In a $1.9 million purchase, the Grand Strand Water & Sewer Authority recently upgraded and expanded two wastewater treatment plants in the Grand Strand area of South Carolina with USFilter triple ditch oxidation systems.
Initiated to comply with reduced state discharge limit levels, the new systems will remove ammonia to 0.7 mg/L year-round.
The GSWSA selected the triple ditch system for its ability to comply with the new ammonia limit and to cost-effectively address sensitive water concerns at both plants. At the North Strand Regional Water Plant in Longs, S.C., there was a seasonal flow change that created problems in operations.
"The North Strand plant services a residential area as well as the beach community of North Myrtle Beach," said Larry Schwartz, environmental system coordinator for the Grand Strand Water & Sewer Authority. "We needed a system that had the ability to adapt to changing flows and adjust energy requirements to achieve that."
The area around the County Wastewater Treatment Plant in Conway, S.C., required the usage of pilings under all structures.
"The small footprint minimized the number of piles required, which greatly reduced the total construction cost. It also allowed us to retrofit the new plant on an existing site, located inside the old lagoon, which was convenient," said Schwartz.
The triple ditch system offers the simplicity of an oxidation ditch system, and the functionality of an SBR, without the associated intermittent surging discharge and fluctuating water level associated with SBR’s. The triple ditch’s large surface area and alternating series flow pattern produce consistently high effluent quality with a continuous discharge and constant water level.
The Conway plant began operation at the end of May while the North Strand plan is scheduled to begin start-up in early September.