Membrane cleaning equipment

The main cost factors are represented by equipment depreciation, membrane replacement, and electric power consumption. The other costs (man power and water consumption) are of minor influence. Membrane filtration plants equipped with a low level of automation require only a few hours of attention and direct surveillance by the operator per day. Direct surveillance of membrane filtration equipment is necessary at times when batches need to be changed or during membrane cleaning. The electric power consumption is associated with the use of pumps to move the viscous yeast slurry over the membrane surface, and its estimation is relatively straight forward. 

Besides its direct use in the final product, water is used in breweries as a utility, for purposes such as cleaning, steam generation, etc. Another common utility in breweries are gases, such as air and carbon dioxide, which sometimes might contain impurities that need to be removed in order to ensure the quality and uniformity of the hnal product. Besides traditional methods, i.e., activated coal treatment, purification of utihties can also be successfully done by membrane filtration. Some membrane manufacturers (i.e., Pall Corporation, Donaldson Ultrafilter Inc., Sartorius, Millipore, CPM, etc.) offer commercial membrane separation equipment that is specihcaUy designed for the purification of water, steam, air, or carbon dioxide. This enables breweries to produce sterile and particle-free utihties for the brewing processes. 

Membrane cleaning involves the removal of a substance that is not an integral part of the membrane material [176]. The process must remove fouling deposits and must restore the normal capacity and separation characteristics of the equipment [175]. The cleaning process is usually divided into two main steps rinsing and chemical cleaning. 

Equipment used to produce biotech products should be qualified for design, installation, operation, and performance [15]. The aging and continued performance of re-used process materials such as column resins is an important consideration during the validation of a biotech process. Demonstration of microbial control during processing is also a critical component of process validation, particularly in difficult to clean equipment such as alBnity columns or ultrafiltration membranes. Finally, consistent and reasonable step yield of individual unit operations can be verified during consistency and commercial product manufacturing. 

Gleaning. Fouling films are removed from the membrane surface by chemical and mechanical methods. Chemicals and procedures vary with the process, membrane type, system configuration, and materials of constmction. The equipment manufacturer recommends cleaning methods for specific apphcations. A system is considered clean when it has returned to >75% of its original water flux. 

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... 

Economic Yield Both in a high-value protein separation and in a low-value commodity concentration, economic yield is vital. Economic yield is defined as the fraction of useful product entering the process that leaves it in salable form. The yield equations used in the industry focus on retention, so they deal only with direct losses through the membrane. These losses result both in direct (product not sold) and indirect costs from a waste stream whose disposal or subsequent use may be more expensive when it is contaminated by macrosolute. There are additional indirec t losses, mainly product left in the equipment, particularly that left adhering to the membrane. Costs of cleaning and disposal or this indirect loss, while hard to measure, are usually higher than the cost of product lost through the membrane. 

Fig. 3.29 Resistances of the 38 sensor segments of a Sn02-microarray equipped with Si02-membrane during alternating exposure to carbon monoxide contaminated humid air and clean air with the same relative humidity...

The by-product of sap concentration by an RO, permeate, is also used in maple operations as a source of very clean water. Due to the low mineral concentration of permeate water, it is used for cleaning tubing and evaporator equipment, as well as the RO membrane itself, which should be run through a wash and rinse cycle after each use. The chemicals and dosage to be used are specified by the membrane and RO manufacturers, and should be carefully followed to avoid damaging the membrane or contaminating the sap concentrate. 

HERO—High-Efficiency RO Process Boosts Recovery Ratios, Cuts Cleaning Frequency," GE Water Process Technologies, www. gewater.com/products/equipment/spiral membrane/HERO.jsp... 

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