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).
In the following table, identify the correct set of associations between the entries in Column - 1 and Column-2.
| Column-1 | Column-2 |
|---|---|
| P: Reverse Osmosis | III: Concentration Polarization |
| Q: Trickling Filter | I: Ponding |
| R: Coagulation | IV: Charge Neutralization |
| S: Adsorption | II: Freundlich Isotherm |