For a standard polyamide thin$-$film composite membrane system, what is the typical purpose of upstream acid injection?

a$.$ Reduce biofouling potential

b$.$ Reduce colloidal fouling potential

c$.$ Reduce scaling by calcium sulfate

d$.$ Reduce scaling by barium sulfate

e$.$ Reduce scaling by strontium sulfate

f$.$ All of the above are correct

g$.$ None of the above is correct

A germicidal UV unit ahead of an RO unit inactivates $90\%$ of the bacteria entering the unit. If around $50$ bacteria enter the UV unit in each milliliter $($mL$),$ around how many bacteria enter the RO unit in each milliliter?

a$.0$

b$.2$

c$.5$

d$.7$

e$.10$

f$.20$

g$.$ None of the above is correct

Chemically cleaning both stages of an RO unit at the same time:

a$.$ Is the most efficient for moderate to severe biofouling

b$.$ Is the most efficient for moderate to severe colloidal fouling

c$.$ Is the most efficient for moderate to severe scale removal

d$.$ Both a$.$ & b$.$ are correct

e$.$ Both b$.$ & c$.$ are correct

f$.$ a$.,$ b$.$ and c$.$ are correct

g$.$ None of the above is correct