Solids management at municipal wastewater treatment plants is crucial in maintaining operating efficiencies and permitted discharge levels. Drying beds and mechanical methods of dewatering bio-solids can be labor intensive and inefficient for rapid solids removal. Miratech Geotube' Dewatering Technology offers munic-ipalities a cost effective solution for rapid solids removal and long term solids management.
In the spring of 2003. the city of Eatonton, Georgia faced potential discharge permit violations due to increased solids levels that hampered operations at their two activated sludge wastewater treatment plants. Solids within the aeration lagoons were exceeding 900 on the Settling Meter Test due to higher than usual rainfall and the inability to use their on-site drying beds for solids wasting. With a tight budget and labor limitations, the plant superintendent was faced with the dilemma of taking immediate action to rapidly reduce solids inventory in a short time, but without exceeding his operating budget. The city was also searching for a long term economical method for solids management without capital expenditures.
Miratech's Geotube Dewatering Technology was chosen for rapid removal of solids from the cities two 350 mgd wastewater treatment plants. The Geotube' was chosen because it offers:
- High volume containment
- Rapid dewatering
- Effective filtration
- Extremely high quality effluent
- 85% to 90% reduction of BOD in the effluent
- No capital expenditure
- No special equipment
- Use existing employees
The Geotube container is a 30 ft. circumference flexible, dewatering tube fabricated from specially designed, high strength industrial textiles, these engineered textiles allow for contain-ment of fine particles of solids, yet are permeable to allow for rapid dewater¬ing. The Geotube container is tailored specifically for the municipal water and wastewater market to fit within drying beds and other designated plant locations.
A total of 8 sections of 50 ft long Geotube containers are being used per year to contain and dewater 3 million gallons of waste with 1% solids. Each of the two plants will deploy 4 Geotube sections in their existing drying beds. Once per week at each plant, 30.000 gallons of waste will be pumped from the digester into the Geotube container. As the waste flows through an inline mixer, 15 ppm of a .5% solution of a cationic polymer is injected into the waste stream to facilitate flocculation and precipitation of the solids. The flocculated waste then flows into one of the Geotube containers. Clear effluent flows through the porous surface of the textile as the solids are contained. This dewatering process allows for the 80% to 90% volume reduction of waste. The process of filling and dewatering is repeated weekly until the Geotube container is filled to capacity.
Within 180 days following installation of the Geotube Dewatering Technology at both plants, more than 1.5 million gallons of bio-sludge has been pumped from the digesters into the Geotube containers and dewa-tered. Settlement Meter Tests of solids taken from the aerator lagoons indicate levels below 350 at both plants. Both locations are operating at well below permitted discharge levels and within efficient parameters. The plants are on track to remove and dewater a total of 3 million gallons of waste before the end of 2003. These results were achieved without capital expenditures and without exceeding the City of Eatonton's operating budget. Because of this success, the Geotube Dewatering System has become the long term solution for solids management.