Innovation makes it possible for communities to retain wastewater-treatment facilities
Crosby Construction of Fort Wayne is at the forefront of an innovation that enables smaller municipalities to retain their lower-maintenance and lower-cost lagoon-style wastewater-treatment facilities while meeting increasingly stringent quality standards for treated wastewater discharged back into watersheds.
Crosby recently completed the work necessary to create a Submerged Attached Growth Reactor (SAGR) wastewater-treatment plant for the City of Berne and has also completed the same type of project for Mentone and Kennard. The three Crosby-led SAGR wastewater-treatment projects are the only ones of their kind in Indiana.
“Although we’re a full-service construction company providing a complete range of services, wastewater treatment is one of our specialties,” says Crosby Construction Vice President Michael Mattingly. “Over the years, we’ve been engaged in improving existing wastewater treatment facilities or constructing new facilities. Most of those projects involved mechanical wastewater-treatment plants. The SAGR process, however, is a more affordable alternative to communities looking for wastewater-treatment solutions, and we’ve been fortunate to have the opportunity to work on the only three SAGR systems created in the state thus far.”
The SAGR process was developed by Nelson Environmental of Winnipeg, Canada. The goal is to allow smaller communities to keep their lagoon-cell treatment facilities and be in compliance with quality standards for treated wastewater before it’s discharged into watersheds such as rivers and streams. If forced to abandon their existing lagoon-cell systems, these communities would be required to build new mechanical facilities. The cost of construction and maintenance of these new mechanical facilities would be prohibitive for many communities.
The biggest problem with lagoon-cell wastewater-treatment facilities is that they weren’t designed to meet the Environmental Protection Agency’s increasingly stringent standards for ammonia removal. As a result, these lagoon systems need to be upgraded.
Although it occurs naturally and is essential to life in many ways, ammonia in levels beyond EPA standards can be detrimental to the environment. The most common way to remove excess ammonia in wastewater lagoons is through nitrification, a biological process that incorporates oxygen by means of aeration. Removal is achieved when the oxygen works with the bacteria already in the wastewater to break down the ammonia, which is then released into the atmosphere as nitrogen gas.
To upgrade the three lagoon wastewater treatment facilities in Indiana with the SAGR technology, Crosby installed aerated gravel beds with horizontal flow distribution chambers that distribute influent wastewater across the width of each cell. On-site blowers feed the submerged aeration systems, and since the blowers are the only mechanical component for this system, adjustments and maintenance for the treatment process is minimal. An effluent collection chamber at the back end of the lagoon collects all the treated effluent and channels it to the discharge structure. There is no solids return to monitor and adjust and no sludge to dispose of. In addition, the key breakthrough with this technology is that it’s effective in ammonia removal even when temperatures drop during the winter.
The cost to create SAGR-based treatment facilities depends on the size and number of lagoon cells a community operates. For example, Berne operates four 70-by-262-feet lagoons, and the city’s SAGR project had a price tag of $6.7 million. With two 25-by-200-feet cells, Kennard’s system cost $1.6 million. Mentone’s two lagoons each measured 40 by 110 feet, and the project was completed for $700,000. The size of the lagoons is dependent upon the desired capacity for wastewater treatment.
“Building new mechanical wastewater-treatment facilities usually costs much more, so the SAGR system is a very cost-effective solution,” says Crosby Construction Project Manager Jason Clear. “In addition, the operation of mechanical facilities is also costly. The SAGR system requires minimal day-to-day maintenance and an estimated energy savings of 50 percent. Less initial cost combined with low maintenance costs is the perfect solution for many communities whose lagoon systems need upgrades to meet EPA standards.”