Q1: The rate of accumulation of sludge per person per year, is

ANS:C - 20 litres

The rate of accumulation of sludge per person per year refers to the average amount of sludge, typically composed of solid waste and organic matter, that is generated and collected from wastewater treatment processes over the course of a year for each individual served by the sewage system. The estimate of around 20 litres per person per year represents a general approximation based on factors such as population density, wastewater characteristics, treatment efficiency, and infrastructure development. It accounts for the volume of sludge produced as a byproduct of treating wastewater to remove pollutants and solids before discharging it back into the environment. It's important to note that this estimate can vary depending on various factors, including regional differences in population, lifestyle, water usage patterns, and the effectiveness of wastewater treatment technologies employed in different areas. Additionally, advancements in treatment processes and changes in population demographics can also influence the rate of sludge accumulation over time. Overall, while the estimate of 20 litres per person per year serves as a general guideline, actual rates may vary based on local conditions and practices in wastewater treatment and disposal.