In addition to the main product line, Avista offer a small selection of ancillary products which may be required for efficient operation of a membrane system. These include chlorine scavenger, a salt rejection improvement aid and a range of line corrosion inhibitors. For hybrid systems, a thermal antiscalant is also offered. The products are outlined below.
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In many cases, chlorine is present in the membrane plant feedwater by either direct or indirect injection. Municipal feedwaters typically contain some level of chlorine residual and water treatment plants inject chlorine in order to reduce biological activity in the pretreatment process. Because polymaide membranes have very little tolerance to chlorine and other oxidising agents, the chlorine must be de-activated to prevent permanent membrane damage. Anti-Chlor 30 is a 30% solution of sodium bisulphite and functions as a chlorine scavenger. The product addition rate may be calculated using Avista Advisor 3.
Polyamide membranes may lose some of their rejection charerecteristics as a result of oxidation or simply due to age. Phoenix liquid and powder resizing agents are available to coat the surface of partially oxidized/damaged polyamide membranes and improve salt rejection. Elements should always be cleaned prior to sizing.
Reverse osmosis permeate is often corrosive to downstream piping due to a low level of hardness and alkalinity. In the case of permeate from a seawater plant, the level of chloride will be disproportionately high. Corrosion may be prevented by applying a suitable inhibitor. The ViCoat product range includes formulations based on inorganic pyrophosphate, silicates and silicate/polyphosphate blends.
Vitherm 700 is a blended antiscalant developed for use in thermal distillation systems. Low application rates of Vitherm 700 are effective in preventing scale and metal oxide precipitates over the full range of operating temperatures.
