Intermediate Nitrification/Denitrification Bioreactor

Background

Typically, wastewater treatment systems employ a septic tank to collect and partially decompose solids in the wastewater effluent from the septic tank. One known design is the Septic Tank Soil Adsorption System (SAS) in which septic tank effluent (STE) is sent to a soil treatment unit to provide secondary treatment for the STE. However, such systems offer poor nitrogen removal. Another known design is the Nitrogen Removing Biofilter (NRB), in which the STE is pumped from the septic tank to a treatment system comprising a nitrification sand layer. Oxygen is provided to the sand layer by natural aeration and nitrification occurs. Nitrification is the conversion of ammonia nitrogen to nitrate nitrogen. While this design can achieve desired low effluent nitrogen concentration, it requires a large ground footprint and has a high cost of implementation. Additionally, the performance of both NRB and SAS designs are subject to wide variations in daily STE flow, which can result in inefficient bacterial conversion of ammonia nitrogen to nitrogen gas. Thus, there is a need for a nitrification and denitrification method and process/system that achieves high levels of nitrogen removal, can meet low effluent nitrogen concentration requirements, provides for low levels of organic material, has a small footprint, and is economically efficient to implement and maintain.

Technology

Researchers at Stony Brook University (SBU) present a method for nitrification and denitrification of septic effluent comprising an intermediate nitrification/denitrification bioreactor which builds on concepts currently used in the design of full‑scale wastewater treatment plants. However, this design takes an approach in which wood chips are used directly after a sand filter. During the process, a portion of the sand filter effluent is recycled into an intermediate wood chip "box" for partial conversion of nitrates to nitrogen gas. The blend of septic tank effluent and nitrate reduced recycle is put back into the sand filter. The use of wood chips offers successful denitrification while reducing the size of component systems and thus reducing the cost.

Advantages

• More affordable
• Reduced system component sizes

Application

Wastewater treatment