rural facultative pond capacity

Question

rural facultative pond capacity

smillar (Civil/Environmental)

(OP)

25 Jan 03 20:26

I have to rate the capacity of a rural facultative pond (2 cells in parallel)to see if it can sustain the projected pop'n growth over the next 10yrs.
Known:pond vol.,Qinf & water quality in (both from metered force main),water quality out, source of hauler waste (res. septic&holding tanks)
Estimated:Qeff, vol. of septage contributed by haulers, det. time (they're discharged twice a yr)
Assumed: d=0.5, k(20deg)=0.25, theta=1.06
Unknown:liquid temps, quality of hauler waste
Originally I planned to back out seasonal k values given that I knew BOD in and out for existing conditions, and then proceed with the projected flows to see what vol. of pond I would need for the same performance (BOD removal). But, then I realized I couldn't account for the hauler waste BOD - so I don't really have So/S.
Are the above noted assumptions reasonable and would it be practical to assume hauler waste BOD (from Metcalf&Eddy)and perhaps even rate constants knowing typical ambient air temps? (especially given that even Qeff is an estimate)
Thanks in advance for any suggestions.

DavidCavender (Civil/Environmental) · Answer 1 · 2003-01-26 16:47:30

Sounds like you are on the right course to me. Regarding the temperature input, remember it is for BOD5 reduction which decreases with decreasing temperature, so winter removal efficency controls the effluent quality.

I would be comfortable using literature values for the hauled waste only if it is predominatly residential. If it is industrial and commercial, you shuld do some testing. There is lots of high strength and toxic waste out there.

KRSServices (Civil/Environmental) · Answer 2 · 2003-01-30 17:50:42

Determining BOD on hauled waste is a bearcat. I've had residential hauling from systems that "shocked" my treatment facility, particularly in winter. The remedy was to introduce starter enzyme (acti-zyme) bacteria to get the system functioning normally again. Haulers should be septage haulers only, and not crossovers with other industries (such as oil patch or industrial). If they serve other clients, then verification has to be submitted that the tank was flushed properly before picking up septage. Again, I had an oil hauler sneak a septage load without first flushing his tank. THe result was a nasty cleanup bill for removal of the oil plus loss of his license to dump. He was also turfed as an oil hauler due to the Provincial regulators getting on the oil company's case. Be careful.

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rural facultative pond capacity