In order to keep in compliance with the Utah Pollutant Discharge Elimination System permit, the Moab City Council approved the purchase of a dewatering belt press.
The Moab City Waste Water Treatment Plant (WWTP) is more than 50 years old. The WWTP, which is responsible for the treatment and disposal of waste water from businesses and homes in the Moab valley, has not been upgraded since 1996. The life expectancy for a similar sewer system is around 40 years.
“The equipment and plumbing at the plant are subjected to much greater corrosive stresses than any other plumbing and equipment within the City,” said Jeff Foster, the Moab City Public Works director.
Moab City officials and the City Council have been working on plans to upgrade or rebuild the WWTP, although any type of construction is still three to four years away. Council member Kyle Bailey said with regulation changes that will be implemented in the future, a new plant will be necessary.
“The Grand Water and Sewer Service Agency also uses the plant and we’ve been informed by state government, the Environmental Protection Agency, and other agencies that they have redone some of their regulation on the fluids we can release into the Colorado River,” he said. “They are upping their standards so we are going to have to redo the plant soon.”
Bailey said the city is working with engineering firms in planining for the new facility, but no cost estimates have been released yet.
“It’s going to be expensive,” he said. “We are trying to save as much of the existing plant as possible.”
Moab residents and businesses saw an increase in their sewer rate of 10 percent in July, and part of this increase is to help cover the anticipated increase in costs for a new WWTP. The city also imposed a 5-percent increase to sewer rates in 2013. There are likely to be more increases over the next couple of years.
“This press will keep the WWTP running cleaner and more efficiently until a plant upgrade has been designed and installed,” Foster said.
During processing at the WWTP, waste water is treated and processed into a sludge. This sludge is dried out at the plant and then transported to the Moab landfill. With the increase in use of the facility, the beds used for drying the sludge have been overfilled and the sludge is no longer drying out as quickly. Weather conditions, including periods of higher precipitation and colder temperatures during the past couple years, have also decreased the effectiveness of the solar drying system the plant currently uses.
“This problem was causing the WWTP to recirculate high-strength water back through the plant when it should have been going to the drying beds, and therefore, the WWTP started violating the permit the city has with the Utah Department of Environmental Quality, Division of Drinking Water,” Foster said.
Foster said the permit requires the city to keep a number of contaminants under control, but the two the WWTP were struggling with were the Total Suspended Solids (TSS) and Biochemical Oxygenated Demand (BOD).
Steve Onysko, an employee with the Utah Division of Drinking Water, said when solids, such as fecal matter or food waste, enter a WWTP, they use oxygen to grow into bacteria. If the solids are not dissolved enough during the processing time, contaminants can be passed out of the plant with the treated waste water into the rivers and other local waterways.
“This can be bad for the river because the contaminant will pull oxygen out of the water in order to grow the bacteria,” he said. “So, when the contaminant hits the water, it can kill fish and make less freshwater available. It is also bad for recreation water and possibly drinking water for downstream users.”
The City of Moab rented a dewatering press to decrease the amount of time it takes for the sludge to dry while at the WWTP.
“The dewatering press, in essence, squeezes water out of the sludge so that it can be transported without any additional drying required,” Foster said. “By doing so, the plant runs cleaner and more efficiently with less high-concentrate water recirculating through the plant.”
In April 2014, the city started renting a refurbished dewatering press from MSD Environmental Services. The WWTP immediately started running the press two days a week, and when regulators revisited the facility in June, they noted only minimal concerns with the contaminant levels.
Rental fees for the press were $12,500 per month. The city voted to approve purchasing the machine for $219,375 instead of continuing to pay the rental fee.
The equipment does have some disadvantages, Foster said.
“The press has additional costs attached, it takes time for the operators to run it, it uses additional power and water to process the sludge,” he said. “In order to meet the requirements of the permit, the press is a necessity at this point until the plant can be upgraded.”
Machine helps GWSSA conform to regulations, buys time for necessary plant upgrades
“This press will keep the WWTP running cleaner and more efficiently until a plant upgrade has been designed and installed.”