Abstract
In this study, the effectiveness of mineral pumice application in sewage treatment in the dairy industries was investigated, with various factors such as adsorbent dose, mixing speed, pH and contact time being studied in detail. The results obtained showed that mineral pumice in a granular form, with a contact time of 20 hours and a volume fraction of one third and pH of 8 has the ability to COD (Chemical Oxygen Demand) decreasing up to 56.9%. However, by using mineral pumice in powder form, in three cases considered, higher efficiency than for pumice granules has been observed. It seems that acidity conditions do not have a positive effect on this efficiency. As the contact time increased, the adsorption rate increased, mostly due to increased probability of collision with the adsorbent surface. With an increasing adsorbent dose, the absorption rate also increased, especially in the range of 15 g/l. Regarding the mixing speed, no definite conclusion can be drawn, because in some cases, with increasing mixing speed, the COD reduction efficiency decreased. Considering the use of mineral pumice in reducing COD, in accordance with to the obtained results, it is better to use mineral pumice in granular, rather than in powder, form.