Experimental evaluation of sequencing batch reactor with continuous feeding: a novel continuous batch process for wastewater treatment

BACKGROUND: This study experimentally tested and evaluated the organic carbon (COD) removal performance of a sequencing batch reactor (SBR) with continuous sewage feeding, to define a novel process scheme, the continuous batch reactor (CBR). The experiments involved two pilot plants: a CBR unit, and a conventional SBR unit with the same reactor volume, which operated with two cycles per day and intermittent feeding, for parallel evaluation. The study emphasized the effect of continuous feeding on COD removal and challenged the empirical practice of intermittent feeding. RESULTS: The effluent COD of the CBR unit remained within the bracket of 50–70 mg L⁻¹, with an average value of 67 mg L⁻¹, while the influent COD exhibited a significant fluctuation between 400 and 600 mg L⁻¹. The performance of the parallel SBR unit was quite similar. The cyclic soluble COD profile of the CBR unit was lowered down to a plateau right after entering the reactor, and remained constant throughout the process phase, as it primarily consisted of soluble inert COD fractions. The incremental sewage feeding during the idle phase exerted a minor increase in the effluent soluble COD level. CONCLUSION: The novel CBR scheme eliminated the need for multiple parallel reactors associated with conventional SBR systems operated with intermittent and short feeding periods. Continuous feeding, inherently avoided in conventional SBR operation, did not appreciably affect system performance. It also provided ideal operating conditions for aeration and complete substrate removal, since the incremental sewage feeding into the entire biomass would maintain a very low substrate-to-biomass ratio, leading to immediate substrate adsorption and utilization.