How to determine the Total dissolved solids (TDS) and Total suspended solids in the water? Kindly explain it?
Gibb's Rigid Module Gibb's module has an inlet pipe below the distributary bank. The pipe takes water from the distributary to a rising spiral, which is connected to the eddy chamber. This produces free vortex motion owing to which there is heading up of water (due to smaller velocity at larger radiRead more
Gibb’s Rigid Module
Gibb’s module has an inlet pipe below the distributary bank. The pipe takes water from the distributary to a rising spiral, which is connected to the eddy chamber. This produces free vortex motion owing to which there is heading up of water (due to smaller velocity at larger radius – a feature of vortex motion) near the outer wall of the rising pipe. The water surface thus slopes towards the inner wall. A series of baffle plates of appropriate size are attached to the roof of the eddy chamber such that their lower ends slope against the direction of flow. As the head increases, water banks up at the outer wall at the eddy chamber and strikes against the baffles and spins round in the compartment between two adjacent baffle plates. This results in the dissipation of excess energy an2 release of a constant discharge. The outlet is relatively more expensive, and its sediment withdrawing characteristic is also not good.
The following discharge formula was given by Gibbs:
Q = ro √2g (d1 + ho)1.5 [(m2 – 1)/m3 x loge m + 1/m loge m – (m2 – 1)/2m2]
where Q = discharge passing down the module,
ro = radius of the outer semicircle of the eddy chamber,
m = ro/ r1 = ratio of outer radius to inner radius,
r1 = radius of inner semicircle,
d1 = depth of water at inner circumference,
ho = head loss in inlet pipe.
The formula is based on the free vortex flow in which the velocity at any point varies inversely as the radius, and by Bernoulli’s theorem, the total energy of all filaments is constant. Gibb’s formula holds good only for his standard design in which m or (r0/r1) = 2 and (ho/D) = 1/7, where D is the difference of level measured from the minimum water level in the parent channel to the floor of eddy chamber.
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Vishwajeet Kumar
Determination of Total Dissolved Solids TDS in water is due to the dissolved salts and minerals in water which are usually present in the form of ions; ex- sodium, potassium, carbonates, sulphates etc. Sometimes these dissolved solids can be toxic and also causes formation of scales in pipes and henRead more
Determination of Total Dissolved Solids
TDS in water is due to the dissolved salts and minerals in water which are usually present in the form of ions; ex- sodium, potassium, carbonates, sulphates etc. Sometimes these dissolved solids can be toxic and also causes formation of scales in pipes and hence determination of the same is essential.
TDS can be determined by two methods:
Procedure-
Step1- Take an empty beaker and note down it’s weight, say- 20 g.
Step2- Put water sample in the beaker and take weight again, say-220 g which, means weight of water=220 g – 20 g=200 g.
Step3- Heat the beaker to evaporate water and once all the water is evaporated take the weight of beaker along with the residue, say-21 g which means weight of residue is= 21g – 20 g=1 g.
weight of residue= 1 g= 1000 mg
weight of water=200 g
Volume of water=200/1(density of water= 1 g/cc)
=200 cc=200 mL=0.2 litres
TDS=1000 mg/0.2 Litres= 5000 mg/L=5000 ppm.
*Note- when water is evaporated, dissolved solids in the form of ions combines to form solid residue.
2. TDS meter: Dissolved solids are usually present in water in the form of ions and ions conduct electricity. This principle is utilized in finding the TDS of water. TDS meter tip is dipped inside water which measures the amount of electricity getting conducted and this electricity value is calibrated to TDS value in ppm or mg/L. This method is very quick to use and is widely popular. Results of this test are approximate because all the dissolved solids present in water are not present as ions.
Determination of Total Suspended solids
Total Suspended solids are determined by Gravimetric Analysis in laboratory. Since water contains both dissolved as well as suspended solids, hence for the determination it is essential to separate the two solids.
First, water sample is filtered using 1.5 micron filter and the residual contents over filter contains suspended solids. This filter is kept inside oven at 104°C and taken out after an hour. The dried weight of filter along with dried residue is taken. After subtracting the weight of filter in this weight , the suspended solids weight is found out and by dividing the weight of suspended solids by volume of water, the Total Suspended Solids value in ppm or mg/L can arrived at.
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