The membrane pollution and its control method

Abstract: the membrane pollution problem can be divided to precipitate pollution, adsorption pollution, biological pollution. On their own, the formation mechanism of or causes for the analysis, and put forward the corresponding control method.
Keywords: film precipitation pollution pollution mechanism of biological adsorption pollution control method

Membrane pollution means in the membrane filtration process, the water particles, colloid particles or solutes macromolecular because there and membrane physical and chemical interaction or mechanical function and cause in the membrane surface or film hole adsorption, sedimentary cause membrane aperture smaller or congestion, membrane separation characteristics through flow and produce the irreversible change phenomenon [1].

In fact, the reliability of the film is the application of membrane technology that one of the keys, and the pollution problem is the decisive factor of influence the reliability. According to the survey, ultrafiltration speaking, is still the main problems of pollution, pollution will eliminate makes the ultrafiltration process efficiency increased by more than 30%, make investment reduced by 15%, and can improve the separation effect, makes the ultrafiltration range broaden [2]. On membrane pollution causes the kinds and analysis of the specific, will help take appropriate measures to eliminate or decrease its adverse effects.

1 precipitation pollution

With pressure for driving force of membrane technology have reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and micro filter (MF). According to different membrane and the relationship between water particles [3], it can be seen that pollution on the precipitation and the influence of the NF RO particularly remarkable.

When the concentration of salt in the raw water more than its solubility, will be in a membrane formation precipitation or scaled. Common people of pollutants by attention is calcium, magnesium, iron and other metal deposits, such as hydrogen chloride, carbonate and sulfate, etc.

In solution have chemical reaction: x Ay-+ y Bx + = AxBy

When not considering the interaction between the salts, solubility product Ksp = γ xA [Ay-x γ yB [Bx +] y is constant. Among them, the γ A, γ B for free ion A and B average activity coefficients; [A], [B] for the solution concentration Moore; X, y for chemical proportion coefficient. Average activity coefficients are ionic strength [I] function to assess:
A log γ = 0.509 ZAI1/2.
Log γ B = 0.509 ZBI1/2;
ZA, ZB the combining power of the ion for free. To dilute solution, such as the most natural water, its activity coefficients γ A, γ B is equal to 1.

As shown in figure 1 shows, feeding liquid, concentrate, penetration liquid concentration for Cf respectively, Cr, Cp.