CEE 371


Fall 2009

Homework #8   Wastewater Characteristics & Sewer Hydraulics


1.      A municipal wastewater treatment plant receives a seasonal discharge from a fruit processing company.  Influent flows to the municipal wastewater treatment plant and wastewater concentrations when the company operates and when it is not in operation are shown in the table.  Note that these are total values which include sanitary WW and industrial WW.


Municipal Wastewater Flows and Concentrations



Company Operating

Company Not Operating

Flow (m3/d)



BOD5 (mg/L)



SS (mg/L)



NH3 as N (mg/L)



Cl- (mg/L)



Alkalinity (mg/L as CaCO3)




Determine the contribution (or loading) of each wastewater constituent in both kg/day and lb/day for both cases of the company in operation and when it is not operating.  Also, determine the flow and constituent concentrations for the fruit processing wastewater by mass balance analysis (assume all parameters behave conservatively). 


2.                  A town has a population of 7500 and a domestic per capita wastewater flow of 100 gpcd. The municipal wastewater plant receives the domestic flow and industrial wastewater discharges of 65,000 gpd from a cheese processing plant and 90,000 gpd from a brewery. The BOD loads of the domestic wastewater and brewery wastes are 0.20 lbs/cap-day and 450 lb/day, respectively.  The BOD concentration of the cheese wastewater is 1400 mg/L.  Calculate the total (domestic plus industrial) wastewater flow in MGD, the BOD in mg/L of the total wastewater, and the BOD equivalent population for the total wastewater.  


3.                  What is the flowing full capacity (Q, in gpm) and velocity (V, in ft/s) for a 12 inch diameter sewer at a slope of 0.0060 ft/ft for:  a) Manning’s n of 0.013 and,  b) n of 0.011?


4.                  Use the pipe flow graphic reproduced below (from Viessman & Hammer text; Figure 6.2 or 7.2 depending on edition) to answer the following.  A 33 inch sewer is placed on a slope of 0.40 ft/100 ft.  Manning’s n is 0.013.

a) At what depth of flow is the velocity equal to 2.0 ft/sec?  

b) If the depth of flow is 18 in, what is the flow rate? (in gpm). 




Assigned: 30 Nov 09

Due: 7 Dec 09


extra fig 2.jpg