Denitrifying bioreactor clogging potential during wastewater treatment

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Bioremediation

Background:

• Woodchip bioreactors are a low-cost method for treating agricultural nitrogen pollution.
• There's increasing interest in using woodchip bioreactors for aquaculture wastewater, which has higher total suspended solids (TSS) and chemical oxygen demand (COD).

Purpose of the Study:

• To evaluate the impact of hydraulic retention time (HRT) on COD and TSS removal in woodchip bioreactors.
• To assess the potential for woodchip clogging in aquaculture wastewater.

Main Methods:

• Four pilot-scale woodchip denitrification bioreactors were operated for 267 days.
• Hydraulic retention time (HRT) was varied to assess its impact on performance.
• Woodchip clogging and phosphorus accumulation were monitored.

Main Results:

• Excellent TSS removal (>90%) was observed, primarily near the bioreactor inlet.
• COD removal was maximized at lower HRTs, with 56% efficiency at a 24-hour HRT.
• Wastewater flow through the woodchips slowed over time due to settling, clogging, and flow dynamics, particularly at higher loading rates.
• Phosphorus content in woodchips increased significantly, indicating solids removal but also potential for future nutrient release.

Conclusions:

• Woodchip bioreactors demonstrate excellent nitrate-nitrogen and TSS removal, with notable COD removal, making them viable for aquaculture wastewater.
• Potential clogging issues necessitate using woodchip bioreactors downstream of a filtration device for optimal and sustained performance.