Effects Of Slow Release Carbon Source On The Denirification Efficiency Of Humus Media Filter

Humus media filter is a novel sewage treatment technology,which is a kind of bio-filter with humus media（or aged refused）as the main filler;When using biological technologies to reat low carbon nitrogen ratio wastewater,external carbon source is usually required to add into the denitrification unit,in order to achieve a substantial treatment efficiency of total nitrogen（TN）and then meet the national discharging requirements.Traditional external carbon sources are mostly liquid organics,which have the disadvantages of secondary pollution,multiple additions,and high cost.In this study,the carbon-releasing ability,secondary pollutant release,and solubility in natural state of five materials including rice,corn,mushroom residue,rice husk,and wheat straw and their respective thermal and alkali-modified materials were studied.According to other indicators such as the release ability of organic matter and the color of the effluent,the most suitable one in each group was selected.Then,taking the blank as a reference,a comparative study of slow-release carbon source-humus media filter on wastewater with low C/N ratio was carried out,and the most suitable one was screened out.Finally,a four-stage serial slow-release carbon source humus media filter treatment process was constructed,and the effect of slow-release carbon sources on the denitrification efficiency of the humus media filter was studied.The main conclusions of this sudy are as follows:（1）In the natural state and the state after heat treatment of the five materials,the release of COD is a rapid and large release in the initial stage,and then decreases,while the process of COD release from the alkali-treated materials is relatively stable;the carbon source release process of each material conforms to the second-level release process Kinetic equation and Ritger-Pepass equation;the DOM fluorescent components of the leaching solution of the five natural materials are mainly tryptophan-like and tyrosine-like proteins,and contain a small amount of humic acid and fulvic acid;the five materials and The release law of N,P and other secondary pollutants released by their heat-treated materials is similar to the carbon release law,both of which are released rapidly and in large quantities at the initial stage,and then the rate drops to a lower level;the alkali-treated materials release N,P and other secondary pollutants The release law of the carbon dioxide is also similar to their respective carbon release law,and the release process has been relatively smooth;comprehensively compare the experimental conditions of carbon release capacity,biodegradability of leachate,secondary pollutant release,DOM organic matter release and chromaticity.Select the most suitable slow-release carbon source in each group for device experiment,they are:rice（heat）,corn（alkali）,mushroom residue（alkali）,rice husk（alkali）,wheat straw（alkali）;（2）Under the condition of 3 L water inflow,C/N ratio of influent 3,water inflow time of 8 h,hydraulic load of 0.5 m³/（m²·d）,volume ratio of carbon source to filler 1:6,no ventilation and no return flow,Using rice（heat）,corn（alkali）,mushroom residue（alkali）,rice husk（alkali）,and wheat straw（alkali）as carbon sources,a blank control was set,and the slow-release carbon source-humus media filter was used to compare the low temperature.C/N ratio simulation wastewater treatment research,the results show that the corn（alkali）and rice husk（alkali）reactors have the highest average removal rates of COD,reaching 79.40%and 78.64%,respectively;except for rice（heat）and mushroom residue（In addition to alkali）,depending on the adsorption capacity of microorganisms and materials on the humic waste,the removal rate of NH₄⁺-N by each reactor reached more than 70%;the removal rate of TN by mushroom residue（alkali）and corn（alkali）reactors However,most of the reactors have the phenomenon of insufficient carbon source;the blank control has the highest removal rate of TP,followed by corn（alkali）,indicating that the removal of phosphorus by the slow-release carbon source biological filter mainly depends on the precipitation of the matrix itself.and adsorption properties of the material.Taking into account the treatment efficiency of each pollutant index and the color of the effluent,corn（alkali）was selected as the most suitable slow-release carbon source;（3）A four-stage series humus media filter with corn（alkali）as slow-release carbon source was used to treat simulated wastewater with low C/N ratio.Under the operating conditions of 12 h influent time and1L/min ventilation per hour（lasting for 5 min）,the effects of influent C/N ratio,hydraulic load,effluent reflux ratio and carbon source to filler volume ratio on the efficiency of low C/N ratio wastewater treatment were studied by using the control variable method.The operation parameters were optimized.The results showed that the four factors had a greater impact on the removal effect of COD and TN than NH₄⁺-N and TP.At present,the optimal operation mode is:continuous water inflow,intermittent central pipe ventilation,surface hydraulic load of 0.5 m³/（m²·d）,water inflow of 5 L,influent C/N is 3,hourly ventilation of 1 L/min,lasting for 5 min,effluent reflux ratio of 30%,carbon source and filler volume ratio of 1:3.At this time,the removal rates of COD,NH₄⁺-N,TP and TN are about 89.95%,96.58%,85.17%and 90.17%.In summary,this paper studies the carbon-releasing ability of various materials,and uses a slow-release carbon source humus media filter to treat low-carbon nitrogen ratio wastewater.The treatment efficiency and main influencing factors of carbon-nitrogen ratio wastewater were optimized,and the process parameters were optimized to achieve a high removal effect on low-carbon nitrogen ratio wastewater,which provided a certain theoretical support for exploring new denitrification treatment processes.