Emergency Storage of Sanitary Sewage? 1

[Dunz]

We have been asked by a client to start gathering information on methods of storing sanitary sewage on-site in case of an emergency. They have asked for the ability to store up to 7 days worth of sewage.

As an initial estimate we have gathered water usages records for 2 years and their monthly water usage averages at roughly 5 Mgal during average months and 7 Mgal during peak months. Their existing sanitary sewer system discharges to the City’s collection system at several different locations by a combination of gravity lines and sanitary lift stations/force mains. We have since begun breaking down their existing sewer system into individual networks and begun to estimate the amount of sewage each network produces, based on these initial estimates the storage volumes for the requested 7 days range from 16,000 gal for the smallest network to as much as 430,000 gal for the largest network.

I am seeking advice on where I can begin gathering information on viable storage methods and any relevant national standards. We already started looking at both underground and above ground storage tanks. Has anyone been involved in a similar project? Does anyone know of a good reference book(s) or a similar project(s)?

Thanks in advance for your time any advice is greatly appreciated.

 

[bimr]

Emergency storage is another name for equalization tank.

You would use any type of tank that you desire for this storage.

You have to have some type of provisions to clean the tank out after use since the remaining sediment in the tank will smell.

You may have to add mixing and aeration depending on how long that you are holding the wastes and the tank arrangement.

 

[semo]

I agree with BIMR.

This is the same as equalization.

Other considerations along with his include:

Is this tank in series with the City's lines or parallel. Basically I mean will all of the flow run through this tank or will you take a portion of your flow to the tank.

How you will fill and drain the tank (gravity fill/pump drain, vice versa, gravity fill/gravity drain, etc.)

What about grit removal and floaters. If you don't remove it up front, you will have to clean it out of your storage at some point

What capacity is the City's main? You can't exceed that when you drain the tank back to the system.

10 states standards have some design requirements. Another good resource for consideration is Metcalf & Eddy.

 

[civilperson]

Sewerage lagoons are able to do dual purpose, storage and treatment. They are cost effective if land is available.

 

[bimr]

Here is a cleaning device for a storage basin:

http://www.gnacso.com/SELF.htm

 

[coloeng]

Another thing that needs to be considered is the increase in flow due to infiltration from ground water or a storm event. This can increase the size of the storage significantly.

 

[stanier]

In Sydney the Northside Storage Tunnel was constructed. This was aimed at storing the wet weather flows from storm events. Overflows into Sydney harbour were rpevented. The stored volume was then processed at the North Head Sewage Treatment Works prior to discharge through a deep water ocean outfall several kilometres out at sea.

The tunnel duplicate the main carrier and was large enough to store the flow.

http://www.sydneywater.com.au/OurSystemsAndOperations/WastewaterSystems/NorthsideStorageTunnel/