Last week I had posted an article on the Design defects of a FAB reactor in Electronics city : such was the enormity of Engineering defects in that plant that it would make any self respecting engineer turn over in his grave. What is even more shocking is that this abominable article of design and engineering could pass muster with a number of intermediary agencies : The project team of the client - Architect - Structural designer - KSPCB etc. Well, less said the better. Although a little lacking in sophistication, I am attaching hand drawn sketches of this monument, built I am sure with excess of cement and steel, still standing but defunct like the old Roman Aqueduct in Segovia, Spain.
35. HOW NOT TO ENGINEER A TREATMENT PLANT
A previous article in this Adda/ Blog had a case study of a treatment plant in Electronics City , Bangalore with the fancy acronym #@&%, sold to a software major by Zermatt . Now Zermatt is a water treatment company and should stick to their core competencies, instead of dabbling also in wastewater treatment. Wastewater treatment is an Art, but most certainly not that of an Artful Salesman.
I touched upon only the contradictions, deficiencies and defects in the Design of that treatment plant in the earlier essay. In order to fully appreciate the extent of technical bankruptcy of Zermatt I must describe the Engineering aspects of the #@&% Plant in Electronics city, and the reasons why I refused to take over the pant for operation and maintenance.
Pls. refer to sketches attached of the plant. The deficiencies and defects in engineering pointed out by me, which would vitiate all efforts towards proper Operation and mtce. of the plant were :
1. The Bar screen and Bar screen chamber were constructed along the retaining tank wall : There was no way to access the screen, since no approachway was provided. The Bar screen therefore was only an ornamental piece of equipment in the STP.
2. The Equalisation tank was also constructed as a free standing tank. No approach ladder/ operating platform was provided for regular monitoring and maintenance.
3. Two Nos. Air blowers were mounted on a tall pedestal structure ! I am totally at a loss to fathom this piece of engineering sophistication. Neither was a ladder provided to approach the blowers, nor was there sufficient working space around the blowers on the pedestal to carry out even routine maintenance activities like topping up of oil, replacing V belts etc.
4. The FAB reactor being a tall column, the secondary settling tank following it had to be at an elevation, supported by MS staging. Even here, no access was provided to the top of the plate settler, unless the client chose to employ monkeys to operate the plant.
5. Plate or Tube settlers are not recommended for use in secondary settling of mixed liquor from a biological aeration unit. Also, due to very short residence times in the plate settlers, the underflow sludge is very thin, necessitating further thickening/ conditioning of sludge and overall greater difficulty in sludge handling and disposal.
(Though most commonly used for primary clarification, these units can also be effective in decreasing the MLSS (mixed liquor suspended solids) entering secondary settling tanks when located at the entrance to the secondary settling tank or at the end of the aeration tanks.
Thus, plate settlers are not recommended even by manufacturers to be the sole and only settling units for biological sludge : at best they may be used as a presettler before a conventional clarifier.
6. The Backwash waste from the Pressure sand filter and Activated carbon filter were simply let out on to the floor of the STP retaining tank. There was absolutely no provision made to evacuate it off the floor of the tank. Zermatt possibly was counting on natural evaporation to do the trick.
7. And the most glaring defect of all : The entire floor of the STP retaining tank was made level, with no slope to the floor, and no a sump to collect drainage water. After every spell of rain, water would collect and stagnate on the floor of the STP, and the STP would double up as a swimming pool for the benefit of hard working software engineers on campus.
And there was a very fundamental and basic question I posed to both Zermatt and the project team of the client :
Where, Oh! Where was the need to build an entire retaining tank structure below ground to house the STP ? All that was needed was for the first Collection/ Equalisation tank to be below ground, and all other structures could be very simply erected at ground level.
And what of the Cost factor for this brilliant piece of engineering ? Left to me, I would have designed and engineered the entire STP at a cost less than that incurred for just constructing the fortress like structure housing the STP !!!
Dr. Ananth S Kodavasal August 14, 2011
No comments:
Post a Comment