Deployable Decentralized Biofilm System to Degrade Organic Carbon, Nutrients and Benzene from Wastewater

Decentralized wastewater treatment systems are of great importance to protect the environment and people's health in the areas without centralized treatment system. Utilizing laboratory cultivated inoculating microorganisms (suborder Corynebacterineae including Agrobacterium sp. and Gordonia sp.) in logarithmic growth stage, a deployable aqueous aerobic bioreactor (DAAB) system was developed for decentralized wastewater treatment. The system is flexible, deployable in a standard shipping container, quick to start, and capable of removing organic carbon, phosphorus and benzene from wastewater. Experimental results indicated that the inoculated consortium had a faster COD removal rate than sewage-born microorganisms during the startup of the system. During the startup period, the removal of total phosphorus in the aeration tank followed a pseudo first-order kinetics (R² = 0.90) with a rate constant of 0.027 hr ^–1. The Agrobacterium sp. are likely responsible for the removal of phosphorus from wastewater. No ammonia removal was found in the aeration tank during the startup phase. After the system was in continuous operation with an average flow rate of 11.4 L/min, the removal efficiency of BOD₅ and total suspended solids (TSS) was 83±32% and 84±9%, respectively. The relative large standard deviation of the removal efficiencies is likely due to the small equalization capacity of a small treatment system to resist the variations of the incoming wastewater quality and shock loads. As an important supplement to the pilot studies, laboratorial tests by headspace analysis showed that the Gordonia sp. were able to degrade benzene from wastewater. After 26 hours, more significant biodegradation of benzene was found in sessile form (57±8%) than in planktonic form (25±11%) with minimal glucose. However, no benzene degradation was found in sessile form when no glucose was provided. The result suggested that the Gordonia sp. could not utilize benzene as the sole carbon and energy source.