Question $3$

$($i$)$ List and describe two $(2)$ sludge digestion techniques$/$processes in wastewater treatment that can be used before final disposal. In addition, highlight the final products from such digestion processes.

$[3+3+2+2$ marks $]$

$($ii$)$ The main objective of sludge thickening and dewatering is reduction of the water content in the sludge to reduce its volume. Explain the process of Dual Air Flotation $($DAF$)$ thickening. If the flow and surface area a DAF thickener are $600\frac{m^3}{d}$ and $175m^2$ respectively, calculate hydraulic loading rate.

$[2+2$ marks$]$