Very Rough Feasibility of a prospective village sewage treatment plant

[tj00889]

Hey Guys,
I would like to know from some of the more experienced engineers out there how you would go about ball-pointing the feasibility of a sewage treatment plant at the get go. In other words ,before anyone decides to spend any money on a thorough feasibility study. Namely ,I'm interested in bare minimum space requirements (rough cost) for say sewage treatment of a 10,000 population town for reuse in irrigation .I know there are many factors at play here but I'm speaking in very general terms .
Any input would be appreciated and stating some helpful resources would also be appreciated.

 

[256bits]

The first thing you would have to do is estimate the amount of fluid that the town of 10,000 will produce.
And add to that how much precipitation there is for the location and how much of that enters the sewage system to go to the treatment plant instead of soaking up into the ground. You could use a holding facility for this precipitation since it is sporadic ( and the resident fluid ), or else let it overflow into the surrounding area, lake or river in times when it is excessive ( would that be one or more times per year you and your town will have to decide, along with the regulations required by higher levels of government ).

For the actual treatment, I suppose you will have to investigate how that is done and base the size of facility on volume of fluid that can be processed on a rate basis.

 

[Mordred]

Along with the information already provided you also need to consider tank size for the flocculant to bind to the waste. The flocculant lifts the waste material to be scraped off the surface as well as having scrapers below. Flocculants are specific to the chemicals used, and require specific PH control. So acids are also used, commonly sulpheric acid. Settling times on systems I've worked on are usually 1 hour. Then the water must be stored long enough to balance the BOD. (Bio oxygen demand). The settling time for the flocculant needs to be long enough for the flocculant otherwise your total suspended solid count will be high (TSS). Precise PH control is to say the least extremely tricky so the tank used for acid injection must have adequate stirring, even then precise control is near impossible. Part of your cost will need to include what to do with the waste derived via the flocculant, as human waste is poisonous to the environment. Waste from herbivores can be used for fertilizer, however you cannot do the same for carnivore or omnivore waste. (meat eaters).

Your best bet is to look for a chemical company that designs the flocculant for waste water facilities, and find out what their chemical cost is, settling time requirements, and PH requirements are. Different flocculants require different PH levels etc.

Also filters and membranes are used to remove the majority of the solids, so you also need to consider what to do with the solids such as plastic, metal, wood and cleaning chemicals that people tend to flush down sewage systems.

For resources I would talk to other sewage treatment plants already in use, as different Countries have different sewage treatment requirements on TSS and BOD levels etc