Use of volcanic ash and its impact on algae proliferation in drinking water filtration

With increasing pollution of the available water resources, development of safe drinking water supplies is increasingly becoming a challenge, both for developing and developed countries. To alleviate the prevailing difficulties, approaches should focus on sustainable water supply and treatment systems that require minimal maintenance and operator skills. In this study, a pretreatment of water containing algae using a combination of volcanic ash (VA) and sand in a filtration system was assessed. The results indicated that a combination of VA and sand performed better in the removal of algae than sand alone. However, it was noted that different algae genera were removed at different rates within the two types of media arrangement. In addition, there was an increase in the filtration run length of the ash-sand columns with VA on top of sand of about two and half times compared with the sand columns. It is therefore anticipated that pre-treatment of raw water laden with algae using ash-sand would probably improve on the performance of the subsequent conventional processes in removing intact cells of algae and thus reduce the threat of releasing toxins into the water that may not be removed by the subsequent conventional treatment processes.