For every single system I’ve ...

For every single system I’ve ever designed (20+ systems) I agree 100% with the last poster that it depends on the experience of the engineer. There is no “one size fits all” solution that will solve your problem (man do i wish there was!!!).  The very basics are building blocks and foundation to a successful solution which are:

- budget (if there was never a budget issue I would almost always choose a Bioalc or some type of biological nutritent removal system...but they can be covert costly....even an old technology like an oxidation ditch is incredibly efficient at reducing the regulated parameters....at least where I live)

- is the treated effluent going to be deep well injected, remain on the land for evaporation, or discharged to a surface water body.  If a surface water body is it fishing bearing or not and what is downstream of tbe discharge point

- what are the regualted parameters that the treated effluent  must meet I your region

- how much land space is available to you 

- do you have a mixture of regular city wastewater or do you have industrial wastewater as well?  For example, where I live we had to design the entire system around the fact that we had a beef and a pork rendering plant which resulted in ridiculously high BOD levels (3 to 5 times that of regular city wastewater)

- if there is any fish rendering plants or vegetable process like a pea processor that goes into the city’s wastewater system be INCREDIBLY careful as the BOD for a fish plant we have found (and I am not exaggerating at all) was In the 10,000 ppm!!!!!!!!!

- is there chlorine injection and then removal in the final treated wastewater 

- does the town want a “green solution”

- what are the levels of the basic parameters such as N, P, K, ammonia, and unionized ammonia (very very important for fish)

- are you required to do a downstream impact study

- will the treated wastewater pass the T50 trout mortality test

Tbe list actually is longer than just this but it gives you an idea of how complex wastewater treatment is. Like the others have said, contact a number of vendors and give them the parameters they ask for and start there.  And remember....we are always here to help you!!!!

Sincerely,

Kurt Rasmussen, P.Eng.