Transforming wastewater into something useful

WRITTEN BY: Michael Grimaldi

KC Water’s Blue River Wastewater Treatment Plant is poised to move from aging infrastructure based on 19th-century technology to 21st-century technology with plans to implement an evolutionary new process.

The treatment plant uses 1960s-era incinerators to dispose of material collected from wastewater. Design work is underway to enable KC Water to transform waste into fertilizer clean enough to be used in farm fields and gardens; and into gas that can be used as fuel for industrial heating equipment or even to heat homes and businesses or to run vehicles.

By replacing decades-old infrastructure with new technology, KC Water also can help keep the air cleaner and reduce odors in the area.

“Actual final uses for the byproducts of the new process will be determined in the future,” said Terry Leeds, KC Water Director. “The real breakthrough today is that instead of throwing away incinerated wastewater solids, we will be making useful products.”

From raw sewage to productive reuse | Thermal hydrolysis process (THP) represents a major evolution in the way the City will handle wastewater from homes and businesses.

In times long past, raw sewage was simply drained to rivers and streams to get it away from people as quickly as possible. Clearly, that wasn’t good for the environment. Population growth and better scientific understanding proved that the old ways were not appropriate.

The present approach calls for removing solid waste from the wastewater stream. The separated water is treated before returning it cleanly to the river. The separated solids are incinerated.

It’s an imperfect system. The incinerator ash needs to be disposed of, and there is only so much space in landfills. Incineration requires complicated air-quality control equipment that utilizes chemicals and large amounts of clean water to minimize air pollution.

Technological evolution | THP changes everything. The Blue River Wastewater Treatment Plant will evolve primarily from a waste disposal facility to a resource recovery facility.

THP is a two-step process:

  • Solids separated from wastewater in settling tanks are pressure-cooked to about 165 degrees Celsius, sterilizing the biosolids.
  • The resulting product is mixed with bacteria in a process known as anaerobic digestion. Essentially, bugs “eat” the stuff from the first step and create two clean, usable products: biogas and biosolids. KC Water uses anaerobic digestion to treat a portion of solids, but the digesters are not large enough to treat all solids.

Communities and businesses nationwide use biogas to produce mechanical power, fuel boilers and furnaces, run alternative-fuel vehicles, or heat homes or businesses.

A variety of steps are necessary for THP, including sludge screening, sludge degritting, pre- and final dewatering, intermediate sludge storage, and heat exchangers. The process will produce more ammonia that will be removed in a sidestream treatment process to maintain Missouri River water quality.

Managing for efficiency | Another factor that led KC Water to THP is a lack of expansion space at the Blue River Wastewater Treatment Plant site. With THP in the mix, the plant’s anaerobic digester capacity will double without constructing additional anaerobic digesters at the site. This increase will allow outdated incinerators to be shut down and demolished.

THP gives KC Water the ability to recover phosphorus in the future. The project will better prepare KC Water for any future rules and regulations necessary to protect human health and the environment.

Solids from other wastewater treatment plants also are processed at the Blue River plant and will be treated by THP in the future.

Following the recommendations of a 2017 Cost of Service Task Force, KC Water is pursuing state and federal funding through the Water Infrastructure Finance and Innovation Act. These outside funding sources typically offer favorable borrowing rates and minimize the impact of the THP project on KC Water customer bills.

In the long run, we all win. THP is a better way to handle wastewater for KC Water workers, customers, and the environment.

Above: The Biosolids handling (outlined in red) at the Blue River Wastewater Treatment Plant near I-435 and Front Street in the East Bottoms will be upgraded in a project getting underway this fall. Plans are to double the capacity of existing digesters and shut down antiquated incinerators. New thermal hydrolysis process (THP) equipment, similar to that installed by DC Water in Washington, D.C., will increase treatment plant capacity and enable KC Water to put solids removed from wastewater to productive use.