Interaction of acrylonitrile vapors on a bench scale biofilter treating styrene-polluted waste gas streams

Considering concurrent use of styrene and acrylonitrile as raw materials in the production of synthetic resins and plastic and their associated differences in physiochemical properties and biodegradability, our experiments were conducted in a three-stage downflow bench-scale biofilter to study the potential suppressive effects of acrylonitrile on styrene removal. A Mixture of yard waste compost and shredded plastics and activated sludge was used as bed media. Gas phase concentration of styrene and acrylonitrile was determined via gas chromatographic analysis. Under steady-state conditions, maximum elimination capacity of styrene and acrylonitrile was 44 and 120 g/m[3] h, respectively. The effect of moisture was very significant in reducing the specific adsorptive capacity [microg/g of bed media] of styrene and acrylonitrile. The bed media with 60% moisture content lost styrene absorption capacities by more than one order of magnitude when compared to dry media. The existence of water increased the absorption capacity of medium for acrylonitrile about 95%. Styrene elimination capacity of the biofilter during co-treatment was less as compared to pure styrene biodegradation indicating the likelihood of inhibitory kinetics. Introduction of acrylonitrile into the air stream reduced elimination capacity of styrene to 103 g/m[3] h. The adverse impact on removal rate of acrylonitrile due to the presence of styrene in the gas stream was minimal. Carbonequivalent removal for the system amounted to about 85 g C/m[3] h at empty bed retention time of 120 s

Fate of intermediate biodegradation products of triethyl amine in a compost-based biofiltration system

Biofiltration of Triethylamine [TEA] vapor used as a catalyst in casting operations was evaluated in this study. The unit consisted of a 6-L three-stage biofilter containing a mixture of compost and wood chips [40:60 v/v] as the filter medium. Seed microbial population from municipal activated sludge was acclimated for a period of three weeks prior to the actual experimental runs. In the startup period, high pH values up to 10 was observed due to alkaline nature of TEA and inadequate formation of biofilm and low overall biodegradation. Steady increase of organic-N concentration along with gradual upward trend of pressure drop indicated sound establishment of microbial population. Operational parameters studied included loading rate [6-116 g/m[3]/h], hydraulic detention times [40-60 s], temperature [30 +/- 1°C], and humidity [50-55%]. Results indicated effluent ammonia concentrations meeting standards of 25 ppm can be obtained after 2.5 months of operation. Optimal organic loading rates [OLRs] of 90 +/- 14 g/m3/h for Hydraulic Retention Time [HRT] value of 48 s were suggested. Under these conditions, elimination capacity of 71 +/- 3 g/m3/h and removal efficiency 81 +/- 14% were achieved. Mass balance was performed on different forms of nitrogen products for a constant inlet concentration of 180 ppm TEA with a relatively stable removal efficiency of about 90% maintained for over a month. Both liquid [leachate] and gas [different sections, inlet, and outlet] phase measurements were made for the purpose of performing calculations. Ammonium- N and Nitrate-N were dominant in the first and third sections of the reactor, respectively. Cumulative TEA-N mass balance over a 2-month period indicated an equal proportion breakdown into ammonia- N, nitrate-N, and ammonium and organic-N. The fact that up to 30% of TEA-N could not be accounted for in the leachate and gas measurements can be attributed to incorporation into the cellular constituents

Effects of operational conditions on the performance of Triethylamine Biofiltration

Nitrogen compounds such as triethylamine are odorants generally found in chemical plants and foundries in which cold-box cores are made. In this study, the efficiency of biofiltration of triethylamine [TEA] vapor was evaluated. Experiments were conducted in two 6-L biofilters arranged in three stages and packed with inoculated compost - wood chips [40:60v/v] as the filter medium. The seed inoculum was obtained from municipal activated sludge. Tests were made to compare effects of initial temperature [30-/+1°C, biofilter A] and [23-/+2 °C, biofilter B] on the performance of the biofilter. TEA elimination rate pattern was evaluated by changing loading rates [6-138 gm-3h-1 and hydraulic retention times [40-60 s] while operating at constant temperature and humidity at 50-55%. Results showed that organic loading rates [OLR] of up to 114.4 gin-3h-1 [biofilter A] and 90.56 gin-3h-1 [biofilter B] could be handled without any apparent indication of maximum elimination capacity and substrate inhibition. The elimination capacity of biofilters could reach up to 72 gm-311-1[biofilter A] and 613 gm-3h [biofilter B]. When the loading of TEA exceeded the critical values, substrate inhibition occurred and the elimination capacity decreased. However, the requirement of keeping the pressure drop below 4 cm water gauge per meter of bed height to avoid operational problems warranted lower than maximum capacity operation. The optimal OLR values of 90-114 gm3h-1 are suggested for hydraulic retention time value of 48 s and temperature of 30-/+1°C. Under these conditions, elimination capacity of 71-/+3 gm-3h-land removal efficiency of 81-/+14% was achieved