You are the newly$-$appointed engineer$/$scientist recruited to improve management and control of the operation of the water treatment plant of a city. The city obtains raw water from a dam and the water is treated in a conventional drinking water treatment plant to produce water that complies with drinking water quality requirements. However, serious complaints about the drinking water quality have been received from consumers during the past year and analytical reports from an independent laboratory have also caused concern. It is your task to evaluate the operation of the plant and to develop a plan of action to improve plant performance and reliability. Answer the following questions in sufficient detail to demonstrate your competence to perform this task.

$($i$)$ Explain what is meant by a multiple barrier safeguarding approach to protect water quality. $(4)$

$($ii$)$ During your investigations you found that the turbidity in sandfilter effluent varies between $0\mathrm{.}5$ and $1\mathrm{.}5$ NTU. Do you regard this as a problem? Motivate your answer? Discuss possible causes for this variation in turbidity and suggest preventative corrective actions. $(8)$

$($iii$)$ One of the most frequently reported complaints is about occasional poor taste and odour of the drinking water. Give an overview of three possible causes of this problem, the substances that may cause the problem and the different methods to deal with this problem. $(8)$

$($iv$)$ The most serious problem reported in the laboratory reports is the presence of indicator organisms in some water samples collected at certain household sampling points. Although this points to problems with disinfection $($chlorination is used$),$ there are many factors that can affect the effectiveness of the process. Give an overview of all the factors that you consider must be considered and indicate in each case what the effect of the specific factor is$.(8)$

$($v$)$ The Department of Water and Sanitation introduced Blue Drop Certification that can be awarded to water service authorities. Briefly describe what this certification seeks to achieve and discuss some of the most important aspects that the certification process considers. $(8)$