EnviroMix delivers completely mixed anoxic zones with low-maintenance BioMix system

Water Reclamation Facility (WRF) in Ventura, California  

BioMix nozzles are distributed uniformly across the basin floor to improve efficiency and prevent solids from settling in the corners. 

The Ventura Water Reclamation Facility (WRF) is a tertiary treatment plant located about 70 miles northwest of Los Angeles near the mouth of the Santa Clara River. Currently, most of the plant’s treated wastewater is discharged into the estuary after flowing through a series of wildlife ponds for about four days. In 2017, HDR Engineering began working with the city to update the WRF aeration blower system, which was installed in 1971.  

Challenge

HDR was also tasked with reviewing alternative mixing technologies for the anoxic zones of the BNR basins. The existing technology — ten submersible mixers with a combined 60 HP — had been found to be ineffective. The plant consistently experienced issues with sludge settling in corners of the tanks and going septic. These issues created process upsets and labor-intensive maintenance demands to clean out the tanks.

Solution

Based on Ventura’s priorities of energy efficiency, low maintenance demands, and a completely mixed environment, EnviroMix’s BioMix Compressed Gas Mixing System was selected to mix the two anoxic zones.

When they first received an introduction to BioMix, the Ventura operators were skeptical — the low-maintenance system sounded too good to be true. However, as plant supervisor John Willis stated, “Once it was installed and online, we just went, ‘Wow, this stuff works!’” 

Correct nozzle density is critical in the design of a compressed gas mixing system. 

Prior to the upgrade, the staff would check the tanks every month or so, and they would find septic sludge in the corners. With BioMix in the anoxic zones, the operators saw that the tanks were completely mixed. “There was nothing in the corners. I have my guys dip the corners every so often with sludge judges, and there’s nothing there,” Willis said.  

Regarding maintenance and operations, the BioMix system has been much less labor intensive than the mechanical mixers were. In the past, Willis’s staff would have to adjust the mixers to certain levels and angles in the tank on a regular basis. As for the BioMix system, Willis commented, “So far, there’s literally been no maintenance.” 

The duty and standby compressors, which are easy to access, are the only components that require routine, scheduled maintenance.

The last doubt the operations team had was EnviroMix’s claim that BioMix provides complete mixing with negligible oxygen transfer. As part of the installation process, EnviroMix provided performance testing, measuring the negligible dissolved oxygen (DO) in the anoxic zones in direct comparison with the former mixing system. Willis said, “That was part of our skepticism — the oxygen transfer. But there is none.”

Results

EnviroMix’s BioMix Compressed Gas Mixing System provides the Ventura WRF completely mixed anoxic zones while delivering estimated energy and maintenance savings of more than $60,000 per year.