SSA Diurnal Wastewater Hydrograph

[Anonymous]

Where does the diurnal hydrograph for typical residential wastewater flows in SSA come from? I see it used often but I can't find any scientific journals justifying how it is created. I understand the logic behind it, but am looking for the specific journal citation to justify its use.  Thanks for your help. 

[Anonymous]

Bump

[wfberry]

Here is a link to a journal report.  Since my knowledge of a Diurnal Hydrograph is limited to just what I learned today, I hardly see any connection to your attached hydrograph.

Bill

http://snr.unl.edu/szilagyi/jh10.pdf

[Anonymous]

Thank you for your response. The diurnal hydrograph I am refering to is specifically for estimated wastewater flows for development. Not for stormwater/groundwater as your journal article linked.  

SSA has a "default" sanitary time pattern that is in their models, modeling the AM and PM peaks of a normal wastewater system (caused from workers waking up in AM and chores in PM). I've seen this same pattern all over, but I want to know how it is derived or justified. See my clipped image from one of SSA's own sample models using this hydrograph pattern for WW inflows. 

Thanks

[nate.philbrick · Accepted solution]

Hi @Anonymous , 

Thank you for reaching out in the Autodesk forums. This is a great platform where you and the rest of the Autodesk community can benefit. This is a generic hydrograph making estimated peaking factors in the morning and evening for residental wastewater flow. There is not a specific study where this has been derived from. You can adjust your inputs for higher accuracy. For sanitary sewer design, I have always computed the average daily flow and multiplied by a peaking factor (and then add any additional flows for I&I). 

Please hit accept solution if this answers your question. 

[Anonymous]

Thanks for your response Nate. I also usually size WW lines to the hourly peak which is a multiple of the daily peak calculated from the local municipality's design manual (plus I&I). In this situation though we are hoping to utilize this information to design a private WW equalization tank for a development to discharge into an overloaded city system during non-peak times. This requires the entire hydrograph for the system (and not just the peak) so we can properly design detention volumes. I will accept your answer, but it's a little disheartening to hear that the "generic" hydrograph doesn't have a justification to it. I don't fault Autodesk as it seems that everyone is using a similar graph, but as engineers we like to think that everything that we do has a basis behind it.