Examination of a Full-Scale Model for Post-wildfire Water Quality Mitigation Solutions

The objective of this study is to determine a potential low-cost, sustainable, and rapidly deployable solution for post-wildfire water quality mitigation in communities reliant on surface water for drinking water. Coalinga, Fresno County, California was selected as a study area for a full-scale solution due to its high risk of wildfires, high social vulnerability, and relatively low community resilience. A bench-scale demonstration of the system directs water into a gravel infiltration zone surrounded by a weir perimeter and followed by a clarifier. Because of their regional abundance, almond shells were explored as a coagulant additive to the clarifier for turbidity and total suspended solids (TSS) removal. Almond shells with particle sizes of sieve No. 80 (0.18 mm) – No. 50 (0.3 mm), No. 50 – No. 30 (0.6 mm), and No. 30 – No. 20 (0.85 mm) were tested at dosages of 0.075 g/L, 0.1 g/L, and 0.25 g/L, agitation rates of 10 revolutions per minute (RPM), 25 RPM, and 50 RPM, and at high and low agitation positions.The complete system was able to achieve 96% turbidity and 99% TSS removal. The results of this study determined that almond shells of sieve size No. 50 – No. 30 at a dosage of 0.1 g/L and an agitation rate of 10 RPM with a low agitation position exhibited the most removal capabilities. When performing in a jar test, almond shells following this criterion were able to remove over an additional 7% of turbidity compared to the control sample. This study found the proposed solution to be feasible and appropriate for further development.