×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Sewer Flows mimimum lpcd

Sewer Flows mimimum lpcd

Sewer Flows mimimum lpcd

(OP)
We have a World Bank project to rehabilitate/improve water supply and wastewater to 7 towns in a developing country. The Client has aspirations of piped water and main sewer systems. Current water consumption is as low as 20 lpcd. (litres per capita per day). Limited resources mean that even after rehabilitation supply is unlikely to exceed 50 lpcd. It is suggested for a self cleansing foul sewer system a reliable water supply and a minimum consumption of 100 lcpd are basic requirements (WHO).

I am looking for any guidance, references, papers etc. on minimum foul sewer inflows to give relative maintenance free self cleansing operation.

RE: Sewer Flows mimimum lpcd

For self-cleansing, the system must reach a minimum scour velocity of 2 fps during peak inflow.

The 20 lpcd is probably an average inflow rate, use that to design treatment facilities, not conveyance.

Use Qpeak for conveyance, apply a PF between 1 to 4.5, depending on population, usually between 3 and 4.  This takes the Qdesign to 60-80 litres.

But even using the 20 lpcd, the system might work.  If the system is designed for 100 lpcd capacity, but only achieves 20 lpcd inflow, v/vf will be about 0.78.  As long as v at Q/Qf is 2 fps or greater, the system should scour.

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

RE: Sewer Flows mimimum lpcd

(OP)
Iha thanks for your reply but perhaps I have not explained my problem. The concern is not the self cleansing velocity but how much liquid is needed to move the solids. The following is a quotation from a WHO conference on water and wastewater management in 2001. - The flow of 100 Lpcd appears high to me ??

- "Conventional sewerage systems are designed as waste transportation systems in which water is used as the transportation medium. Reliable water supply and a consumption of 100 Lpcd are basic requirements for problem free operation of conventional sewerage systems" - .

With a supply of only 20 Lpcd (5 gals/day/capita) waste would comprise practically only solids.
#
cheers

RE: Sewer Flows mimimum lpcd

You are describing an aspiration that most people have, but that is probably unaffordable for your client. The lack of sufficient and reliable water supply (and/or power supply) will probably preclude the use of the system that is proposed.

You probably want to investigate the Shallow Sewerage system. A toilet, usually in-house, flushed using lower volumes of water than either conventional sewerage or septic tanks, to smaller diameter sewers laid at flatter gradients and shallower depths between dwellings on a block. On-site shallow inspection chambers are also provided.

Look at the South Africa examples here:
http://web.mit.edu/urbanupgrading/waterandsanitation/levels/provide-san-serv.html

http://www.dwaf.gov.za/dir_ws/content/lids/PDF/Technical.pdf

RE: Sewer Flows mimimum lpcd

(OP)
bmr thanks for youir reply  

1) You are correct the project is not financially sustainable but the client does not understand. The World Bank are dumping money on non sustainabale projects!.

2) Septic tanks and small bore effluent piping is a good technical solution.
- thanks for the links

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources