The Effects Of Dissolved Organic Matter On Generation Of H₂O₂ And Degradation Of DBS In Natural Water Biofilm Systems Under Illumination

Natural water biofilm is a complex community widely existing in water environment,it will generate hydrogen peroxide and other reactive oxygen species?ROS?through photosynthesis and other life activities under light conditions,which have strong oxidative capacity and are important factors affecting the migration,transformation and ecological effects of organic pollutants in the water environment.Existing studies have shown that ROS in natural water bodies can be generated by abiotic actions such as dissolved organic matter?DOM?photochemical reaction,and DOM itself can react with ROS in water and change its structure and properties.Therefore,the presence of DOM may affect the generation and presence of ROS in the biofilm system under visible light and the degradation of organic pollutants in the system.Microorganisms extracellular polymeric substance?EPS?is a kind of natural macromolecule organic matter,which is not only an important representative DOM components of natural water body,but also the main components of biological membrane.In addition,ethylenediamine tetraacetic acid?EDTA?is often used as a representative of small molecule DOM to study the role and behavior of DOM.In this paper,the effects of DOM on the generation characteristics of H₂O₂ and DBS degradation in natural biofilm systems were studied.And the effects of light and dark alternation,initial pH value,DOM concentration,dissolved oxygen?DO?and other factors were investigated.EPS and EDTA were chosen as two typical of the polymers and small molecules DOM components,with H₂O₂ as the representative of ROS,and sodium dodecyl benzene sulfonate?DBS?as the representative of the organic matter.To further understand the ROS production and DBS degradation mechanism and influencing factors of biofilms in the natural water of DOM and biofilm coexistence system.The results showed that the polymer DOM represented by EPS could generate H₂O₂ under light conditions and had an obvious effect on the degradation of DBS,but it could also inhibit the degradation of DBS to some extent by quenching the ROS in the system,so it had a dual effect on the degradation of DBS.EPS did not generate H₂O₂ in the dark,but H₂O₂ existing in the system could still degrade DBS.At the same time,EPS had no significant effect on the biofilm production of H₂O₂,but EPS could inhibit the biofilm degradation of DBS to some extent.The amount of H₂O₂ and DBS degradation produced by EPS and biofilms in the medium and low pH system was higher than that in the high pH system.The increase of EPS concentration had no significant effect on the biofilm production of H₂O₂,but to some extent,it enhanced the inhibitory effect of EPS on biofilm degradation of DBS.The rise of DO inhibited the decomposition of H₂O₂ and significantly promoted the generation of H₂O₂ by EPS and biofilms,thus promoting the degradation of DBS.The small molecule DOM represented by EDTA could not generate H₂O₂ by itself,but it could significantly inhibit the generation of H₂O₂ of the biofilm,thereby inhibiting the degradation of DBS by the biofilm.EDTA had a more significant effect on inhibiting the biofilm production of H₂O₂ at high pH and concentration,and thus inhibiting the degradation of DBS.The increase of DO had no significant effect on the inhibition of biofilm production of H₂O₂ and degradation of DBS by EDTA.