Cleaning ultrafiltration water treatment

Eor water-treatment processes such as drinking water or potable water production, reverse osmosis (desalination), nanofiltration, and ultrafiltration are mainly used. In these processes often a microfiltration stage is implemented as the first cleaning stage for the removal of dissolved organic matter, colloids and particles from the source. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

A modular pilot size plant involving coagulation/flocculation, centrifugation, ultrafiltration, and sorption processes was designed and constmeted by Benito et al. [13] for the treatment of oily wastewaters. Empirical equations developed by Shaalan [65] predict the impact of water contaminants on flux decline. These formulae enable decision-making concerning a suitable water pretreatment scheme and also selection of the most appropriate cleaning cycle. 

J. Lindau and A. S. Jonsson, Cleaning of ultrafiltration membranes after treatment of oily waste water. Journal of Membrane Science 87, 71-78 (1994). 

In many countries the regulations for disposal are very exigent, and in this way treatment plants must treat the backwash water that is used during the normal operation. In the United Kingdom, there is a drinking water plant that used two units of ultrafiltration in its process. The first one is a pretreatment for RO units, and the second one is to treat the water used in the cleaning of the membranes. 

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