Study On Treatment Of Catalyst Ammonia-Contained Waste Water With Short-Term Nitrification/De-nitrification Microbial Technology

This article is aiming at the treatment of waste water of low ammonia/nitrogen content produced in the course of catalyst production by employing a short-term nitrification /de-nitrification technology and the alkali dregs-contained waste water from refinery is taking as an organic carbon source for treating the waster water with de-nitrification; meanwhile, the study on its mechanism and process is carried out to provide a basis for commercialized application.For the work both A/O reactor and SBR reactor are respectively employed in the study of degradation process of both ammonia/nitrogen-contained waste water and waste lye during the nitrification process. In SBR reactor a short-term nitrification/de-nitrification bio-N2-removal process is implemented taking simulated waste water with the reaction temperature controlled at 25±1℃,pH in 7.5-8.5 and DO concentration less than 0.5mg/L, under these conditions the initial concentration of ammonia/nitrogen is 1000mg/L, its nitrosation rate always kept at over 98% and in discharged nitrified water the concentration of NO3-N below 5.0mg/L and of ammonia/nitrogen below the detection limit, this is meeting the short-term nitrification/de-nitrifications process.With the determination of organic ingredients in waste lye by GC-MS it is found that the main component is aromatic compound, in which phenols amounting to 84.11%, anilines to 7.79% and sulfide to 1.31%.The alkalinity of waste lye is of 50000mg/L, with B/C=0.29 the biodegradability is poor. In SBR reactor a batch-wise addition of waste lye as a carbon source for de-nitrification is used and under the condition of COD concentration in supplied water being 1200mg/L and the concentration of ammonia/nitrogen in the reactor being 300mg/L an operation of an aeration for 4 hours and a non-oxygen of 2 hours is proceeded to enable the concentration of ammonia/nitrogen in the final discharged water to be below the detection limit and the concentration of total nitrogen in discharged water,1.69mg/L.The removal effect of both organic sulfur and volatile phenol in the running of nitrification and de-nitrification process is equally effective; in SBR intermittent reactor the removal rate of both organic sulfur and volatile phenol reaches respectively 92.0% and 93.9%; in A/O continuous reactor the removal rate of both organic sulfur and volatile phenol reaches respectively 93.9% and 99.6%. The above shows that such pollutants as volatile phenol and organic sulfur contained in waste lye can be removed as an organic carbon source required in ammonia/nitrogen de-nitrification degradation. In the same aeration unit pH value has a 0.07 drop during the aeration whereas it has a 0.05 rise during the non-oxygen stage. With the change of pH value in aeration and non-oxygen stages it may be seen that the alkalinity generated during de-nitrification process is insufficient to make up for the consumption of alkalinity in nitrification stage, it is about a half of the alkalinity consumption in nitrification stage. By taking the alkalinity of waste lye as that for nitrification may make up for a lack of alkalinity in the short-term nitrification/de-nitrification process to reach a co-treatment of waste lye and high ammonia/nitrogen waste water.A/O system covers two reactors respectively for nitrification reaction and de-nitrification reaction; in the nitrification reaction pond the alkalinity of waste lye is used to completely remove ammonia/nitrogen of 300 mg/L within 24 hours from the supplied water, and the nitrosation rate of over 90% may be achieved as maximum. In de-nitrification reaction pond NOx-N can be completely degraded to below the detection limit within 8 hours to realize a short-term nitrification/de-nitrification process for a continuous flow.An important influencing factor in the control of either a short-term or a complete nitrification is how to control the concentration of dissolved oxygen. Experiments confirm that during the short-term nitrification stage the concentration of DO must be controlled at below 0.5 mg/L, but a high nitrosation rate may be maintained. However, the concentration of DO controlled at above 2.0 mg/L in a traditional aeration pond may lead to a complete nitrification.The identification of 16S rRNA Gene Clone Library shows that the bacteria of Nitrosomonas group in activated sludge from a short-term nitrification/de-nitrification is a dominant type and amounting to about 50% in the entire library, particularly among which the strain FXHWN-14 with its similarity to the strain Nitrosomonas europaea ATCC25978 being 99% and the strain FXHWN-29 with its similarity to the strain Nitrosomonas halophila being 99% are taking as the main, both the strains, provided with a stronger short-term nitrification ability, are classified as ammonia oxidizing bacteria (AOB) capable of oxidizing ammonia to nitrite.This basic study and pilot test take that the efficiency in the treatment of ammonia/nitrogen by the short-term nitrification/de-nitrification process is high, operation simple and convenient and running cost low meeting the needs for an integrated treatment of low-concentrated ammonia/nitrogen sewage from present domestic catalyst producers and sewage from oil-refining and chemical complex.