Abstract
Slow sand filters (SSFs) have been widely used in the construction of water plants in rural areas. It is necessary to find river sand of suitable particle size to improve SSF treatment of micro-polluted water so as to ensure the effective and long-term operation of these plants. In this study, SSF1# (particle size of 0.1–0.5 mm), SSF2# (particle size of 0.5–1 mm), and SSF3# (particle size of 1–1.5 mm) were selected. The physical absorption, CODMn and NH4+-N removal effect, and microbial community were analyzed. According to Langmuir and Freundlich adsorption model fitting, the smaller the particle size of the river sand, the more pollutants are adsorbed under the same conditions. SSF1# has the shortest membrane-forming time, highest CODMn and NH4+-N removal rate, and highest Shannon estimator, indicating that there are more abundant microbial species in the biofilm. Mesorhizobium, Pannonibacter, Pseudoxanthomonas, Aquabacterium, Devosia, and other bacteria have different proportions in each system, each forming its own stable biological chain system. The effluent quality of the three SSFs can meet drinking water standards. However, river sand with a particle size range of 0.1–0.5 mm is easily blocked, and thus the recommended size range for SSF is 0.5–1 mm.
Highlights
Waterborne diseases remain a major cause of illness and death in areas without access to safe drinking water [1]
Oxygen content is very important for the growth and reproduction of bacteria, which affects the activity of nitrification bacteria, thereby affecting the purification effect of the whole reactor
It can be seen that the curves of the adsorption experiment of river sand with three particle sizes are basically the same
Summary
Waterborne diseases remain a major cause of illness and death in areas without access to safe drinking water [1]. Contaminated water can transmit diseases such as diarrhea, cholera, dysentery, typhoid, and polio. Contaminated drinking water is estimated to cause. 485,000 diarrheal deaths each year as a result of 144 million people collecting untreated surface water from lakes, ponds, rivers, and streams [2]. The main characteristics of micropolluted water are organic matter, ammonia pollution, obvious smell, some water quality indicators beyond the “Surface Water Environmental Quality Standard” (GB3838-2002). Ammonia is ubiquitous in water sources due to human activities. Ammonia nitrogen is the main cause of water eutrophication and an important source of nitrogen in water. Water eutrophication can seriously deteriorate the water environment and is harmful to source water [3,4]
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