Waste Water Treatment: The Nature Of Wastewater Treatment

INTRODUCTION

The main aim of wastewater treatment is to produce wastewater that can be safely disposed off, without causing harm or infection in humans and other animals. Wastewater generated by all processes - ranging from the personal use of water to industrial use - needs to be disposed in rivers and lakes. The pathogens present in wastewater can cause serious enteric infections and therefore need to be removed before they can proliferate via the sources of water such as lakes and rivers. The conventional methods of wastewater treatment are successful in a considerable reduction of organic and microbial load in wastewater. They also make use of certain microorganisms that aid the purification process. Further studies in the field have lead

Domestic wastewater is generated in households as well as non-industrial businesses. It consists of a combination of blackwater (human feces and urine) and graywater (wastewater from washing, bathing and cooking). Sewage is made up of organic matter, carbohydrates, fats and proteins in addition to 99.9% of water. It always contains pathogenic microorganisms since they are present in the feces of infected individuals, irrespective of the absence or presence of symptoms. Few examples of the microorganisms present in wastewater are Cryptosporadium, Giardia and rotaviruses.

Industrial wastes and rainwater runoffs also contribute to wastewater. Industrial wastes include wastes from petrochemical, food, dairy, pharmaceutical, metallurgical industries and so on.

NEED FOR TREATMENT OF

A mixed population of heterotrophic bacteria is kept in the dark at 20 degrees for five days in a sample of 300ml of wastewater diluted by phosphate buffer (pH 7.2). Inorganic elements for growth, acclimated microorganisms and oxygen may be added to facilitate the BOD test. For the determination of carbonaceous BOD a nitrification inhibitor may be added. The amount of oxygen consumed by the microbes is measured at time 0 and then after five days of incubation, using chemical procedures, an oxygen electrode or BOD apparatus.

BOD is calculated using the equation: BOD (mg/L) = (D1-D5)/ P where D1= initial dissolved oxygen (DO), D5 = DO at day 5 and P= decimal volumetric fraction of wastewater utilized.

The BOD5 test is most commonly used. In addition to the determination of the amount of oxygen required for the biological treatment of organic content in wastewater, this method gives insight into the required size of the treatment plant, efficiency and compliance with permits concerned with wastewater