Unit operations in salt water sewage treatment
Manchen, Kenneth L.
Kessick, Michael A.
Master of Science
A study was conducted to determine the effects of ocean salts on the nature and treatability of domestic sewage. The primary goal was to evaluate the effectiveness of physical chemical treatment, specifically chemical coagulation. One of the major analytical tests utilized in this work concerned the measurement of the chemical oxygen demand. The standard procedure was modified successfully for use in high salinity water. A minor modification was also employed in the determination of suspended solids. Formation of volatile suspended material was shown to occur upon introduction of sea salts to domestic sewage. The major compound precipitated was believed to be magnesium carbonate. Aluminum sulfate and lime were used in the coagulation studies. The results with aluminum sulfate demonstrated that coagulation with this chemical was more efficient when the ocean salts were present. Coagulation with lime was found to show the opposite effect. An additional and important result concerned the use of the biochemical oxygen demand test. Much lower oxygen demand values were found for unfiltered sewage after ocean salts had been added. Filtered sewage was found to exhibit the same oxygen demand whether or not the ocean salts were present. The lower values therefore appeared to be due to inhibition of breakdown of organic particulate matter.