An MLE process might have a lower annual cost $($e$.$g$.$ aeration$/$electricity etc.$)$ than a conventional system. Why is that possible? Select all that might apply $($this is a multiple answer question, not a multiple choice question like those before and after it$).$

The MLE process might not require alkalinity addition

The MLE process oxidizes part of the influent BOD using nitrate

The MLE process nitrate recycle is at a high rate and speeds up the kinetics of nitrification

The MLE process has PHA storage in the anoxic zone with $N$ uptake in the aerobic zone

$1$

$2$

$3$

$4$