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System was installed in one of two ponds comprising middle "train" at city's treatment facility
The City of Jacksonville, N.C., announced that it has completed installation of a wastewater treatment system in a pilot project that is expected to eliminate built-up organic sludge.
The Blue Frog System by Absolute Aeration LLC was installed on June 6 and 7 in one of two ponds that comprise the middle “train” at the city’s wastewater treatment facility. The technology is expected to digest the built-up sludge in situ, thereby eliminating the need to mechanically dredge the waste.
Currently, the city of Jacksonville (est. pop. 82,000) treats up to 6.5 million gal of wastewater daily, with the residual effluent applied to roughly 7,400 acres of cultivated forestland on the site. Every three to five years, each of the treatment lagoons must be mechanically dredged, at a cost of more than $80,000 per pond (or $500,000 for the entire facility), with thousands of pounds of Class A solids applied to the adjacent cropland following strict permitting requirements governed by the state.
“The process of draining the ponds, dredging them and manually removing the sludge is very time-consuming and expensive,” said Pete Deaver, utility services superintendent for the city of Jacksonville. “It has to be done during the pre-crop planting season in order to secure a state permit, and the process has to be repeated on a regular basis. In addition, during the dredging process, we have to take the lagoons offline, which presents additional challenges.”
In February, Deaver was approached by Steve Pagley of Consolidated Pipe & Supply Co., a licensed broker and distributor representing Absolute Aeration in North Carolina. Pagley explained the benefits of the Blue Frog System and, later, introduced representatives of the city to their counterparts at two sites in Georgia that have already documented positive results with the technology.
“In our world, there’s a tendency to not want to try new approaches; but word travels fast when something new comes along that really works,” Deaver said. “Operators will always shoot straight with fellow operators, so they’ll tell you if something works, and they’ll tell you if it doesn’t. The folks in Georgia told us in no uncertain terms that the Blue Frogs did exactly what they were designed to do.”
The Jacksonville treatment facility consists of three aerated trains, with two wastewater ponds in each train. The ponds are large-flow, deep lagoons that feed into an extensive variable-depth, three-pond surge system. The treatment lagoons cover 10 acres of land and have a capacity of 40 million gal. Storage lagoons cover an additional 90 acres of land and have a capacity of 720 million gal when full. More than 21,000 sprinklers spray roughly 6.5 million gal of effluent over the adjacent cropland per day. The storage lagoons hold the wastewater during periods of inclement weather, when spray irrigation is not feasible.
Prior to the land-application practice, the city discharged its treated wastewater into Wilson Bay from an outdated and overwhelmed plant. City officials worked 12 years to build an environmentally friendly and expandable treatment system that did not discharge into the New River. It was the first large-scale plant in North Carolina.
“We are always looking for more cost-effective and environmentally responsible ways to do our jobs here in Jacksonville, so when we heard about the Blue Frog System, we were immediately interested,” continued Deaver. “We chose our middle train for the pilot project; and assuming we achieve the expected results, we plan to expand the Blue Frog installation to our other lagoons around this time next year. Eventually, we hope to eliminate the need for mechanical dredging and land application completely.”
The Absolute Aeration team installed 14 Blue Frog circulators in the second cell of the middle train over a two-day period. The technology employs “biodredging”, which uses natural biological processes to enhance organic sludge digestion. The circulators move water horizontally to create radial outflowing currents within the lagoon, each moving up to seven million gallons of wastewater per day. The biologial system targets sludge-digesting bacteria in the lagoon that form synergistic anaerobic biofilms in tight, mineral-based granules. These biofilms spread out to create a granular sludge bed reactor (GSBR) over the entire bottom. Surface biosolids are delivered to the GSBR, liquefied, and turned into gas by the bacteria immobilized in and on the granule. The gas rises and gently mixes the water column, continuously feeding the granules to increase their productivity.
Over the coming weeks and months, those microbes will “eat” the organic waste that has been stored up while digesting incoming organic solids before they have a chance to settle. No chemicals or outside microbes are ever introduced to the lagoon.
The Blue Frog units operate using 3 hp aeration motors, thereby consuming substantially less energy than the 10 hp and 50 hp units currently operating at the Jacksonville facility. The city expects to achieve significant savings in its $700,000 annual electricity bill as another positive byproduct of the new system.
Blue Frog President Grace Corbino explained that the Jacksonville installation is best described as a partial Blue Frog system designed to reduce organic solids, primarily in the middle train. She projected that the built-up sludge in the test pond will be reduced by about 25% in the first 12 months of operation. Within the first 24 months, roughly 1 to 2 ft of granules will remain. This, in turn, will return another 9 to 10 million gal of capacity to the system.
“The City of Jacksonville has a well-earned reputation for testing innovative approaches and being responsible stewards of the environment and their rate payers’ money,” said Corbino. “Jacksonville is the first municipal wastewater facility in North Carolina to test our system, but once we demonstrate our results, we expect many more cities to invite us in.”