Biodegradation Characteristics of Nitrogen-Containing Compounds Used for Semiconductor and Optoelectrical Industries
Semiconductor and optoelectrical industries are among the major high-technological enterprises in Taiwan. Many nitrogen-containing compounds such as monoethanol amine (MEA), 1-methyl-2-pyrrolidinone (NMP), 1-amino-2-propyl alcohol (APA) and hexamethylene disilazane (HMDS) are used in both manufacturing processes. These compounds may release to environments from waste gas or water sources and become environmental pollutants if not properly treated. The main purpose of this research was to investigate the biodegradation characteristics of the four compounds.
The research was performed by using a 5-L sequencing batch reactor operated at a cycling time of 24 hrs that included a filling time of 0.5 hr, an aeration and reaction time of 21 hrs, a setting time of 2 hrs, and a drawing time of 0.5 hr. The reaction conditions were as follows for the activated sludge in the reactor: MLSS (mixed liquor suspended solids) = 2000-3000 mg/L, pH = 6.8-7.2, aeration intensity = 0.46 L air/(L liquor. min), F/M (food-to-microorganism ratio) = 0.2-0.5 kg COD/(kg MLSS. Day), and C0 (initial concentration of the target compound in the mixed liquor) = 100-800 mg/L.
Results demonstrate that above around 80% of all the four compounds were degraded within the aeration time of 21 hrs, and the organic nitrogen was converted to NH3-N, NO2¡Ð-N, NO3¡Ð-N, N2,and biomass-N.
For MEA, above 10 % of the NH3-N hydrolyzed from the compound was nitrified for loadings of less than 0.05 kg MEA-N/m3.day, and no nitrification was observed for loadings of above 0.20 kg MEA-N/m3.day. Approximate 3% of MEA-N was converted to biomass-N and the average nitrogen content in the sludge was 4.25%.
With regards to NMP, around 5, 73-83, and 14-24% of the nitrogen was converted to NH3-N+NO2¡Ð-N+NO3¡Ð-N, N2, and biomass-N, respectively, and the average nitrogen content in the sludge was 5.6%.
As for the biodegradation of APA, there occurred a filamentous sludge-bulking phenomenon when C0 = 400 or 800 mg/L. With C0 increased from 200 to 800 mg/L, there was an increasing rate of ammonia formation and decreasing rate of nitrification. For the compound, around 9, 74, and 13% of the nitrogen was converted to NO2¡Ð-N, N2, and biomass-N, respectively, at a loading of 0.0358 kg APA-N/m3.day. The conversions became 12, 66, and26%, respectively, for NO2¡Ð-N, N2, and biomass-N with the loading increased to 0.0716 kg APA-N/m3.day. The average nitrogen content in the sludge was 4.9%.
HMDS was biologically degraded in the emulsion state with the help of surfactants Tween 80 and Span 80. With C0 increased from 200 to 800 mg/L, there was an increasing nitrification rate and nearly constant ammonia nitrite formation rates. Above 90% of HMDS-N was converted to N2 and a few of it to biomass-N. The average nitrogen content in the sludge was around 4.5%.
Advisor:Shin- Mei Jinan; Yang-Lei; Jou-Min Shian
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:nmp apa mea hmds
Date of Publication:06/22/2003