Experimental Study on Slime Formation with Wastewater Recycle Systems : Part 1-Reactionship between Quality and Slime Formation

Abstract

Wastewater reuse, whose main purpose is to take appropriate measures for water saving such as recyclic use of water and practical utilization of wastewater in order to help preserve the water resources of the earth, and which can be used as a water recycling system, was specifically developed and put to practical use to respond to an increasing rise in demand for water principally in the center of the large cities in Japan. In this research we deal with slime problems which are responsible for a sharp reduction in the amount of flow through distributing pipes, the clogging of those pipes, the greatly reduced efficiency of heat exchangers or regenerators and an increase in local corrosion resulting from the depositing of slime on the internal surface of the pipes. In view of water quality, let us then consider the subject in detail. A series of experiments are carried out to find an effective way of preventing formation of the slime with a particular emphasis on a major factor in slime formation and on the form of the slime in relation to the quality of the recycled water. The results of the research can be summarized as follows: 1) Where raw effluent and artificial sewage are used in slime formation in pipes, each of the water samples treated by coagulation and sand filtration can be reduced to 30% and 10% of the slime volume respectively; 2) The presence of a chemical compound made of nitrogen (N) or phosphorus (P) as a nutrient in water has a profound influence on the formation of slime. In particular, the presence of P is a main factor in slime formation; 3) Formation of the slime has turned out to change over time in the form of first-order reaction; 4) The composition of this slime is expressed in Chemical Formula C_7H_<12>NO_6. The composition of the slime is similar to that of one of the bacteria as a living organism. Support for the above argument can also be found from the biological activity resulting from oxygen consumption by that organism.