Hampton Roads Sanitation District’s (HRSD) James River Treatment Plant of Newport News, Virginia and York River Treatment Plant of Seaford, Virginia each upgraded their wastewater treatment processes to better meet effluent requirements and reduce energy and external carbon consumption.
Multiple Upgrades at James River
The James River plant upgraded its existing integrated fixed-film activated sludge (IFAS) system with the AvN® control strategy to improve nitrogen removal efficiency at the lowest possible energy input. AvN enabled the James River plant operators to turn the post-IFAS zone into a partial denitrification anammox (PdNA) zone by using World Water Works’ specially designed moving bed biofilm reactor (MBBR) media, vertical mixers and a media retention screen.
By implementing AvN and dosing the PdNA zone with a carbon source, the plant operators increased the IFAS treatment zone capacity, enabling the ammonia load to shift to the PdNA zone. The capacity increase also reduces aeration energy consumption by nitrifying less and operating at lower dissolved oxygen (DO) levels — minimizing overall carbon usage for the plant while meeting very low effluent total inorganic nitrogen (TIN) values.
Anammox activity was detected on the MBBR media three months after the new IFAS-AvN-PdNA configuration. Currently, the total nitrogen (TN) removal rate in the PdNA zone is about 1.5 g/m2 per day.
Why AvN and Partial Denitrification Anammox?
PdNA provides a redirection of the conventional denitrification cycle necessary to remove nitrate-nitrogen from wastewater. This redirection is accomplished by first using the AvN control system. AvN enables wastewater treatment plants to spend less energy and resources on upstream nitrification processes by shifting ammonia loading to downstream processes.
The PdNA zone then uses a portion of the carbon requirement to convert the nitrate into nitrite. At the same time, the anammox bacteria living on the MBBR bio-media produce dinitrogen gas from the newly formed nitrite and remaining ammonia in the wastewater.
These methods reduce both energy and chemical consumption, and ultimately provide more efficient wastewater treatment.
Cooperative Efforts at York River
The York River Treatment Plant had fully aerobic conventional aeration tanks with downstream denitrification filters that required the addition of external carbon to meet its effluent TN limits. Since the aeration tanks lacked anoxic zones, the plant blowers were constantly running and consuming electricity to fully nitrify. The tanks also required large caustic and methanol doses.
To reduce the plant’s total energy and chemical consumption while improving nutrient removal efficiency and increasing capacity, the facility was upgraded with the AvN control strategy and specific anoxic and aerobic zones were created. This allowed for the implementation of PdNA treatment and a transition away from an entirely aerobic treatment process.
The new control strategy lowered plant energy usage because operators no longer needed to fully nitrify the wastewater. Additionally, AvN allowed anammox bacteria to grow in the existing downstream denitrification sand filters. By only feeding partial carbon to the denitrification filters, nitrate would convert to nitrite. Then, the anammox bacteria growing in the filter media would remove the newly formed nitrite and remaining ammonia. This strategy reduced carbon usage while lowering effluent TIN values. It also eliminated the need for caustic doses.
Cooperative efforts between HRSD, DC Water, local universities and World Water Works made the James River Treatment Plant project possible. Going forward, the studies done at the James River and York River Treatment Plants will help provide the groundwork to implement PdNA in other facilities.
Watch the video to learn more about this project.