Biological indicators for assessment of the nitrification activity: using a full-scale biological nitrogen removal process for coke wastewater as an example

Abstract

Biological wastewater treatment plant (WWTP) is an economic way commonly used for nitrogen removal in coke wastewater which contained phenolic organic compounds and inorganic constituents like cyanides thiocyanate and ammonia When untreated wastewater released to environment these pollutants may hurt to ecology and caused deterioration of water quality in river In order to assess the function of biological WWTP many indicators from molecular techniques could help us to make decisions including quantity of genes (DNA level) expression of genes (RNA level) the microorganism community etc During nitrification ammonia-oxidizing bacteria (AOB) can obtain energy by oxidizing ammonia to nitrite As one of the important functional gene for ammonia oxidation amoA is involved in the reaction converting ammonia to hydroxylamine Biological treatment for coke wastewater requires serial nitrogen removal process e g nitrification and denitrification and organic chemical degradation Among them nitrification is relatively sensitive due to the slow growth rate of autotrophic microorganism and can be easily inhibited In order to reduce the frequency of abnormalities on nitrification in the coking WWTP the routine assessment of nitrification activity is necessary The objective of this research is to develop molecular biological indicators such as monitoring of amoA mRNA for nitrification activity in full-scale WWTP and verify its applicability by incorporating water quality As for the molecular indicators quantitative PCR (qPCR) was used to quantify the genes of amoA nitrobacter 16S rRNA and nitrospira 16S rRNA while terminal restriction fragment length polymorphism (T-RFLP) and sequencing was used to analysis AOB community composition By monitoring the water quality in nitrification tank of the full-scale WWTP it could be found that ammonia removal efficiency decreased from 72% to 13% when increasing ammonia concentration from 38 mg N/L to 104 mg N/L AOB population and amoA mRNA expression maintained stable but AOB community change along with the elevation of influent ammonia concentration For example Nitrosomonas eutropha-like AOB strain with T-RF F491/R491 was domesticated after the adaptation of high concentration of ammonia Batch results indicates that nitrification might be reduced by 400 mg/L of phenol through competitive inhibition though it could be recovered rapidly after phenol degradation and by 175 mg/L of quinoline due to the suppression on amoA mRNA which leads to the severe decrease in the specific nitrite production rate In summary monitoring the expression pattern and strength of amoA mRNA in nitrification batch tests could help us to assess the nitrification activity and clarify the inhibitors and its mechanism showing that molecular indicator could be a useful tool to evaluate biological activity in the full-scale WWTP

Date of Award	2019
Original language	English
Supervisor	Liang-Ming Whang (Supervisor)