GUWAHATI, March 24 ? The historic Dighalipukhuri, which added to the beauty of this picturesque city till the other day, is now stinking. Irrational behaviour of the people of this city, which is known since the days of the epics, is said to be the reason behind this degradation of the massive tank. Dighalipukhuri is connected with several myths. One such myth attributes its digging to the Mahabharata fame king Bhagadatta, the father-in-law of king Duryodhana. History of the State has its mention as a part of the city?s fortification in the pre-British period. The tank is one of the major attractions for the city?s strollers for its pleasant environment.
Today, the tank is emitting stench in the sun-lit days making life miserable for those who reside on its southern and south-eastern sides. Even for the passersby using the roads along the southern and south-eastern banks of the tank, the stench coming from the tank is obnoxious. The tank has its water covered with a thick carpet of green algae, which according to Pollution Control Board, Assam (PCBA) sources, may be the result of the availability of the required amount of nutrient to the growth of algae. This is in no way a healthy condition. For, high amount of algal death in the tank has been contributing dead bio-mass to the tank water everyday. This situation is aggravated by the throwing of municipal solid waste (MSW) from the nearby habitation on the bank of the tank. A considerable portion of this MSW, finds its way to the tank. And in the rainy season, may be the entire amount of the MSW land in the tank. This raises the load of organic pollutants in the tank.
Hence, the Biochemical Oxygen Demand (BOD) level in the tank water ranges between 9.4 miligram per litre (mg/l) and 16.2 mg/l, which is very high. The Chemical Oxygen Demand (COD) value of the tank water is also high ? between 64.5 mg/l and 95.2 mg/l. Such concentration of BOD and COD values is quite high for a clean surface water tank and this indicates considerable organic pollution, said PCBA sources. The safe BOD level for natural surface water is between 0 and 3 mg/l, the sources added. The tank has another source contributing to its misery, ? that is, the outlet at its south eastern end. Occasional backflow of highly polluted stagnant water from outside through this outlet during the rainy season also contributes to the high BOD and COD level and also to the stench the tank is now emitting, the sources said. The stench has one more contributing factor, ? the putrification of a portion of the MSW on the bank of the tank, said the sources.
The PCBA analysts who examined the tank water and surveyed the tank, mentioned one more reason as a contributing factor to this deplorable condition of the tank. In their report, they said that some people use the banks of the tank, particularly its eastern bank, as an excretory ground. Those people are, however, a part of the city?s floating population, they said. The Board analysts also said that the waste generated in the eastern side of the tank comes mostly from the Professor?s Colony, girls? hostels and the nearby localities.
PCBA sources said that water-borne pathogenic bacteria have been found in abundance in the tank and hence, the water quality of the tank is bacteriologically unsafe for drinking and bathing. The Board analysts suggested that to remove the stench the outlet of the tank should be cleaned and there should be a proper arrangement for the disposal of the MSW in the area along the eastern bank of the tank. They also suggested construction of a sluice gate at the end of the outlet to prevent the backflow. The existing municipal dustbins are needed to be replaced and the height of fencing on the eastern side of the tank should also be raised, they said.