Application of denitrifying wood chip bioreactors for management of residential non-point sources of nitrogen

• Published in: Journal of biological engineering Vol. 11; no. 1; p. 16
• Main Authors: Lopez-Ponnada, E V, Lynn, T J, Peterson, M, Ergas, S J, Mihelcic, J R
• Format: Journal Article
• Language: English
• Published: England BioMed Central 01.05.2017; BMC
• Subjects: Air pollution; Ambient temperature; Bacteria; Best management practice (BMP); Bioavailability; Biofilm; Biofilms; Biofilters; Biofiltration; Biological activity; Bioreactors; Cellulose; Denitrification; Dissolved organic carbon; Environmental conditions; Eutrophication; Flow velocity; Green infrastructure; Hydraulic loading; Hydrolysis; Internal water; Lignocellulose; Load distribution; Loading rate; Low impact development (LID); Mathematical models; Microorganisms; Neighborhoods; New technology; Nitrate removal; Nitrates; Nitrogen; Nitrogen removal; Nitrogen sources; Nutrient removal; On-site wastewater treatment; Onsite; Packed beds; Permeable reactive barriers; Pollutants; Pollution prevention; Rain; Residential areas; Retention basins; Review; Runoff; Storm runoff; Stormwater; Stormwater management; Stormwater quality; Substrates; Systems design; Temperature effects; Wastewater; Wastewater treatment; Water quality; Water shortages; Water storage; Water use; Watersheds; United States > US; Low impact development (LID); Best management practice (BMP); Microbiology; Septic systems; Biofilm; Green infrastructure; Stormwater; Decentralized treatment; On-site wastewater treatment; Eutrophication
• ISSN: 1754-1611; 1754-1611
• DOI: 10.1186/s13036-017-0057-4

Two important and large non-point sources of nitrogen in residential areas that adversely affect water quality are stormwater runoff and effluent from on-site treatment systems. These sources are challenging to control due to their variable flow rates and nitrogen concentrations. Denitrifying bioreactors that employ a lignocellulosic wood chip medium contained within a saturated (anoxic) zone are relatively new technology that can be implemented at the local level to manage residential non-point nitrogen sources. In these systems, wood chips serve as a microbial biofilm support and provide a constant source of organic substrate required for denitrification. Denitrifying wood chip bioreactors for stormwater management include biofilters and bioretention systems modified to include an internal water storage zone; for on-site wastewater, they include upflow packed bed reactors, permeable reactive barriers, and submerged wetlands. Laboratory studies have shown that these bioreactors can achieve nitrate removal efficiencies as high as 80-100% but could provide more fundamental insight into system design and performance. For example, the type and size of the wood chips, hydraulic loading rate, and dormant period between water applications affects the hydrolysis rate of the lignocellulosic substrate, which in turn affects the amount and bioavailability of dissolved organic carbon for denitrification. Additional field studies can provide a better understanding of the effect of varying environmental conditions such as ambient temperature, precipitation rates, household water use rates, and idle periods on nitrogen removal performance. Long-term studies are also essential for understanding operations and maintenance requirements and validating mathematical models that integrate the complex physical, chemical, and biological processes occurring in these systems. Better modeling tools could assist in optimizing denitrifying wood chip bioreactors to meet nutrient reduction goals in urban and suburban watersheds.