Contaminant removal and optimal operation of bio-slow sand filtration water treatment based on nature-based solutions

The nature-based solutions (NBS) concept is closely related to sustainability, harmonious and green development, resource rational exploitation, coupled human health and environment, and ecological protection priority. Bio-slow sand filtration (BSSF) technology is a green water treatment technology with low energy consumption, simple operation, and a high removal rate of contaminants. To achieve low cost, easy management and secondary pollution avoidance in the process of removing contaminants in drinking water, the rational selection of biofiltration materials and the optimal combination of particle size are particularly important based on NBS. To effectively remove turbidity, organic pollutants, bacteria, and ammonia nitrogen by BSSF, three scenarios were summarized by considering the influence of sensitive parameter optimization and the external environment (temperature and velocity). We designed three BSSF water treatment testing devices, which were filled with bio-filter materials with different particle sizes (0.15-0.3 mm, 0.3-0.9 mm, 0.9-1.35 mm, and 0.3-0.9 mm), to carry out an indoor testing comparison analysis. We optimized important parameters of BSSF water treatment technology (such as the bio-filter material particle size and filling heights, filtering velocity, and suitable temperature) to obtain the best design and operational parameters of BSSF water treatment technology. The optimum operating conditions were: filter material particle size of 0.3-0.6 mm, filling height of 0.6-0.9 m, filtering velocity of 0.2-0.6 m/h, and a suitable temperature of 15-35ºC. To ensure the water quality of the filtered water, we optimized the design parameters of traditional BSSF technology, which could save land and reduce beginning time. BSSF water treatment technology based on NBS is useful for promoting the engineering application of drinking water treatment and regional water security.