The following is part one of The Voice’s two-part series on upgrades to Ithaca’s water treatment facilities. Part two, which will run Sunday, will feature the Ithaca Area Waste Water Treatment Plant.
Ithaca, N.Y. — In January 1903 an outbreak of typhoid struck Ithaca and killed 83 Ithacans, including 23 Cornell students. One of every ten city residents fell ill.
By August of that year, and after securing a $150,000 grant from Cornell, the Ithaca Water Company had built a new water plant, which used a “rapid” or “mechanical” purification process to ensure that bacteria from contaminated Six-Mile Creek would not reach the mouths of city residents.
That plant is the same plant that currently supplies the city of Ithaca with its water – between 3 and 3.4 million gallons per day. It is now being torn down and replaced as part of major renovations to Ithaca’s water supply infrastructure.
The new plant, which will be built in the old plant’s location on Water Street, will feature new filtration technology, new settling basins, and an “interconnect building” with valves and meters for when the plant needs to borrow water from other plants. Renovations are also being made to auxiliary parts of the water system including the plant’s reservoir intake structure and its Giles Street sludge press building.
According to Cynthia Brock, councilmember for Ithaca’s first ward, the city has been discussing improving the city’s water infrastructure for at least the past twenty years.
When faced with the options of upgrading the existing plant and replacing it, the city decided it would be better to build a new, state of the art plant which will be equipped to deal with new contaminants, according to Brock.
“The new filtration system will ensure that whatever contaminants might enter into watershed will be filtered out,” Brock said.
Common Council has authorized $36.7 million dollars for the project. Common Council member Seph Murtagh and City Controller Stephen Thayer both say that they believe the project is the most expensive in city history.
The project is currently underway and is expected to be completed in September of 2016. Mayor Svante Myrick has said that water bills across the city will double as a result of the new plant, according to The Ithaca Times.
This story provides details about the technical operations of the proposed plant.
Jump to which part of the new water treatment process you want to learn about:
1. Intake Treatment
2. Chemical Application Chambers, Settling
3. Membrane Filtration
5. Sludge Press
The push to replace the water treatment plant is due in part to concerns about the danger of “disinfection byproducts” – dangerous chemicals which result from chlorine’s interaction with organic material in water. Water and sewer officials agree that the current method of treatment and filtration is not optimized to deal with these dangerous byproducts, which have been linked to cancer.
“Some of the long-term disinfection byproducts are carcinogenic and toxic,” said Erik Whitney, P.E., assistant superintendent the Department of Public Works, “they’re thinking some of the bladder cancers of people in their 80s are probably related to them.”
Whitney said that the latest Clean Water Act emphasized the importance of removing these contaminants from drinking water.
Chuck Baker, the plant’s chief operator, said that the new plant’s treatment process will be better at handling these chemicals.
By treating raw water with an oxidizer (sodium permanganate) at the intake structure, and by allowing the water to mix with this oxidizer as it travels through roughly 10,000 ft of pipe on its way to the water plant, there will be less organic material in the water by the time it gets to the plant for treatment.
Treat, Churn, Settle
Once the water reaches the plant, the water is treated again – this time with chlorine dioxide – and then mixed in chemical application chambers.
“The idea is to get the water and the chemicals as much contact as possible,” Baker said.
As with the old process, the purpose of this step is to create a coagulated dirt-chemical “floc” (suspended milky specks) which are heavy and are thus able to settle out in large basins.
Renovations will include new mixing chambers, new flocculation chambers — where chemicals are mixed in with the untreated water — as well as new settling basins.
Membranes: An absolute barrier
Once the “floc” has settled out of the water, the water is treated with chlorine and then goes on to the filtering stage. In the new plant, high-tech membrane filtering technology will replace the anthracite (coal) and sand filtering process that has been used for the past century.
In the old process, water would percolate through the sand and coal filters, and would leave bacteria and residue “floc” behind. The filters would then have to be manually rinsed in a multi-step “backwashing phase.”
In the new process, water will be filtered through microscopic pores on the outside of membranous, noodle-like filaments. Water that makes it through the pores will travel up the noodle and out onto the next stage of treatment.
Particulate matter – bacteria, viruses, etc. – which doesn’t make it through the pores will be rinsed off and discarded when the membrane system cleans itself. This self-cleaning process will happen 3-4 times an hour.
“We used to have certain bacteria and viruses which would get through the filters,” Whitney said. “We relied on chlorine to minimize that problem. But membranes won’t let those things through in the first place.”
Baker said the plant will continue to still chlorinate the water after it is filtered. Baker said that the the variety and volume of chemicals is expected to increase in the future plant.
“We like redudancy,” Baker said. “We like to be confident about the product we’re putting out.”
At full capacity, with 250 membrane modules filtering simultaneously, the plant will be able to filter about five million gallons of water per day.
The new plant will also have a new sludge basin and press facility on Giles Street to replace the lagoons which were previously used to settle the plant’s refuse. Excess water will be routed down to Six Mile Creek and the pressed sludge – which is mainly just dried clay – will be put to use.
Because the plant has a”beneficial use” designation for its sludge, it is allowed to mix it with compost (one part sludge, nine parts compost) and use it on land within city limits.
“Our sludge alone can grow beans real well,” Baker said.
Images of the Future Plant: