Natural treatment of domestic wastewater and desert soil restoration using green soil amendments

This study evaluated the combination effect of soil amendments with sandy soil on wastewater contaminants removal, and the ultimate impact on soil restoration. A soil column experiment was conducted with sandy soil (CK) or soil amended with 4% (w/w) compost, biochar or maize straw. Wastewater infiltration was recorded, and alfalfa was planted subsequently. Results showed that amendment of biochar and straw significantly decreased domestic wastewater infiltration rate in sandy soil, with a reduction of 62 and 50% compared to CK. All combination of soil and amendments had removal ability for wastewater contaminants, as indicated by the sorption capacity and the resist for desorption. The largest sorption capacity was found in biochar-amended soil. Plant and soil microbes also played important role in contaminants removal. The amendment of biochar and compost significantly improved plant growth, microbial abundance and diversity. The plant biomass of compost and biochar treatments was 3.8 and 4.6 folds of CK. After plant harvest, straw and compost treated soil had increased soil aggregates compared to CK. It is concluded that sandy soil-organic amendments-plant system could be used as an efficient wastewater treatment strategy for nutrient and pathogen removal. Moreover, wastewater input and plant cultivation could improve structure of the coarse-sandy soil.