Effects Of Ca²⁺ And Mg²⁺ On Anaerobic Biological Treatment Of Landfill Leachate

The high concentration of calcium and magnesium ions(Ca²⁺,Mg²⁺)in the landfill leachate of incineration plants has always been a problem in the anaerobic biological treatment of leachate,Since Ca²⁺and Mg²⁺may affect the activity and function of microorganisms,which affecting the effect of biological treatment,so research on the effects of Ca²⁺and Mg²⁺on anaerobic biological treatment is very important.However,there are few studies on the influence of Ca²⁺and Mg²⁺on the anaerobic biological treatment of landfill leachate at present,Therefore,the experiment used anaerobic sequential batch reactor?ASBR?to cultivation and domesticate the sludge from the nitrification tank of a waste incineration plant in Hefei.Study the effects of Ca²⁺and Mg²⁺on the effluent quality indicators of each reactor when the concentrations of 0,5,10,15,25,35,50,75,and 100 mmol/L are analyzed,the effects of Ca²⁺and Mg²⁺on the composition and functional groups of microbial extracellular polymers?EPS?were also investigated.The conclusion of the test is as follows:?1?The results of the ASBR start-up study showed that the entire start-up process lasted 74 days and the COD concentration in the influent increased from 2250 mg/L to22420 mg/L;As the volume load increases,the COD removal rate of the effluent shows an upward trend,by the end of the start-up phase,the volume load has increased from the initial 0.57 kgCOD/?m³·d?to 5.68 kgCOD/?m³·d?,the COD removal rate of the effluent from the reactor increased from 57.33%at the initial start-up to 90.87%;Throughout the start-up process,the VFA concentration in the effluent of the reactor was kept below 800mg/L,the pH of the effluent was in the range of 7.0-7.8 and showed an overall upward trend,and the ORP value remained basically between-400 mV and-440 mV.The test results show that the ASBR reactor was successfully started.?2?The results of studies on the effects of different Ca²⁺and Mg²⁺concentrations?0,5,10,15,25,35,50,75,100 mmol/L?on the anaerobic treatment of landfill leachate from incineration plants indicate that the Ca²⁺and Mg²⁺concentrations are 15 mmol/L,the overall operation effect of the reactor is the best,at this time,the concentration of coenzyme F420 and the COD removal efficiency of the effluent reach the highest;The pH value of the effluent decreases with the increase of Ca²⁺and Mg²⁺concentration;MLSS increases with the increase of Ca²⁺and Mg²⁺concentration in the influent,MLVSS and MLSS/MLVSS increase with the increase of Ca²⁺and Mg²⁺concentration when the Ca²⁺and Mg²⁺concentration of the influent is less than 15 mmol/L,and increase at 15 mmol/L reached the highest values of 11644 mg/L and 0.69 respectively,and then showed a decreasing trend with the increase of Ca²⁺and Mg²⁺concentrations.?3?Three-dimensional excitation emission matrix fluorescence spectroscopy was used to study the dissolved organic matter?DOM?in reactor effluent,the research results show that the water solubility in organic fluorescent material basically has 3 kinds,The addition of Ca²⁺and Mg²⁺had no effect on the types of fluorescent substances of dissolved organic matter in the effluent of the reactor,but significantly changed the intensity of fluorescence peak,When the concentration of Ca²⁺and Mg²⁺is relatively low??15mmol/L?,the peak intensity of fluorescence of proteins like tryptophan and tyrosine protein shows a decreasing trend.?4?The chemical method,combined with 3D-EEM and Fourier transform infrared spectroscopy,was used to study the effects of substances and functional groups on the composition of extracellular polymers,the research results showed that the chemical detection results showed that the increase of Ca²⁺and Mg²⁺concentration would cause a significant increase in the total amount of extracellular polymer in anaerobic activated sludge.The total amount of extracellular polymer in anaerobic activated sludge under the action of Ca²⁺and Mg²⁺at different concentrations was 62.50,64.69,68.21,68.61,76.40,78.70,83.17,87.92 and 113.69 mg/gVSS,respectively.The influence of Ca²⁺and Mg²⁺concentration on PN content was much higher than PS.When the concentration of Ca²⁺and Mg²⁺increased from 0 mmol/L to 100 mmol/L,PN content increased from 46.60mg/gVSS to 87.64 mg/gVSS,and PS content increased from 15.89 mg/gVSS to 26.04mg/gVSS.The results of detection of extracellular polymer by 3D-EEM spectrum showed that the addition of Ca²⁺and Mg²⁺did not change the type of fluorescence peak,there are mainly 5 fluorescence peaks in the extracellular polymer of anaerobic reactor,and the concentration of Ca²⁺and Mg²⁺has a great influence on the intensity of the fluorescence peak.Among them,the fluorescence peak of fulic acid and the coenzyme F₄₂₀ both show a trend of increasing first and then decreasing with the increase of the concentration of Ca²⁺and Mg²⁺in the influent water.In Fourier transform infrared spectroscopy results show that as the change of feed concentration of Ca²⁺,Mg²⁺amide I C=O stretching vibration absorption peak and protein secondary structure of the C=O stretching vibration peak appeared obvious deviation,polysaccharides of O-H or C-O vibration absorption peak also there is an obvious difference,When Ca²⁺and Mg²⁺were added into the water,the absorption peak of sulfur-containing phosphorous group appeared relative to that of Ca2+and Mg²⁺without the addition of Ca²⁺and Mg²⁺.With the increase of Ca²⁺and Mg²⁺concentration in the water,the intensity of the absorption peak gradually weakened and disappearedHigh concentration of Ca²⁺and Mg²⁺in landfill leachate in incineration plant is a difficult problem in anaerobic biological treatment of leachate.This study on the effects of Ca²⁺and Mg²⁺on effluent yield and EPS in the anaerobic biological treatment of landfill leachate in incineration plants is the key to solve the biological treatment of leachate,which has certain practical significance and scientific value.Figure[20]Table[7]Reference[110]...