Sewer Storage Structure

[PNGENG]

Hi Guys,

I have a subdivision project which is just outside of a city. We unfortunately just found out that the main sewer networks that serve the city do not extend outside to this particular area. So the client has instructed us to design a temporary sewer storage well that wouldn't take up too much horizontal space and would only require a pump out once in 6 months.

Note that there are more than 100 lots in this subdivision and it is in a developing country located in the tropics with predominantly wet and hot weather all year round. We have ruled out construction of sewer lagoons due to it being not practical, unavailability of land space, risk of inadequate treatment before discharging into natural watercourse and breeding of mosquitoes. Also, the client prefers a sewer network rather than stand-alone septic tanks.

Is it even possible to construct a reliable and lasting storage well? If so, what are some of the very important factors that need to be considered?

 

[stanier]

There are available bladder type storage tanks that can be laid on ground. The number of tanks depends on your total volume to be stored. These will require land though Also you could expect gas generation to occur as the sewage goes septic.

You could use the Mono Pumps individual tank and pump with a network of PE pipes to gather the sewage at the bladder tanks or a centralised treatment facility.

http://www.monopumps.com.au/en-au/packaged-systems

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http://waterhammer.hopout.com.au/

 

[bimr]

Don't think you will be allowed to put raw sewage in any type of well.

 

[77JQX]

Do I understand this right? The client wants to store raw sewage for 6 months? And have it "not take up too much space?" And then pump it out? Into what?

If this was in the US, I'd figure on 100 gallons of sewage per capita per day. For your 100 unit subdivision, that would amount to 25,000 gallons of sewage per day (with an average of 2.5 people per unit) - enough for more than six 4,000 gallon trucks per day. I don't think pumping into trucks is feasible, and don't see why storing sewage for 6 months is desirable.

I think your client needs to extend the sewer to his subdivision, or build his own treatment facility.

 

[rconner]

As others have noted, you are in kind of a Brave New World with this suggestion (as most guidance I think you would see in the sewer world suggests minimizing sewage "retention" time prior to treatment!) I don't know exactly what one would have if you put raw sewage in particularly any sort of closed off container for six months(and not really sure I would want to be there for the unveiling after that amount of time to find out! - see e.g. guidance at

http://en.wikipedia.org/wiki/Cesspit

for any sealed "holding tanks") However, I think/guess that after only a couple days or so in any large container you would at the very least probably have some notable segregation of the solids and unmentionables within same (there would be much more viscous layers formed from the "floaters" and "sinkers"). How to deal with same, as well as safety and other issues with hydrogen sulfide, other gases and who knows what else etc , remotely or in the field might indeed require some serious thought.

 

[bimr]

Not sure where you are located. We usually assume that each residence holds 3.5 people equivalent.

If you assume a flow of 30 gpd per person or 105 gallons per household per day, you can probably transport this volume by tank truck.