In natural water, hardness is mainly caused by

What causes the temporary hardness in water?

The absorbent most commonly used in water and waste treatment is

Match the following:

Group 1 (Type of water impurity)

P. Hardness

Q. Brackish water from sea

R. Residual MPN from filters

S. Turbidity

Group 2 (Method of treatment)

1.     Reverse Osmosis

2.     Chlorination

3.     Zeolite Treatment

4.     Coagulation and Flocculation

In the EDTA titration method for determining the hardness of a water sample, the indicator used combines with the hardness-causing divalent cations to form a colored complex. The name of the indicator and the color of the formed complex are:

Consider the following statements about the design of large sewage pumping stations:

1. The velocity of flow in the rising main should be less than 0.8 m/s at any time.

2. Maximum velocity of flow is generally limited to 1.8 m/s and never allowed to exceed 3.0 m/s.

Which of the above conditions must be satisfied?

The chemical analysis of a water sample indicates the presence of the following cations and anions: Na⁺ = 25 mg/L, Ca²⁺ = 35 mg/L, Mg²⁺ = 55 mg/L, HCO₃^- = 225 mg/L, SO₄^2- = 220 mg/L, Cl^- = 79.2 mg/L. Calculate the carbonate hardness and non-carbonate hardness equivalent to CaCO₃.

The following data are given for a channel-type grit chamber of length 7.5 m:

1. Flow-through velocity = 0.3 m/s

2. Depth of wastewater at peak flow in the channel = 0.9 m

3. Specific gravity of inorganic particles = 2.5

4. g = 9.80 m/s², μ = 1.002 x 10^-3 N-s/m² at 20°C, ρ_w = 1000 kg/m³

Assuming Stoke's law is valid, what is the largest diameter particle that would be removed with 100% efficiency?

Alkalinity of water, in equivalent/litre (eq/litre), is given by

{HCO3–} + 2{CO32–} + {OH–} – {H+}

Where, { } represents concentration in mol/litre. For a water sample, the concentrations of HCO3– = 2×10–3 mol/litre, CO32– = 3.04 × 10–4 mol/litre and the pH of water = 9 .0 . The atomic weights are: Ca = 40; C = 12; and O = 16 . If the concentration of OH– and H+ are NEGLECTED, the alkalinity of the water sample (in mg/litre as CaCO3), is

Sedimentation basin in a water treatment plant is designed for a flow rate of 0.2 m³/s. The basin is rectangular with a length of 32 m, width of 8 m, and depth of 4 m. Assume the settling velocity of these particles is governed by the Stoke's law.

Given: density of particles = 2.5 g/cm3

density of water = 1g/cm3

dynamic viscosity of water = 0.01 g/(cm.s)

gravitational acceleration = 980cm/s2.

If the incoming water contains particles of diameter 25 µm (spherical and uniform), the removal efficiency of these particles is