Humus is a complex organic matter formed by animals and plants after long-term physical, chemical and biological actions, water sediment soil and so on contain humus, humus is a macromolecular polymer, the chemical structure is complex, all with carboxyl groups, phenol groups, ketone groups and other active groups, its molecular weight from 102 ~ 106. According to the difference in its solubility in acids and alkalis, humus can be divided into: humic acid, also known as humic acid (HA), fulvic acid (FA), and humus. The concentration of organic matter in natural drinking water, mainly HA, ranges from 20 μg/L in groundwater to 30 mg/L in surface water, and the higher the content, the worse the water quality and hygiene. The content of humic acid in general water sources is about 10 mg/L, accounting for 50%~90% of the total organic matter in the water, and the presence of humic acid in natural drinking water sources has brought a series of effects to humans, animals and plants:
(1) HA is a complexing agent for trace metal elements. On the one hand, the presence of humic acid will reduce the content of metal ions and trace elements in water, and reduce the degree of mineralization, thereby destroying the adsorption and balance of some elements such as Ca, Mg, Mn, V, Mo, SO2 -4, etc. On the other hand, it can affect the toxicity and bioavailability of metal ions.
(2) Humic acids in water are important precursors of halogenation by-products. Humus is very susceptible to the formation of disinfection by-products DBPs and trihalomethane carcinogens THMs during the chlorination process of water plants. It has been reported that almost all aquatic natural organic matter may be chlorinated during the disinfection process, and humic acid, which accounts for about half of the dissolved aquatic organic matter, is the most important precursor to the production of THMs. Studies have shown that dissolved humic acids are the main precursors for the formation of MX (a disinfection by-product with strong mutagenicity) in natural water, and some of these phenols, aldehydes and aromatic acids may play an important role in the formation of MX.
(3) Humic acid is one of the main environmental factors leading to KBD. The drinking water of residents in the KBD area is often dark and damp cellar water, which does not get sufficient sunlight, and the humic acid in the water has less photolysis, so the content is high.
(4) Acidification of water bodies causes changes in humus (HS) characteristics, which has an impact on the environment. With the continuous deterioration of the human living environment, the formation of acid rain, and the pH of natural water bodies such as lakes decreased. The organic nitrogen content of HS in the water body increased, the proportion of hydrophobic substances and hydrophilic substances decreased, the carbon content and carboxyl acidity decreased, the oxygen content and the acidity of phenols and aldehydes increased, which in turn led to the increase of fish toxicity and the primary production of phytoplankton and the disappearance of some major zooplankton species, the decrease of giant plants, and the increase of epiphytes in the treatment basin.
