Maintenance cleaning for membranes
First Claim
1. A method for cleaning one or more membranes normally immersed in water containing solids and used to produce a permeate on the insides of the membranes, comprising the steps of:
- performing one or more cleaning events per week, wherein, each cleaning event comprises the steps of flowing a chemical cleaner through the membranes to provide a chemical cleaner in or adjacent the membranes for a period of time; and
, the cleaning events reduce the frequency of necessary recovery cleanings of the membranes.
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Accused Products
Abstract
A method of cleaning ultrafiltration or microfiltration membranes reduces the rate of decline in the permeability of the membranes so that intensive recovery cleaning is required less frequently. In one aspect, cleaning events using a chemical cleaner are started before the membranes foul significantly and are repeated between 1 and 7 times per week. The product of the concentration of the chemical cleaner expressed as an equivalent concentration of NaOCl and the duration of all cleaning events is between 2,000 minutesmg/l and 30,000 minutesmg/l per week. When performed in situ, each cleaning event comprises (a) stopping permeation and any agitation of the membranes, (b) backwashing the membranes with a chemical cleaner in repeated pulses and (c) resuming agitation, if any, and permeation. The pulses last for between 10 seconds and 100 seconds and there is a time between pulses between 50 seconds and 6 minutes. Each cleaning event typically involves between 5 and 20 pulses. In another aspect, cleaning events using a pulsed backwash of heated water are similarly started before the membranes foul significantly and are repeated between twice a day and once every two days.
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Citations
61 Claims
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1. A method for cleaning one or more membranes normally immersed in water containing solids and used to produce a permeate on the insides of the membranes, comprising the steps of:
performing one or more cleaning events per week, wherein, each cleaning event comprises the steps of flowing a chemical cleaner through the membranes to provide a chemical cleaner in or adjacent the membranes for a period of time; and
,the cleaning events reduce the frequency of necessary recovery cleanings of the membranes. - View Dependent Claims (2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 41, 43)
- 6. The method of clam 1 where in the cleaning chemical is an oxidant.
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35. A method for cleaning one or more membranes normally immersed in water containing solids and used to produce a permeate on the insides of the membranes, comprising the steps of:
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(a) performing recovery cleanings of the membranes from time to time; and
,(b) between recovery cleanings, performing one or more cleaning events per week, each cleaning event comprising the steps of flowing a chemical cleaner through the membranes to provide a chemical cleaner in or adjacent the membranes for a period of time. - View Dependent Claims (36, 37, 38, 39, 40, 42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61)
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Specification