City of Cave Springs
Tucked away in the northwest corner of Arkansas, the headquarters of three corporate giants are within 20 miles of one another: Wal-Mart in Bentonville, Tyson Foods in Springdale and JB Hunt in Lowell. Spurred by Wal_Mart's rise and the continued success of the other two, this region has become one of the fastest growing residential areas in the United States.
Because it is minutes from the Northwest Arkansas Regional Airport and within easy commuting distance to all of those cities, Caave Springs became the next small town to develop.
The plan included 1495 new homes, a golf course, a downtown and a secondary commercial area. The total area was about 1000 acres and would be divided into 10 separate subdivisions.
Each developer was dealing with a multi-million dollar project and had a lot at stake. But, once they understood that we would get a better treatment system, have the opportunity to offer the city an
asset AND save money, they realized this would be a win-win-win scenario.
Beyond the initial hurdle of getting all the developers and city to agree to the plan, the actual implementation of the system was not difficult at all. At full build out, they system will handle 412,000 gallons per day (gdp). Initially, however, only a small number of homes would be contribution wastewater to the system. "low flow rates can be problematic for some treatment technologies. this system haad to be versatile enough to handle extreme fluctuations and still be easy to maintain and cost effective to operate."
Typically, the disposal method for treating this volume of wastewater would result in a surface water discharge either into a lake, stream or ocean. Because of the sensitive environmental issues with endagered species, such as blind cave fish, the city really wanted to dischage underground
There are several environmental advantages to using sub-surface drip irrigation:
It provides additional treatment and natural filtration
It captures water for irrigation
It avoids sending wastewater downstream
It protects wildlife
One of the key challenges for any community system designed to treat hundreds of thousands of gpd is managing the process cost-effectively at the beginning of build out when the flows are low and intermittent. The fixed film MBBR process is unmatched when it comes to simplicity, ease of O&M and effciency especially under these conditions.
Because the biology adheres to the media and is retained in the treatment basin, the bio-reactor is self regulating and will adjust naturally over time to the organic and hydraulic loading on the system. Suspended growth processes don't have this luxury and costly to operate during a development build out.
For the most part, the Cave Springs WWTP is comprised of modular pre-fabricated vessels. The Lotus-ActiveCell reactors are constructed of 100% stainless steel and many of the ancillary components and tanks are fiberglass. Using high quality materials ensures a long life cycle and saves the municipality from costly repairs and rehab in the future.
To date only a small percentage of homes are currently on line as the developments are still under construction. But the savings of building a combined system netted a low capital equipment and installation cost of only $5,000/home.
Like Cave Springs, many towns and couties across the country are including decentralized and distributed wastewater infrastructure in their water resource management plans. Using a distributed network of municipally operated systems allows communities to probide cost effective infrastructure when and where it is needed. the systems can be designed specifically to schieve the standars required by their surrounding environment and treated water can be used as a resource.