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Saravanan

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Sewage Treatment Plant
Jul 05^th, 2012, 10:01pm

Good Day All. I have a limited knowledge upon Sewage Treatment Plants. Currently I am monitoring the flow of incoming raw sewage by using a magnetic flowmeter (Promag to be exact), for the flow of 20 cu.m/hr (pump capacity), a DN50 size flowmeter was recommended. But right now the flowmeter shows a flow of 0.207 cu.m/hr. Is it that I had chose a wrong type of flowmeter? Take note that the pump is a grinder type.

Another problem is, last week I took a sample of the incoming raw sewage and sent it for analysis. The analysis shows a pH of 2.9 and COD value at 1500 ppm. Its rather abnormal for that plant since usually I will get COD at 350ppm and pH at 6.7 to 6.9. We do have kitchen and laundry waste entering into the plant. I appreciate if anyone can give an explanation on these two matters. Thanks and God bless!

Regards,
Saravanan @ Logan

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Jeff Naumann God Member Offline I love Water and Wastewater.com Posts: 1133 Torrance, California Gender: Company or Organization: Jeff Naumann & Associates	Re: Sewage Treatment Plant Reply #1 - Jul 6^th, 2012, 7:34am Are you sure that the flow meter was properly installed? Was the meter properly calibrated? Is the pipe always "full?" A mag meter will not work if the pipe is not completely full.
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JB YaBB Newbies Offline I love Water and Wastewater.com Posts: 29 Hyderabad Gender: Company or Organization: Water Projects India	Re: Sewage Treatment Plant Reply #2 - Jul 6^th, 2012, 11:32am Dear Saravanan Helo Check the values after recalibration of both the pH and flow meter, then let us know if the problem exists any more. regards JB
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Saravanan YaBB Newbies Offline Water and Wastewater.com, the power portal!! Posts: 13 Gender: Company or Organization: Nalco Industrial Services	Re: Sewage Treatment Plant Reply #3 - Jul 8^th, 2012, 8:27pm Good Day Jeff, The pH meter and flowmeter is calibrated and the pipe is full. Pump discharge pipe size ia at 4" and reduced to 2" for the flowmeter. Does the reduction may caused the increment of flow, as per the hydraulic calculation Q₁A₁ = Q₂A₂?
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Jeff Naumann

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Re: Sewage Treatment Plant
Reply #4 - Jul 8^th, 2012, 9:15pm

Saravanan wrote on Jul 8^th, 2012, 8:27pm:

Good Day Jeff,

The pH meter and flowmeter is calibrated and the pipe is full. Pump discharge pipe size ia at 4" and reduced to 2" for the flowmeter. Does the reduction may caused the increment of flow, as per the hydraulic calculation Q₁A₁ = Q₂A₂?

Actually, since flow through both sections of the pipe is the same, Q1 = Q2; and Q = A x V; or, (A1 x V1) = (A2 x V2)

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Anabaena

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Re: Sewage Treatment Plant
Reply #5 - Jul 8^th, 2012, 9:17pm

Saravanan, We also have had this issue. Is the waste stream high in solids and fouling the nodes on the inside of the flow meter? Is it possible the meter is oversized? It looks like the specifications on the meter would be ok but if the velocity is low we have encountered this same problem and had to downsize the meter. This may not be the cause of the problem in your case. Does the manufacturer have any suggestions? Please keep us informed. I hope this helps.
David

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Saravanan

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Re: Sewage Treatment Plant
Reply #6 - Jul 8^th, 2012, 9:45pm

David,

The flowmeter was sized by the vendor themselves, who recommended 2" flowmeter for a flow of 20 cu.m/hr. I may say that the waste contains a moderate amount of solids. The pump we use here is a submersible pump with a grinder head, which grinds the large solids into smaller solids. I am still talking to the pump and the flowmeter vendor regarding this and will update soon. Thanks.

Regards,
Saravanan @ Logan

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