By Michael Sheedy, Phillip Simmons, Rusi Kapadia, Eco-Tec Inc.
Pretreatment is crucial to the operation of all water treatment equipment. This is particularly true for reverse osmosis units and most ion exchange columns. These technologies require TSS of 0.1-0.5 mg/L, turbidities of 0.1-1NTU, and SDIs values <5 and ideally <3. Media filtration is the lowest cost pretreatment option, however high levels of filtration efficiency can be difficult to achieve when using conventional media. This paper describes a filtration system that uses a unique micro-media. The small particle size of this media ensures a high level of filtration efficiency, while still maintaining the benefit of a relatively lower capital cost and high solids loading. Case studies are presented for the treatment of various waters.
Due to its low cost, simple and reliable operation granular media filtration has historically been amongst the most common of pretreatment methods. However, there is a growing requirement for improved total suspended solids (TSS) removal. The result has been a move towards membrane based pretreatment processes such as microfiltration and ultrafiltration. Without question, the absolute filtration barriers that these technologies utilize have resulted in an increase in removal efficiencies. However, this improvement is counter balanced by relatively higher capital and operating costs.