A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is $250 \mathrm{~m}^3$, and the biomass concentration in the tank is $3000 \mathrm{mg} / \mathrm{L}$. Analyses results showed that a biomass concentration of $10 \mathrm{mg} / \mathrm{L}$ is present in the treated effluent from the secondary sedimentation tank of the ASP. Sludge wastage from the system is at a rate of $5000 \mathrm{~L} /$ day with a biomass concentration of $10000 \mathrm{mg} / \mathrm{L}$. The system is in steady state condition.

The biological sludge residence time (BSRT) of the system (in days) is _________ (round off to one decimal place).

A settling chamber is used for the removal of discrete particulate matter from air with following conditions. Horizontal velocity of air $=0.2 \mathrm{~m} / \mathrm{s}$; Temperature of air stream $=77^{\circ} \mathrm{C}$; Specific gravity of particle to be removed $=2.65$; Chamber length $=12 \mathrm{~m}$; Chamber height = 2 m ;

Viscosity of air at $77^{\circ} \mathrm{C}=2.1 \times 10^{-5} \mathrm{~kg} / \mathrm{m} . \mathrm{s}$;

Acceleration due to gravity $(\mathrm{g})=9.81 \mathrm{~m} / \mathrm{s}^2$; Density of air at $77^{\circ} \mathrm{C}=1.0 \mathrm{~kg} / \mathrm{m}^3$;

Assume the density of water as $1000 \mathrm{~kg} / \mathrm{m}^3$ and Laminar condition exists in the chamber.

The minimum size of particle that will be removed with 100\% efficiency in the settling chamber (in $\mu \mathrm{m}$ ) is ___________ (round off to one decimal place).

A hydraulic jump occurs in an open channel when the slope of the channel changes from__________ .

Consider steady flow of water in the series pipe system shown below, with specified discharge. The diameters of Pipes A and B are 2 m and 1 m , respectively. The lengths of pipes A and B are 100 m and 200 m , respectively. Assume the Darcy-Weisbach friction coefficient, $f$ as 0.01 for both the pipes.

The ratio of head loss in Pipe-B to the head loss in Pipe-A is ___________ (round off to the nearest integer).