Question $1(117)$

$1\mathrm{.}1$ Compare the life cycle costs of fluorescent light bulbs and LED bulbs over $10$ years. Assume an initial cost of R$1$ for a fluorescent bulb and R$5$ for an LED bulb, with energy costs of R$0\mathrm{.}12$ per kWh and $1000$ hours of use per year. Fluorescent bulbs have $80$ watts and LED bulbs have $100$ watts. $(8)$

$1\mathrm{.}2$ You are tasked to design a manual bar screen to receive an average water flow of $20$ MLD $($Megaliters per day$).$ The screen thickness is $10mm$ with bar spacing of $30mm.$ The screen to be used in the approach channel will have $0\mathrm{.}65\frac{m}{s}$ maximum velocity and the inclination angle is $40$ with depth to width ratio of $1\mathrm{.}5.$

a$.$ Determine approach channel cross$-$sectional area, width, and depth. $(10)$

b$.$ Determine approach channel cross$-$sectional area, width, and depth. $(10)$

c$.$ Determine the bar cross$-$sectional area and net area. $(6)$

d$.$ Using the continuity equation, will the screen be sufficient? $(4)$

e$.$ Determine the number of screen bars. $(4)$

$1\mathrm{.}3$ Design rapid mixing tank treating $0\mathrm{.}08\frac{m^3}{s}.$ The rapid mixing time is $15$ seconds with depth to diameter of $0\mathrm{.}7.$

a$.$ What will be the cylindrical diameter of the tank? $(8)$

b$.$ What will be the surface area and depth of the tank? $(4)$

c$.$ What will be the detention time and is it acceptable? $(4)$

$1\mathrm{.}4$ Design single rapid sand filter for a flow of $0\mathrm{.}2917$ megaliters per day with $2\mathrm{.}5\%$ used for backwashing. The backwashing takes $30$ minutes per day with a filter capacity of $2000\frac{l}{h}\frac{?}{m^2}.$ Take $\frac{L}{B}=1\mathrm{.}3.$

a$.$ Determine filtration area, length, and breadth. $(12)$

b$.$ Determine the number of filtration units. $(4)$

$$ NOTE: This is a chemical engineering problem in design for environmental sustainability