The reject water produced in anaerobic digestion contains high concentration of COD, NH4-N, SS, oils, etc., which need to be strictly treated to meet the discharge standard. The SDN-N process is a technology developed by PURAC after years of exploration and practice, which adopts the nitrification-denitrification and the shortcut nitrogen removal simultaneous treatment process, combined with MTS jet aeration, and has achieved good results in the treatment of reject water from digestion. The effluent treated by SDN-N process and advanced clarification or ultrafiltration membrane filtration, can meet the wastewater quality standards for discharge to municipal sewers, with simple treatment process, low operation cost, and less maintenance requirement, which is especially suitable for the treatment of high organic waste and high ammonia-nitrogen wastewater, such as reject water from digestion.

SDN-N Features and Benefits:
- COD removal and nitrogen removal can be realized simultaneously, and the system is simple.
- The operation mode can be adjusted to deal with the shock load of influent water quantity and water quality.
- The jet pump is used to generate a large proportion of nitrification liquid internal circulation, and the aeration and mixing are realized simultaneously, which is simple to operate and low in operating cost.
- The water depth of the biological tank can be up to 12 meters, which can reduce the footprint.