Biologically Enhanced Primary Treatment: A Summary of Experience from Pilot, Demonstration, and Full-Scale Systems

摘要

Municipal wastewater is now being considered a valuable resource containing not only water for reuse, but also energy, nutrients, and organic chemicals. A novel biologically enhanced primary treatment (BEPT) process, first investigated in the 1990s, the Captivator® System has gained acceptance among carbon diversion technologies as evidenced by its selection as a featured Technology Spotlight process in the Water Environment and Reuse Foundation (WE&RF) Leaders Innovation Forum for Technology (LIFT©) program in January 2016, and full-scale implementation in 2014. The BEPT process blends waste activated sludge (WAS) with screened, de-gritted wastewater in a contact tank prior to separation in a dissolved air flotation (DAF) separator. It has been found that the WAS enhances suspended solids removal in the DAF, and results in removal of some soluble organics which increases the amount of total BOD diverted to anaerobic digestion while reducing aerobic oxidation in the downstream aeration tank. This diversion is capable of increasing biogas production at a wastewater reclamation facility (WRF) employing conventional primary treatment by as much as 40%, while simultaneously reducing the amount of carbon oxidized in the mainstream activated sludge process by a similar percentage. This BEPT process has been shown to be a unique and cost-effective alternative to other carbon diversion systems, being able to extract not just higher levels of particulate BOD but also extracting a substantial amount of soluble BOD while providing a thickened sludge for anaerobic digestion. The process has been validated through piloting and full-scale perfonnance, and has been reviewed by consultants and municipalities, showing 50+% BOD and 65+% TSS removals without chemical addition depending on wastewater characteristics. Pilot testing has also shown the ability to generate 4%+ thickened sludge without the need for polymers. The world's first full system came online at the Agua Nueva WRF, Pima County, Arizona in January 2014. Long term full scale performance and additional demonstration trials have confirmed the capabilities and benefits of the process.