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          行業資訊 公司動態

          水處理設備反滲透膜膠體污染的預處理

          2019-08-08

          膠體是非常小的粒子,其尺寸在0.3~1.0μm范圍。膠體帶電荷并且是懸浮體,它們彼此之間互相排斥。膠體可能來自于下述任何一種來源:①進水穿過或越過黏土質結構就可能帶硅酸鋁膠體;②碳鋼泵、管道、過濾器的腐蝕產物可能存在鐵膠體;③用明礬或不適當的澄清劑預處理的水可能含有氫氧化鋁膠體。
           
          Colloids are very small particles with sizes ranging from 0.3 to 1.0 um. Colloids are charged and suspended, and they repel each other. Colloids may come from any of the following sources: 1) Aluminum silicate colloids may be present when water enters or passes through clayey structures; 2) iron colloids may exist in corrosion products of carbon steel pumps, pipes and filters; 3) Aluminum hydroxide colloids may be present in water pretreated with alum or improper clarifiers.
           
          反滲透膜的膠體污堵是由于在反滲透膜設備運行期間的反滲透處理過程中,膠體的凝聚和在反滲透膜上凝聚物質的沉積。
           
          Colloidal fouling of reverse osmosis membranes is due to the coagulation of colloids and the deposition of condensates on reverse osmosis membranes during the reverse osmosis treatment process during the operation of reverse osmosis membrane equipment.
           
          一.污泥密度指數
           
          I. Sludge Density Index
           
          膠體的含量(n)是由SDI確定的。SDI是從水在207kPa工作壓力下,通過0.45μm微孔過濾器的堵塞速率得出的。雖然SDI的測量時不絕對的,但它是已發現的測量膠體含量的最好方法。人們已經獲得在滲透器中SDI與膠體沉積速率二者之間的相互關系。另一種測量膠體含量的方法(濁度和顆粒計算)是不令人滿意的。顆粒計算對亞威顆粒范圍不能給予的結果。濁度是粒子的尺寸、形狀及濃度的函數。因而,濁度與從一位置到另一位置的膠體污堵之間沒有相關性存在。
           
          The colloid content (n) is determined by SDI. SDI is derived from the clogging rate of water through 0.45 um microporous filter under 207 kPa working pressure. Although SDI measurement is not absolute, it is the best method to measure colloid content that has been found. The relationship between SDI and colloid deposition rate in permeators has been obtained. Another method for measuring colloid content (turbidity and particle calculation) is unsatisfactory. Particle size calculation can not give the results of Yawei particle size range. Turbidity is a function of particle size, shape and concentration. Therefore, there is no correlation between turbidity and colloidal fouling from one location to another.
           
          井水SDI通常大約是1.0,并且不需要任何用于去除膠體污堵的預處理。如果井水的SDI超過1.0,可能的原因是:地表水侵入淺井;鐵腐蝕產物存在;生物污染的存在;膠體磺化的存在。地表水含有大量的膠體物質,并且SDI值在10~175范圍。
           
          Well water SDI is usually about 1.0 and does not require any pretreatment for removing colloidal fouling. If the SDI of well water exceeds 1.0, the possible reasons are: surface water intrudes into shallow wells; iron corrosion products exist; biological pollution exists; colloidal sulfonation exists. Surface water contains a large amount of colloidal substances, and SDI values range from 10 to 175.
          二.反滲透膜膠體預處理
           
          II. Colloid Pretreatment of Reverse Osmosis Membrane
           
          SDI與污堵之間的經驗關系表示為SDI必須是3.0或再小些,才能使反滲透設備的污堵速率減到最小值,以便使反滲透系統長期穩定運行。必須注意市政水處理工廠處理的地表水通常SDI大于6。因此,這些水如果不進一步處理,將在反滲透膜元件上產生膠體附著。
           
          The empirical relationship between SDI and fouling indicates that SDI must be 3.0 or less in order to minimize the fouling rate of reverse osmosis equipment so that the reverse osmosis system can run stably for a long time. It must be noted that surface water treated by municipal water treatment plants usually has SDI greater than 6. Therefore, if the water is not further treated, colloidal adhesion will occur on the reverse osmosis membrane elements.
           
          1. 硅藻土(DE)過濾器
           
          1. Diatomite (DE) filter
           
          如果原始的SDI在4~5內,硅藻土過濾器能夠用來減小SDI到2.0;如果膠體的含量非常高,在過濾器中的壓降將迅速增加。
           
          If the original SDI is within 4-5, diatomite filter can be used to reduce SDI to 2.0; if the colloid content is very high, the pressure drop in the filter will increase rapidly.
           
          2. 壓力介質過濾器
           
          2. Pressure Media Filter
           
          通過小型試驗可用來測定膠體減少的度數,為給定水質選擇一種最佳的濾料或濾料組合。
           
          A small scale test can be used to determine the degree of colloid reduction and to select an optimal filter material or combination for a given water quality.
           
          3. 凝聚
           
          3. Condensation
           
          在管道中和凝聚——絮凝——過濾是用來減少膠體含量,使SDI低于3.0的兩個基本工藝。為此必須采用適用的混凝劑,調整混凝劑的濃度,以及保證適當的混合和停留所必需的時間。必須進行現場試驗來確定最佳工況。監視和控制預處理系統是很重要的,這樣能連續生產提供品質好的成品水質。膠體的含量隨季節的變化也可能將牽涉到改變混凝劑濃度的問題。
           
          In pipeline neutralization, coagulation, flocculation and filtration are two basic processes to reduce colloid content and make SDI less than 3.0. Therefore, it is necessary to use suitable coagulants, adjust the concentration of coagulants, and ensure the proper mixing and retention time. Field tests must be carried out to determine the optimum operating conditions. It is important to monitor and control the pretreatment system so that the quality of finished product water can be continuously produced. The seasonal variation of colloid content may also involve the change of coagulant concentration.
          4. 膠體的穩定
           
          4. Colloidal stability
          速率常數k2與膠體穩定性有直接的關系。如果提高膠體穩定性,膠體污堵速率將降低。在理論上有幾種穩定膠體的方法。然而,僅僅發現的實踐方法是水軟化。也就是原水經過陽離子交換樹脂,二價和少量三價鐵離子與鈉離子交換。軟化增加膠體2倍厚度和有效電荷的電量。這兩者有效地增加膠體穩定性并延遲凝聚。測量膠體ζ電位能確定交替的穩定性。ζ電位通常在軟化水之后增加一倍。為了軟化,給的有效的穩定性必須是最近完成尺寸和適當的再生是極其重要的。
           
          The rate constant K2 is directly related to the stability of colloids. If the stability of colloid is improved, the fouling rate of colloid will decrease. There are several methods of stabilizing colloids in theory. However, the only practical method found is water softening. That is to say, raw water is exchanged with sodium through cation exchange resin, divalent and a small amount of trivalent iron ions. Softening increases the colloid thickness by two times and the effective charge. Both of them can effectively increase the stability of colloids and delay coagulation. Alternating stability can be determined by measuring colloid_potential. _potential usually doubles after softening water. In order to soften, it is extremely important to give effective stability to the recently completed size and proper regeneration.

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