Figure 2 Solids Loading vs. Membrane Performance
Click here to enlarge imageIn addition to the flexibility of operation described above, the reduced membrane area and the low solids concentration in the membrane tank can result in reduced capital and O&M costs. As membranes typically represent among the highest capital expenditures in new plant construction, advanced treatment prior to the membranes can reduce the quantity of membranes and minimize the cost of ownership. Additionally, the equipment and chemicals needed to clean the membranes also will be reduced, further reducing O&M costs.
Case Study
One of Aqua-Aerobic Systems’ multiple-barrier processes can be found in the Australian island of Tasmania. The St. Helens Wastewater Treatment Plant was originally designed as a lagoon system. Recently, the Environmental Protection Authority of Australia imposed more stringent effluent requirements and the plant was forced to meet a BOD of 2 mg/l, TSS of 2 mg/l, Total Nitrogen of 5 mg/l and Total Phosphorus of 0.1 mg/l.
In order to meet these new BNR requirements, the engineer and owner evaluated nine different membrane technologies, all but one were MBR processes. After thoughtful consideration of installed costs, operation and maintenance, operability and flexibility, the decision was made to upgrade to the AquaMB Process®. Recently commissioned, this facility includes a dual basin AquaSBR® system with retrievable fine bubble diffusers followed by a 2-disk AquaDisk® cloth media filter with the effluent filtered through pressure membranes. The system is sized for 0.4 mgd average and 0.8 mgd peak flow and designed with the flexibility to operate in single basin mode during low influent periods. The treated effluent is discharged into nearby St. George Bay, which is used for sensitive aquaculture.
About the Authors:
Manuel de los Santos is Senior Applications Engineer, Biological Processes & Membranes, at Aqua-Aerobic Systems Inc. He possesses an M.S. degree in Sanitary and Environmental Engineering from the Universidad de Cantabria, Spain. He has five years of application engineering experience in the wastewater treatment industry with skills in design, application and technical support for biological processes and membranes. Terence K. Reid, P.E., is Product Manager, Biological Processes & Membranes. He has over 16 years experience in the wastewater field with responsibilities that include process and applications engineering, mechanical design and operator training. He has authored articles in the areas of batch reactor, nutrient removal and membrane technologies.