Question

discuss the pros and cons of ocean outfalls versus injection of sewage effluent into coastal aquifers. In your assessment of the different scenarios, consider effects of: • Dilution • Redox conditions • Biological degradation • Bioaccumulation (or bioconcentration) • Photolysis • Residence time

Answer 1

What is ocean outfall-

A ocean outfall is a pipe that discharges municipal or industrial waste into the sea water. Most of the time this pipe or tunnel discharges under the water. This contains industrial waste water, stormwater, sewer overflows, etc

There are certain pros as well as cons to this method which is as follows

PROS-

Some pollutants which are very dangerous and contains pathogens as well as organic waste are discharged into the water and natural dilution of it takes place.

The die off rate of pathogens increases due to the increase in the distance of pathogens from the shore .

It is very cost effective than the other advanced waste treatment plants .

Sewage field is submerged under the water because of the depth at which it is released into the water

Only preliminary treatment of waste water is done which is 10 times cheaper than the secondary treatment which is done in waste management centres

CONS-

Marine outfall for partially treated waste can cause major pollution for sea life

Bioaccumulation of toxins is a major threat which can affect adversely on the sea life

Acclomeration or flocculation is observed due to grease present in the ocean outfall

Grease and wax interface with the dispersion process which results in the bacteria reaching to remote locations where concentration of bacterial predators is low which results In their low die off rate.

Residence time of an element is the average time that it remains in solution in seawater if waste in ocean outfall has more residence time then it is harmful for the ocean

I hope this information helps