PRE-TREATMENT SYSTEMS

HydroTech offers pre-treatment systems and components as preliminary filtration stage for our membrane systems or for stand-alone customer-specified applications. Depending on the raw water condition, our team of engineers can recommend a configuration of filtration media, active carbon and/ or softening to provide the right combination of value and features for the end user. 

Media filtration is used to reduce the level of suspended solids (turbidity) in incoming feed water. Suspended solids consist of small particles such as silt, clay, grit, organic matter, algae and other microorganisms.

Incoming feed water that is high in suspended solids can cause significant pressure drop and reduce the effectiveness of downstream filtration equipment such as reverse osmosis.

A properly designed and sized multi-media filter system would capture these mechanical contaminants, therefore preventing premature fouling of RO membranes.

A multi-media filter is suggested when the Silt Density Index (SDI) value is greater than 3 or when the turbidity is greater than 0.5 NTU.

A multi-media filter typically contains several layers of different media. Some common types of media include anthracite, sand, garnet, zeolite, etc. The layered media arrangement allows for gradual filtration where the larger dirt particles are removed near the top of the media bed and the smaller dirt particles are being retained deeper and deeper in the media. This allows the entire bed to act as a filter allowing much longer filter run times between backwash and more efficient particulate removal. 

Carbon filters are using granular activated carbon (GAC) that has been treated to be extremely porous to remove contaminants and impurities, using chemical adsorption. When the water flows through active carbon filters the chemicals stick to the carbon resulting in purer water output.

Carbon filters are a necessary pre-treatment step for a reverse osmosis system where the feed water contains chlorine. Free chlorine needs to be removed from the feed water stream before entering the RO system to prevent damage to the RO membranes.

Feed water to RO systems needs to be less than 5 GPG of hardness (85.5 mg/l) to prevent hardness deposits onto the surface of the RO membranes. For smaller RO systems (<10,000 GPD), HydroTech offers water softeners in a single or twin tank configuration.