An ETP wall of foam

March 15, 2018


During my graduate studies at Vanderbilt, I visited the Country Music Hall of Fame in Nashville, Tennessee. This story is about the time I inadvertently walked into a Wall of Foam at an ETP (Effluent Treatment Plant). 


I moved to Bangalore from Bombay in the year 1986, after quitting Voltas International. I found temporary accommodation in Bangalore for the family and myself on Charles Campbell Road in Cox Town. Quite by accident one day, I bumped into an old colleague of mine from Dorr-Oliver now settled in the very same neighbourhood. B. Velan was a brilliant mechanical engineer, and headed the engineering and drawing operations of Dorr-Oliver in the Madras office. After quitting Dorr-Oliver, he set up Scorpio Engineering in Bangalore, manufacturing bulk material handling systems and equipments.  


With active encouragement from Venkataraman (RIP) another old colleague of mine from Voltas, based in Madras, Velan ventured into wastewater treatment, banking on his past experience in Dorr-Oliver and Venkat’s process and design expertise. Little did he realise the pitfalls in the business. They had managed to bag an order for an ETP at Mysore Acetate and Chemicals (MACC) a particularly complex wastewater, and had completed erection of the plant when I walked into their parlour and was roped in to startup, stabilize, and commission the treatment plant. This was possibly one of the first assignments for Ecotech in Bangalore in the year 1987.


The Mysore Acetate and Chemicals Ltd. is one of the oldest industrial undertakings of the Govt. of Karnataka, now defunct and boarded up. MACC is located in a place very imaginatively named Acetate Town, on the outskirts of the equally drab and unimpressive town of Mandya in the South Eastern part of the State. MACC produced Cellulose Triacetate and related products used for making tooth brush handles, TV cabinets, photo film and so forth from cellulosic materials such as cotton, wood chips and wood pulp.  In the main, two streams of process waste were generated from the operations, the one called black liquor and the other the high COD (organic content)  stream.  The two streams were segregated at source and in the ETP, received separate and different treatment.


Velan the master had excelled himself. In this project insofar as of some of the mechanical equipments he designed: Instead of circular clarifiers, there were rectangular clarifiers (highly space efficient) with the bridge moving up and down along rail tracks, fitted with limit and reversing switches at both extremities, much like overhead traveling cranes. I was fairly comfortable with this design having previously commissioned such units at the Dudeshwar Water Treatment pant for the Ahmedabad Municipal Corporation about 5 years previously.


At the exit end of the treatment plant, in order to collect a composite sample of  treated water (as opposed to a grab sample)  there was a Ferris wheel like contraption going round and round, picking up a smidgeon of a sample of the water at every rotation and depositing it in a compositing bottle placed alongside. The speed of the Ferris wheel could be varied at will by the simple device of turning a screw. The aeration tanks in the treatment plant were however outfitted with High Speed Floating Aerators, which were not entirely to my liking.


The fault lay however in the design of the treatment plant.


The usually meticulous and diligent Venkataraman had slipped up in the design. He did later confess to me that in their hurry to put in the tender, he had not made a detailed independent study of the effluent characteristics, nor validated the figures specified by MACC:  The High COD stream indeed lived up to its name. But instead of the design value of 3000 mg/L of COD, in reality it turned out to be in the range of around 10,000 mg/L, when I was commissioning the treatment plant. This high COD stream was absolutely clear, colourlesss and odourless much like the bottled mineral water of today, and would deceive any person at first glance.


The very refractory black liquor stream also was very difficult to stabilize because of the high speed floating aerators which were simply shearing and pulverizing the bacterial flocs and not allowing them to settle in the clarifier.  


Although we could demonstrate good performance of the ETP in terms of pollutant removals in absolute terms (Kg COD/ day), we could not achieve the low concentration levels (mg/L ) on account of the wrong design figures supplied by MACC. The clients too reconciled themselves to this fate, albeit with some reluctance.


I had posted a chemist full time at MACC to supervise the commissioning of the ETP, and I made fortnightly visits from Bangalore to monitor the progress and give necessary guiding instructions.


It was a cold, cold morning in December, when Nagaraj (the MACC Chemical engineer in charge of the ETP) and I walked towards the ETP a little distance away from the main factory. The ETP was now hidden from view by a 12 foot high wall, apparently a new construction, not there on my previous visit, neatly whitewashed and shining bright against the winter sun.  Lumbering towards the Wall and the ETP on that cold winter morning,  I expressed my surprise to Nagaraj that a government-owned unit could put up such a huge construction in such a short period of time.


And that was when I walked into a Wall of Foam. For a few moments I was absolutely stunned when I discovered the wall to be entirely made up of thick white foam, churned up by the high speed aerators, bobbing forlornly in the middle of the aeration tank, trapped within the four walls of foam.




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