During reverse osmosis water treatment system, the value of pollution index (SDI Apparatus) determines one of the important indexes of the water entering the reverse osmosis. It is the main means wether the entering water is up to the requirement of reverse osmosis device through examining water treatment process system in advance. The size of pollution index is crucial to life-span of reverse osmosis operation.
SDI value is determined by attenuation of water flow velocity, when water flow entering microfiltration membrane (outer dia.47mm, pore size:0.45µm). At pore size-0.45µm, colloid sustances more easily occlude filter membrane than hard particles (such as sand, dirt, rust, scale etc. ), so this pore size is usually used for determination of the SDI value. The attenuation of water flow velocity transformed into numerical value between 1 and 100, namely SDI value, the SDI value is smaller, the filter membrane is not more easily polluted and occluded by particles and colloid substances in water. Considering economy and efficiency roundly, the SDI value of the water entering the reverse osmosis device, is generally required under "5".
SDI47 pollution index (SDI APPARATUS), including pressure regulating valve, outer dia.47mm membrane filter box, microfiltration membrane piece and some required valve,joining pipe, connector etc. In addition, the apparatus system including a box of CN-CA mixed cellulose filter membrane pieces, absolutely reaching the requirement of ASTM method. Using this apparatus, must prepare a measuring cylinder and stopwatch for determining SDI value on-line.
Measuring cylinder----cubage 500 ml, min. scale 5ml
Stopwatch --------------precision 0.2 second
CN-CA mixed cellulose microfiltration membrane pieces(expendable)------outer dia.:47mm, Pore size: 0.45um;
1:Close water ball valve (2), prevent the water entering the measure apparatus.
2:Locate and connect installation of screw (1 ) of the measure apparatus with the place examinated.
3:Open the water ball valve (2 ),let water entering, gently pull the adjusting knob (10), and adjust the pressure to 207kpa.
4:Close the water ball valve (2 ).
5:Take down the membrane filter box . (Method of fetching the membrane box: push the valve( 4 ) connecting quickly upwards, the membrane filter box comes off automatically. Notice: Hold the membrane filter box properly while dismantling ,prevent the membrane filter box from damaging while coming off. )
6:Open membrane filter box after taking down , take out membrane filter box " O " type ring ,take out a piece of 0. 45µm membrane by nipper and put it in the support board of membrane filter box underpan(7), enclose and put " O " type ring in the normal position, and then, cover oneself up with the membrane filter box top cover (6) ,twist the screw (5 ) tightly to the proper degree.
7:Insert the membrane filter box in and connect the valve (4 )connecting quickly;
8:Open ball valve (2 ) slowly and expel the air bubble secretly from the membrane filter box, close up the water ball valve (2), and then twist
screw (5) tightly and completely.
9:Open ball valve (2 ), determine the time (t1:second) while filtering 500ml water sample, and let it filter continue.
10:After 5 , 10 and 15 minutes, determine the time (t2:second) while filtering 500ml water sample (notice: During testing entirely, the pressure must be in the range of 207 +/- 7kpa).
11:Determine the temperature of water (notice: Among examining entirely, the temperature must keep within change of one degrees Centigrade range).
12:SDI value (calculational methods)
P30 — The index of stopping up under water pressure strength in 207kpa;
Tt — Total examining the time (minute) is usually T15, at this moment P30 <75%, otherwise test T10 or T5, makes P30 <75%
t1 — t1 is the necessary time (second),while collect the water sample of 500ml initially.
t2 — After T1 (usually T15), necessary time (second),while collect 500ml water sample.