Tapioca Starch Wastewater Treatment

Salem in Tamilnadu is the land of tapioca, starch and sago.  Over several visits to these factories about 15 years ago, a simple and cost effective Treatment scheme was developed for treating these highly polluting wastewaters from starch production operations.  However, recent reports suggest that many factories have not yet installed proper waste treatment facilities. Not that the farmers lack the funds for putting up these plants.  The principal reason is official apathy and laissez faire attitude that also helps bring in big bucks for turning a blind eye to environmental pollution, so common in our country.

50. STARCH, TAPIOCA SAGO  WASTEWATER TREATMENT

Around Fifteen years ago, I made a number of trips to the sleepy little town of Salem in central Tamilnadu.  I was invited by SAGOSERVE, a Cooperative undertaking of the Salem District Starch and Sago Producers to study their production process and recommend a suitable treatment scheme for the wastewaters generated in the process.  It was a pleasant enough drive of  5 hours to Salem from Bangalore via Hosur, Krishnagiri, Dharmapuri and the Thoppur Ghats, at a time before the toll Expressway was even contemplated.

http://www.sagoserve.com/

I am ashamed to confess, up until that time, I had imagined that Sabudana (Jawwarisi in Tamil) was a grain crop akin to rice or wheat, grown in vast green fields of the stuff, rippling and swaying  in the breeze.

Sabudana or Sago pearls are manufactured products from starch milled out of Tapioca tubers grown extensively in and around Salem.  Tapioca is called by different names in different parts of the world : native to the Amazonian jungles of South America, tapioca’s high food and nutritive value found it quickly proliferating all over the world, thanks to the colonizing powers such as Portugal, France etc.  Colonialism of previous centuries did indeed have many positives to its credit.  Called Yuca ( not Yucca) in its native lands,  Manioc in France and French speaking Africa,  Cassava in English speaking colonies, the root tubers are rich in starch, Calcium, Phosphorus and Vitamin C with little fat or proteins.

Just a few miles outside of Salem town, I visited one of the larger and more progressive tapioca farmers and starch manufacturer.  The rich bounty that this magic crop had brought to this humble farmer was plain to see.  In the midst of a vast plantation of tapioca now stood a modern Bungalow, displacing the thatched hut of not many years ago : A gleaming Mercedes Benz stood in the portico earlier occupied by the bullock cart : and a little distance away the Starch and Sago factory was humming with activity,  women and child labourers busily peeling the freshly harvested tubers and cutting them into pieces 3 to 4 inches long to be fed into the hungry jaws of the milling machine.  A modern day replica of the Tea Estates from a century ago : only the charm of the hills, the panache of the Planters and their style was missing in the hot plains of Salem.  I hasten to add this is in no way meant to be derogatory of these tapioca farmers.  True sons of the soil, they were gracious hosts in their own way, entirely without artifice and humbug: a first generation of farmers reaping the rich rewards now for the blood, toil, tears and sweat of their forefathers who tilled these same parched lands for a subsistence living.

The cut tapioca tubers are crushed and milled along with added water in a roller crushing machine ( like the ones used for crushing sugarcane, but only much larger ) to produce what the locals call the “milk” of tapioca. Milk white in colour, the milk or the slurry is allowed to settle in large shallow basins, when the solid starch particles settle out, and the supernatant water is drained off.  The solid starch is then heated lightly to retain the right amount of moisture, after which it is fed into a vibratory screen like contraption, where the solids form themselves into tiny round pearls, rolling, tumbling and dancing off the machine as Sabudana.

It is critical to process the tubers within a day of harvest : otherwise, enzymatic action under mildly acidic conditions converts and reduces the starch ( a polysaccharide) to its several hydrolysis products such as maltose, dextrose, fructose and glucose.  Starch is basically insoluble in cold water, but not so the lower saccharides.

The wastewater from the starch and sago making operations is mainly the supernatant drawn off form the settling basins.  Some of the salient features of this industry in Salem and the wastewater characteristics are  :

Number of Sago units                             : 700 to 800 ( in the year 1995 -96)

Processing Capacity of plant                   : 50 to 150 MT per day

Wastewater generated                            : 200 to 600 cum/d

Biochemical Oxygen Demand ( BOD)       : 4000 mg/L ( easily biodegradeable organic matter)

Chemical Oxygen Demand ( COD )         : 5500 mg/L

pH                                                                     : 5.0 to 5.5

At the time of my visit there was not a single treatment plant in the entire industry : however, pressure was building up for setting up treatment plants both from the Tamilnadu Pollution Control Board as well as the Green bench of the Madras High Court.

Some of the Design considerations and criteria I had set for myself in this environment were as follows:

-          Rural setting of the starch and sago units

-          Seasonal nature of operations ( Peak/ Lean)

-          The Farmers predisposition towards this unexpected expenditure

-          Historical argument of “ No harm done to the soil or groundwater”

-          No previous prototype or precedent of treatment plant

-          Low level of operator skills

-          Maximise local materials in construction of treatment plant

-          Minimise costs

-          By products utilization for beneficial use

The final design presented to SAGOSERVE for a 200 / 100 KLD ( Peak/ Lean season ) plant consisted of a an Anaerobic digestor in two compartments ( one compartment working during lean season), followed by an Aerobic treatment stage.  Excess sludge would be dried and disposed off from sludge drying beds, area availability not being of concern.  About 300 cum/d of biogas would be generated from the anaerobic digestor, containing approx. 65 % methane, which could be productively used as fuel in the drying operations of starch and sago in the factory.  Total cost of the plant was projected at Rs. 18-20 Lakhs, which was quite economical for a plant of this size.  Total land area required for the treatment plant would be around 800 Sqm.

Treated water with BOD level of 100 mg/L or less would be reused on the tapioca fields for irrigation

The design was well received both by SAGOSERVE and the farmers I had visited during my trips to Salem.  The Pollution Control Board too was quite happy to have a workable design to meet their stipulated quality of treated water : and I was happy to have contributed a little bit in cleaning up the environment around Salem town.

Dr. Ananth S Kodavasal                                                 December 29, 2011

P.S. : Every visit to Salem brings to mind an old friend of mine.  Rangarajan Kumaramangalam represented the Salem Parliamentary constituency in the years 1984-1996 as the Indian National Congress candidate and was a Minister in the Narasimha Rao Govt.  Later, he switched to the BJP and was elected from the Trichy Parliamentary constituency, and served also as a minister in the Vajpayee Govt.

Ranga was squat and heavy built in the six years I knew him as a classmate in the Madras Christian College School and was promptly nicknamed “The Rhino”.  Ranga hailed from an illustrious family of Tamilnadu who served with distinction both in the State and National politics.  A suave and accomplished politician, and an unassuming soul, Ranga died young at the age of 48.  R.I.P

http://en.wikipedia.org/wiki/Rangarajan_Kumaramangalam