The Evolution Of Black-odor In River Water And The Formation Mechanism Of Odorous Sulfide

With the accelerating urbanization and industrialization,over discharge of domestic wastewater results in eutrophication,and even lead to smelly black water to form the black and odorous water.The black-odor water is a typical phenomenon of heavily polluted river.It is important to investigate the mechanism of water quality evolution for water pollution prevention and remediation.At present,the research about black-odor water mainly concentrates on the formation mechanism and the evaluation method of black and odorous water body.However,the study on the formation conditions of black-odor water and the formation of volatile sulfide in the odorous substances in water are obviously insufficient.In the present dissertation,combined the water quality characteristics of estuaries and coastal zones with the simulation experiment in the laboratory,influences of four important water quality factors such as total organic carbon?TOC?,total nitrogen?TN?,Fe²⁺ and salinity,on the formation of black-odor in water body are systematically studied.At the same time,the generation mechanisms of volatile odorous sulfides including methyl mercaptan?MT?and H₂ S were analyzed under different water quality conditions.Through setting the different concentration gradients of TOC,TN,Fe²⁺ and salinity during artificial preparation of black-odor water,inoculated mixed bacteria from river water the effects of varied factors on the formation of black odor water are sutdied repectively.Another objective of this study is to designed a multi-factor orthogonal test for further understanding the comprehensive influence of various water quality factors on the formation of black-odor water.The main conclusions are as follows:?1?Microbial action played a key role in the process of black-odor water.The result show that the microbial biomass have a obviously impact on the formation of black-odor water.With the increase of anaerobic microorganisms in the water body,the formation time of the black-odor water is reduced and the black and odorous phenomenon is more obvious,indicating that under the anaerobic condition,the black and odorous phenomenon is easily formed in water.?2?Carbon source is a important condition for the formation of black and odorous water.When the concentration of TOC is less than 50 mg / L,the water will not turn black,just produce a small amount of odor,and the total amount of H₂ S and MT will reach 21.83 ?g / L.When the concentration of TOC is more than 100 mg / L,the total amount of the MT and H₂ S are more than 1 g/L.At the end of the experiment,the chromaticity is over 500 degrees.?3?Nitrogen source is also a important condition for the formation of black smelly.When the concentration of TN is 0,the water body is not black and smelly.When ratio of C/N is less than 2:1,the formation of black and odorous water is slow.when C/N is ranged from 3:1 to 4:1,with the increase of the TN concentration during a certain range of TN concentration,the the formation time of black and odorous water decrease and the black-odor degree of warer is more obvious.?4?Fe²⁺ concentration is not only related to chroma,but also an important condition for the generation of odor.Our result show that,when Fe²⁺ concentration is over 10 mg/L result in blackened and turbid phenomenon in water,when Fe²⁺ concentration is less than 5 mg/L just lead to turbid phenomenon in water,indicating that the blackened degree is significantly raised with the increase of Fe²⁺ concentration.Besides,as the increase of Fe²⁺ concentration,the concentrations of MT and H₂ S are dramatically raised in water,which is attributed to promote the metabolism process of sulfate reducing bacteria,and then increase the concentrations of odorous sulfide.Thus,Fe²⁺ concentration has a obviously impact on the formation of black-odor water.?5?High salinity can inhibit the formation of black water.High salinity can inhibit the growth and metabolism of microbial processes.When salinity is more than 15 ‰,the inhibition was significant.In the less than 10 ‰ salinity range,salinity plays an important role in promoting the formation of black and odorous water.At the end of the experiment,the black and odorous degree in the water at salinity of 10 ‰ is the most significant,and the concentrations of MT and H₂ S exceeds 850 ?g/L.?6?The results of orthogonal test show that TOC has a significant effect on the black and odorous water and the effects of TN and Fe²⁺ on black and odorous water is obvious.Fe²⁺ concentration plays an important role in promoting the formation of odorous water.