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Troubleshooting: Flocculator Agitator Gearbox damage, Temporary Fix?

We have a 300 KLD continuous flow ETP plant. Recently, the flocculator agitator gearbox got damaged and we had to continue with the working of the plant. As a temporary measure, we fixed a 3HP pump to circulate the water in the Flocculator tank but this method was not that efficient.

We also tried agitation with compressed air and even that did not work well. Can anybody suggest us a better method so that we can manage till the gearbox is repaired. The flocculator tank has a capacity of 60m3.

Guru Dutt K V,




Dear Mr. Guru Dutt K V,

Flocculation is a process where the flocculant bring the particles together to form the floc that can settle easily. The size of a flocculator to be very large, it seems that you may be handling the sludge in the flocculator.

The control aeration with the properly located diffuser at the bottom can serve the purpose. It may be noted that any vibrant agitation will not form the floc.

You can use the pump with multiple inlets fix on the walls that can cause the mind turbulence, which can bring the particles together. This totally depend on trial and error method.

Putting the baffles depend on the geometry of tank this may or may not help.

Since design specification are not available it difficult to recommend the appropriate method.

We can help you to design alternative if the detail specification and drawing are made available.

Prof. R. V. Saraf
21, Radhakrishna, Near S.B.I., Paud Road, Pune 38
Mobile: 020 25433445
Web: http://www.


I’m very surprising you have such a large flocculator, but you can go for baffle chamber for flocculation but the HTR should not more than 15 to 20 min, baffle chamber have own advantage , not required any power, moving parts, operating cost is nil , you can try this method for your plant


Dear Guru Dutt K.V,

The compressed air can do more damage if it is applied with high pressure or without proper diffusion. For a tank of 60 cum, the probable size must be 2 m liquid depth and some 5.5 m * 5.5 m in plan. The pressure at the air release point must be just about 2.5 m water column or 0.25 kg / sqcm. In addition, they must procure a good air diffuser membrane from suppliers and connect it and then add a weight to it and leave it on the floor.

Best is to call up a standards supplier. This arrangement can also be kept as a spare for the future. Alternatively, increase the dose of polyelectrolyte in flash mixer and let the flocs settle in flocculator itself and bleed from flocculator. In an ETP, I will prefer the latter choice.

Thanks & Regards

Technical Advisor (ex-Engineering Director of Chennai Metropolitan Water Supply and Sewerage Board)
Creative Environmental Consultants
Chennai, Madras


Dear Guru Dutt K V,

It is but natural a normal pump would not work as it will get clogged due to the suspended matter and slurry in the tank.

What could work is if you used a 5 hp sewage pump which has a open impeller and has a solid handling capacity up to 15mm.

More over the discharge of such a pump is also very high and would help in circulating the sludge within the tank.

The only problem i see in this is that the suction pipe would be stationary there is bound to be sedimentation where the suction effect of the pipe ends.

To ensure that the sediments are uniformly sucked up and kept in suspension, the suction pipe will have to be manually moved from time to time. ( say at 15 min to 30 minute intervals)

Or one could think of the suction pipe being fitted with something that could facilitate suction over a broad area like the system used in manual cleaning of swimming pools , but this also involves moving the suction pipe manually all over within the tank area.

I hope that it works as well as I think it will..

Anil Lalwani
Well & Water Works, Pune


Dear Guru Dutt K. V,

It is most surprising you have such a large flocculator. I suppose your particular effluent may demand it - normally the retention is just around 15 to 20 minutes.
You can put in a number of vertical partitions / baffles for static mixing. This should work very well.


Keshav Agarwal
Technical Consultant
Biotech Services
Noida, UP


Dear Guru Dutt K.V,

First of all, I do not think that the flocculator tank shall be 60 cum volume. This is because for a plant of 300 cum/day, the capacity of flocculation shall be about 6 cum. The plant is of either 3000 cum/day or the tank for flocculation is 6 cum volume.

Either way, we suggest you to go in for a flocculation tank having baffles to ensure flow of water in a way that aids flocculation. A flocculation tank of detention time 15 minutes of average flow having baffled passage shall be sufficient for the purpose. Even after the flocculation gear drive is rectified, it is not necessary to use the same.

With best regards,

Taral Kumar
Executive Director
Akar Impex Pvt. Ltd.
Noida, Uttar Pradesh

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