For a sample of water with the ionic composition shown in the figure below, the carbonate and noncarbonate hardness concentrations (in mg/l as $${\mathrm{CaCO}}_3$$), respectively are:

Some of the nontoxic metals normally found in natural water are

A straight 100 m long raw water gravity main is to carry water from an intake structure to the jack well of a water treatment plant. The required flow through this water main is 0.21 $$m^3/s$$. Allowable velocity through the main is 0.75 m/s. Assume f = 0.01, g = 9.81 $$m/s^2$$. The minimum gradient (in cm/100m length) to be given to this gravity main so that the required amount of water flows without any difficulty is _____.

Three rigid buckets, shown as in the figures (1), (2) and (3), are of identical heights and base areas. Further, assume that each of these buckets have negligible mass and are full of water. The weights of water in these buckets are denoted as W₁, W₂, and W₃ respectively. Also, let the force of water on the base of the bucket be denoted as F₁, F₂, and F₃ respectively. The option giving an accurate description of the system physics is