What are the effects of suspended solids in water on water quality
Suspended substances in water are particles with a particle diameter of 1-10mm or more, visible to the naked eye. These particles are mainly composed of silt, clay, algae, bacteria, viruses, and high-molecular organic matter. They are often suspended in the water flow, and the turbidity of the water is also caused by such substances. Suspended matter in water plays a dual ecological role: 1. Beneficial role: organic debris (rot) formed by dead bodies of aquatic organisms or their metabolites is one of the important food sources for aquatic animals, and the amount of suspended debris often determines the planktonic The production of animals, and the rot debris deposited on the bottom of the water are the main food for benthic animals such as chironomus larvae and water earthworms. After the decomposition of bacteria, the humus can enrich the concentration of nitrogen, phosphorus and other biogenic substances in the water, thereby promoting the reproduction of phytoplankton. Therefore, under good other conditions, organic suspended matter can promote the improvement of water body productivity. 2. Unfavorable effects: The existence of inorganic suspended matter or excessive organic suspended matter will play an adverse ecological role. (1) Too much suspended matter in the water will drastically reduce the transparency of the water, inhibit the photosynthesis of aquatic plants, and worsen the condition of dissolved oxygen. (2) Suspended matter directly rubs against plankton, causing a certain degree of mechanical damage to the latter; in flowing water, inorganic suspended matter such as sediment also impacts and scrapes away attached organisms. (3) Too much suspended solids in the water can easily block the filter-feeding organs of filter-feeding animals and deteriorate their nutritional conditions. Thus, turbidity often reduces zooplankton populations. (4) Suspended particles in water also have an impact on fish, and inorganic particles with a diameter of several microns to 2-3 cm directly impact fish. The smaller eyes of shovel-nosed sturgeon and eelfish living in turbid water is an adaptation to reduce the possibility of being damaged by suspended matter in the water. Large amounts of suspended matter can also impede the respiration of fish and aquatic invertebrates. For fish living in turbid water, the mucus secreted from the skin can quickly sink the suspended particles. This adaptation makes the fish seem to maintain a clear water cover in turbid water. However, if the suspended solids in the water exceed a certain limit, fish can still die in large numbers due to clogged gills. (5) Coarse suspended particles, especially silt, are easy to settle. When a large amount of suspended matter settles to the bottom of the water, it can bury benthic animals and cause a large number of deaths. (6) Change biological composition. The main stream of the Yellow River in my country is not short of nutrients such as nitrogen and phosphorus, and the main water quality indicators such as dissolved oxygen and pH are within the normal range, but the amount of bait organisms is small, and the number of fish populations is also extremely limited. The reason is that it contains The amount of sand is too high.