Short Term Variability of Humus Tank Performance Using Low‐Rate Trickling Filters for Wastewater Treatment

ABSTRACT This paper investigates the variability of low‐rate trickling filter humus tank performance. Data from 41 sites has highlighted large intersite differences in daily variability around the cyclical seasonal average. An approach using turbidity data from 6 years of operation and calculation of deviation from seasonal performance has confirmed a strong relationship linking variability to filter wetting rate. These relationships give new insight into performance, capability and compliance risk within a regulatory framework dominated by compliance based on upper percentile performance. They enable design and operation to meet present and future effluent TSS requirements with reduced risk of compliance failure for TSS and associated parameters. The relationships offer a quantitative approach for design and operation to assess the ability of existing trickling filters to continue to provide sustainable, low carbon wastewater treatment for the future with a greater degree of confidence.