Experimental Study on Slime Formation with Wastewater Recycle Systems : Part 2-Relationship between Piping Materials and Slime Formation

Abstract

In the part 1, as the foundamental matter of study, we studied the appearance, growth condition, inhibition and biological activity of slime. In this study, we fixed our eyes upon piping which supplied recycling water. In the case when microbes attach in the piping, it is said that the following hazard may be caused; choking of plumbing fixture, obstacles of flow, blockade of pipeline, generation of odors and acceleration of corrosion, etc. Under the circumstance, we specially investigated the followings. That is, (1) deposit of the slime in such piping materials as carbon steel pipes for ordinary piping, unplasticized polyvinyl chloride pipes, stainless steel pipes and acrylic pipes, (2) deposit of the slime caused by both flow velocity and fineness or coarseness of surfaces of pipes, (3) mutual relation of both water quality and formation of the slime, and nature of the slime. The results of the research can be summarized as follows: 1) Compared with raw water (BOD concentration is about 10mg/l), in the case of advenced treatment, deposit of the slime becomes extremely little. 2) In inhibiting effects of the slime in both coagulating sedimentation water and sand filtrate water, differences are shown because of both material of piping and sorts of the flow velocity. The formation of the slime becomes bigger according to the following order. That is, the acrylic pipes<stainless steel pipes<the unplasticized polyvinyl chloride pipes<the carbon steel pipes for ordinary piping. 3) It was recognized that the fineness or coarseness of the surfaces of pipes gives influences except the sand filtrate water. 4) The composition of the slime was shown with molecular formula of C_9H_<15>NO_4.