A DEEP BAR SCREEN IN BOMBAY

Regular readers of this Blog will by now know that the “Bar Screen” is the first unit in any STP, which captures Solid particles above a certain Size, and prevents them from entering the STP, thereby saving a lot of grief : they save the pumps from getting clogged/ choked.  They save submersible pumps ( wrongly selected by plumbing engineers moonlighting as environmental consultants, and ignorant vendors for raw sewage lifting applications) from breaking down with regular frequency, and most important of all, permit the STP operator to concentrate on other aspects of the STP, instead of spending his entire life battling solids in the raw sewage pumps.

Believe me folks, this is THE MOST VALUE FOR MONEY piece of equipment in the entire STP.

I should like to illustrate this from a real life experience of mine from about 30 years ago, when the Bombay Municipal Corporation decided to install for the first time, bar screens in its incoming sewer lines deep beneath Ground level.

I had just got back from the US carrying my freshly minted PhD Certificate, landing in Santa Cruz airport, Bombay on the 31^st of Dec. 1978.  ( I have a poor head for all other dates).  Sometime in early February, 1979, I started my career as a “Trainee Environmental Engineer” at a princely salary of Rs. 750 a month,  in the most venerable of Companies in the Environmental field : Dorr- Oliver (India) Pvt. Ltd., a wholly owned subsidiary of Dorr - Oliver Inc., Stamford, Connecticut, USA.

I had an equally venerable Boss by name Natarajan, a battle hardened veteran of many an illustrious sales Conquest, and a legend in his own time : a jolly, affable, roly poly kind of bloke,  he was the Asst. manager in the Env. Engg. Division.  Don’t let the designation fool you : US companies in those days were extremely niggardly in doling out labels.  An asst. Manager was fairly high up in the hierarchy of the Company and held quite a senior, responsible and accountable position : A “Manager” in that Company was indeed the Cat’s whiskers, and a “General Manager”  ran the entire Company.  Very unlike present day designations where a fresher right out of college,  starts off as an Asst. Vice President in a multinational Bank.

In the year 1980, The Bombay Municipal Corporation ( BMC) was the happy recipient of a huge sum of money as USAID to improve and upgrade its Sewage Treatment Plants at various locations across the city.  Not surprisingly, the aid came tied with a US Consulting Company called Engineering Sciences Inc. ( ES).  Very wisely, the BMC decided to install Bar screens in all their STP’s as the first order of business.  Dorr- Oliver India was the favourite to bag these contracts, being a true Blue American Company.

Municipal sewer lines, due to the very long distances of travel, arrive at the STP location at great depth, at times  30 feet or deeper below Ground level,  very much like in several Sobha projects in Bellandur ( although in the latter case, the situation may be attributed to third rate plumbing consultants *** employed to design and engineer the STP).  Now, a municipal sewer line can carry solids and other gross articles of varying size and description.  The great depth, the huge volume of sewage flows in these pipelines, and the quantity of solids that can accumulate in a very short period of time, make it imperative that mechanical means be employed to clear the screens on a continuous 24 hours basis : Hence the concept, design, and a marvel of engineering called a “Mechanical Deep Bar Screen”. 

A Mechanical deep bar screen is a device which employs reciprocating motion, going up and down, up and down.  At the bottom of the downward stroke, the fingers of the rake mechanism engage with the openings in the stationary screen rack, pick up all the solids deposited on the surface of the screen and haul them upwards along the inclined screen.  At the top of the up stroke, a tipping device helps disgorge all the solids thus transported directly onto trucks stationed below, to cart away the solids, when fully loaded.

Dorr- Oliver having put in its bid to supply these sophisticated Bar screens to the BMC, was called by the American consultant to present our case and highlight the special and unique features of our screens.  ES was represented by a young fellow by name Chip Woltz :  Dorr - Oliver by Natarajan, and yours truly, as an apprentice in training, with strict instructions to keep my mouth shut and eyes and ears open during the proceedings.

When asked to specify the kind of solids or articles our Bar screens could handle, Natarajan puffed out his chest and pompously proclaimed “ Sir, in Bombay, we even get dead bodies in our sewer lines.  Our screens are designed to handle such heavy loads, hahaha ”

Chipper Woltz, though young of age, was clearly upto this Indian game of one-upmanship :  Says he  “ In our country we get discarded refrigerators and Volkswagen Beetles in our sewer lines : tell me, can your screens handle these ? “

For once, the irrepressible Natarajan was utterly dumbstruck

Dr. Ananth S Kodavasal                                                                          April 23, 2011

Ecotech

*** POST SCRIPT ON THIRD RATE CONSULTANTS

During my School days, my father being in a transferable job, was obliged to move from city to city every few years.  Not to inconvenience us kids, my sister and I were left in the care of my grandparents in Madras.

On many a Saturday, when school was off, I loved to accompany my granddad to his office, taking the bus from Hamilton Bridge in Mylapore to Parrys Corner.  From Parrys Corner, we had to walk down quaintly named streets such as Thambu Chetty Street, Linghi Chetty Street to where his office was situated.

These streets were lined on both sides with small business enterprises dealing in engineering goods, machinery and parts, with sign boards proudly proclaiming to be “Mfrs. Representatives and Commission Agents “.

Likewise, I wish Third rate consultants in Bangalore ( of them there are many) would call themselves with such names as  “ XYZ Commission Agents and Plumbing Consultants” so that nobody is left guessing as to where their priorities and loyalties lay.

ASK