Wastewater Treatment and Wood Production of Willow System in Cold Climate

This article studied how wastewater treatment performance of a short rotation forestry system was influenced by the seasonal operational changes under the extreme Mongolian winter conditions. For this reason, two beds planted with Willow (Salix spec.) and Poplar (Populus spec.) trees were operated over a period of two years under two different seasonal conditions: (A) external winter storage and (B) internal winter storage of pretreated wastewater. For operational condition A, the tree-bed was loaded with wastewater for only 4 summer months. For this operational condition it was considered that the treatment bed was fed with primary treated wastewater, which was stored in a sealed pond during the remaining 8 months. The other Bed B was irrigated throughout the year (12 months) with the same daily loading rate. In winter, the wastewater accumulated as ice in the tree-bed. Bed A, with external winter storage, showed mass removal percentage up to 95%, while the bed with internal winter storage showed mass removal rates up to 86% for pollutants such as COD, BOD5, TN, and TP. A high yield of biomass was recorded for both beds with slight differences. Based on the results, a design recommendation was developed for full-scale systems of short rotation coppice irrigated with wastewater under various operational conditions, which show these systems to be a viable method for treating wastewater and producing biomass for energy production in Mongolia.

Automated summary

This study investigated the impact of seasonal operational changes on wastewater treatment performance in a short rotation forestry system under extreme winter conditions in Mongolia. External winter storage was found to significantly improve treatment efficiency compared to internal storage, with both systems showing high biomass yield with slight differences. Based on the results, design recommendations for full-scale systems were developed, demonstrating the viability of using short rotation coppice for wastewater treatment and biomass production for energy in Mongolia.