Test: Quality Control of Water Supply - 2 - Civil Engineering (CE) MCQ

An approximate analysis for TDS is often made by determining the electrical conductivity of the water. The ability of water to conduct electricity is called specific conductance and it is a function of its ionic strength. Unfortunately, specific conductance and concentration of TDS are not related on a one to one basis. Only ionized substances contribute to specific conductance. Organic molecules and compounds that dissolve without ionizing are not measured. Additionally, the magnitude of specific conductance is influenced by the valence of the ions in the solution, their mobility and their relative numbers. The temperature also has an important effect with specific conductance increasing as the water temperature increases. The ions usually accounting for majority of TDS in natural waters are Na, Ca, Mg, HCO^-₃, SO^2-₄, Cl^-, etc. Hence their presence increases the electrical conductivity of water.

Salmonella typhi and Salmonella paratyphi (bacteria) cause enteric fever.
Enteric Cytopathogenic Human Orphan ECHO (virus) cause aseptic meningitis, epidemic exanthem, infantile diarrhoea.
Entamoeba histolytica (protozoa) cause dimebiasis (amebic dysentry, amebic enteritis, amebic colitis). Echmococcus (helminth) cause enchinococcosis (hydlatidosis, granulosis, dog tapeworm).

Monovalent cations impart pseudo-hardness. Hardness is the concentration of multivalent cations.

Nephelometer is based on scattering principle for measurement of turbidity, Ituses formazin, a chemical compound, for standard. Formazin is more reproducible standard than SiO₂. Tintometer is a color measuring instrument which compares colour of water in Nessler tubes which contain solutions of platinum Cobalt dissolved in water.

CO₂ reacts with water to form carbonic acid.

A fluoride concentration of less than 0.8-1.0 ppm may be harmful and may cause dental caries (tooth decay) due to the formation of excessive cavities in the teeth of young children during calcination of their permanent teeth. Higher fluoride concentrations, greater than 1.5 ppm or so, may again be harmful, causing spotting and discolouration of teeth, (a disease called fluorosis), which with continued excessive consumption of fuorides, may even cause deformation of bones.