The sewage passes through screen to remove solids that are over 3mm in sizes. They are collected and go to land fill.
The sewage then passes into a sedimentation tank where heavy sludge sink and light scums float, so they are separated from the liquid
a. The liquid components goes to an aeration tank where aerobic bacterias digest organic matters and consume extra Nitrogen and Phosphorus.
The aerated water also suppress the growth of anaerobic microbes.
b. On the other hand, sludge components goes into an anaerobic digester where anaerobic microbes digests the sludge, releasing CO2 and CH4 (methane) as byproduct
CH4 (methane) can be used for electricity generation.
Digested sludges can be used as compost (fertilizer).
Digested water are recycled back to the start of treatment plant to be re-treated.
The wastewater is then exposed to UV light to kill pathogens, and is released into the harbour.