Get Alerts
When the 25-year-old filters at the Jackson Mills Road water treatment plant began to fail, the Township of Freehold water utility decided to upgrade the filter media as well as the filter system.
By switching to manganese greensand plus filter media, the utility saves $10,000 in energy costs and $15,000 in chemical costs annually, while doubling the flow-through rate.
Freehold is a New Jersey bedroom community for New York City. The water utility has 11,600 service customers and an annual operation budget of $600,000. About $500,000 is invested back into the system through capital improvements, such as the filter rehabilitation project.
The township has 10 wells with capacities from 500 to 1,200 gpm and buys surface water (up to 880,000 gpd) from United Water. The utility combines and treats the water at three plants that total 8.14 mgd capacity. Five team members handle operations and maintenance of the plants and pipeline. All operators have T-1 to T-3 water treatment licenses.
Filter checks
The utility's Jackson Mills Road plant, built in 1985, uses oxidation reduction treatment and is automated with a SCADA system. Lime is used for pH control and chlorine oxidation. Previously, the plant used four multimedia pressure filters with manganese greensand, anthracite and garnet as filter media for iron and manganese removal. Potassium permanganate was used to recharge the greensand continuously. Each filter processed about 250,000 gallons before backwash.
The water utility annually inspected the filter vessel, and a lab checked the media for effective grain size. "The existing filter media was 25 years old and in good condition with grain hardness, effective size and uniformed coefficient near that of new material," says Bob Koches, superintendent of public utilities. "This is a true representation of how well the operators take care of the plant."
However, in 2010, operators noticed some mounding of the media in a filter and possible drain problems during the air-wash cycle. The mounding indicated a break in the air line because the air was not coming up through the entire filter evenly. Realizing that the filter system had reached its useful life, the Freehold team decided to undertake total plant filter rehabilitation.
All four filters were vacuumed or shoveled by hand to remove media, and all internal filter parts were removed. A new air-wash system, sand strainers and influent/effluent lines were installed. The project cost $250,000, paid with capital fund savings and a 30-year loan from the township.
New filter media
Instead of returning to manganese greensand, the utility upgraded to manganese greensand plus because it is harder and more durable and requires fewer chemicals. "Manganese greensand is very soft and easily crushed, so we had to add sodium aluminate to harden it up," Koches says.
"Manganese greensand plus has a manganese oxide coating and is extremely hard, so we don't have to worry about the water pressures put on it. Also, the old filter media used potassium permanganate as a recharging agent. Now we just use sodium hypochlorite for recharging — it is cheaper and already being used for disinfecting. We've eliminated the need for potassium permanganate and sodium aluminate. The reduction in chemicals saves $15,000 annually, and there is less labor for maintaining the chemical feed systems.
"Potassium permanganate is time-consuming in its maintenance," Koches says. "It turns everything a purple-brown color and takes up a lot of surface area. We were mixing batches in a large tank. The chemical feed systems required daily readings and inspections because they ran constantly. Now we've eliminated those chemical feed systems and related maintenance."
With the improved hardness of manganese greensand plus, the plant has increased flow-through between backwashes, saving up to $10,000 in energy because the backwash pumps run only half as often. "We are no longer concerned with head pressures on the filters because we don't worry about crushing the harder greensand plus," Koches says.
"This allows for quite a bit more flow-through and loading on the filters, so we've doubled our capacity to 500,000 gallons between filter backwashes and reduced the related energy-consumption and water-wasting. In addition, fewer backwashes mean the plant is discharging less water into the sanitary sewer system, which is environmentally important."
Operator care
Operators were involved in every step of filter rehabilitation. They worked closely with contractors during the changeover and learned about the new system and its capabilities. "Our operators are really special," Koches says. "We've created an atmosphere of letting them do the things they need to do on their own because they know the operation and maintenance best. They enjoy making decisions on their own, and they take the water plant home with them every night. Our operators are just extremely into their jobs."
Source: https://www.tpomag.com/editorial/2014/03/free_flowing_wso
Post a Comment for "Water Plants That Feed Sodium Permaganate"