NH3 Loading Research Articles

Surface Limestone Application Increases Ammonia Volatilization from Goat Urine in Abandoned Pastures

ABSTRACT Concentrated application of nitrogen (N) resulting from urine deposition by livestock can cause nitrate pollution of ground water. Use of goats (Capra hircus) at high stocking densities to clear unwanted shrubs from abandoned pasture during renovation increases the probability of multiple depositions of urine. We hypothesized that applying limestone early in the pasture restoration process would favor ammonia (NH3) volatilization. This would increase the area over which N was distributed and reduce the potential for localized nitrate pollution, although atmospheric NH3 loading would be increased. To study the effect of surface limestone application on NH3 generation, we collected 32 soil profile columns with intact vegetation from an abandoned pasture in southern WV. Urine was applied 18 weeks after surface application of 6720 kg/ha (6000 lb/ac) limestone. Columns received one, two, or three applications of 100 mL goat urine, adding a total of 9.8, 31.7, and 66.4 g/m2 N, respectively. The amount of NH3 increased markedly with increased urine application. Ammonia production decreased exponentially with time after each addition. Overall, limed columns generated 132% more NH3 than unlimed columns. Dry matter production was highest in the treatment receiving two urine applications and lowest in the control receiving no urine. Three urine applications damaged plants; this scorching was correlated with amount of NH3 generated. With time, plant cover in damaged treatments recuperated, with broadleaf plants tending to replace grass. Surface limestone application increased the amount of urine N transformed to NH3 gas, especially where there were multiple urine deposits.

Hydrogen sulfide effects on ammonia removal by a biofilter seeded with earthworm casts.

Ammonia (NH3) removal efficencies were evaluated when hydrogen sulfide (H2S) and NH3 in binary mixture gases were supplied to a ceramic biofilter seeded with earthworm (Lumbricus terrestris) casts. The effect of inlet H2S concentration and space velocity (SV) on the removal of NH3 was investigated after the acclimation of the biofilter with NH3 gas. When NH3 was singly supplied to the biofilter, NH3 removal was maintained at almost 100% until inlet NH3 concentration was increased up to 600 microL L(-1) and SV up to 330 h(-1), at which the elimination capacity of NH3 was 148 g N m(-3) h(-1). When H2S was supplied simultaneously, however, the accumulation of toxic sulfide ions showed dual effects on NH3 removal efficiencies. First, no effects were observed at inlet H2S loading below 60 g S m(-3) h(-1); however, inhibition by H2S at higher loading was observed above 60 g S m(-3) h(-1). The point at which loading achieved a maximum of more than 99% NH3 removal efficiency was 139 g N m(-3) h(-1), when inlet H2S concentration was held under 100 microL L(-1), but it dropped to 76 and 30 g N m(-3) h(-1) when the inlet H2S concentration increased to 220 and 460 microL L(-1), respectively. The critical points of inlet H2S loading that guaranteed over 99% NH3 removal were determined as 100, 100, 60, and 40 g S m(-3) h(-1) at inlet NH3 concentrations of 100, 200, 400, and 600 microL L(-1), respectively. Inlet NH3 loading had synergic effects of increasing the inhibition of inlet H2S loading on the NH3 removability of the biofilter.

Regeneration of a Compost Biofilter Degrading High Loads of Ammonia by Addition of Gaseous Methanol

The long-term stability of a biofilter loaded with waste gases containing NH3 concentrations larger than 100 ppmv was studied in a laboratory-scale compost reactor. At an empty bed residence time (τ) of 21 sec, elimination capacities of more than 300 g NH3/m3/day were obtained at elimination efficiencies up to 87%. Because of absorption and nitrification, almost 80% of the NH3-N eliminated from the waste gas could be recovered in the compost as NH4+-N or NO2 −/NO3 −-N. The high elimination capacities could be maintained as long as the NH4+/NOx concentration in the carrier material was less than 4 g NH4+/NOx −-N/kg wet compost. Above this critical value, osmotic effects inhibited the nitrifying activity, and the elimination capacity for NH3 decreased. To restore the biofilter performance, a carbon source (methanol) was added to reduce NH4+/NOx − accumulated in the compost. Results indicate that methylotrophic microorganisms did convert NH4+/NOx − into biomass, as long as the NO3 − content in the compost was larger than 0.1 g NO3 −-N/kg compost. Removal efficiencies of CH3OH of more than 90% were obtained at volumetric loads up to 11,000 g CH3OH/m3/day. It is shown that addition of CH3OH is a suitable technique for regenerating the compost material from osmotic inhibition as a result of high NH3 loading. The biofilter was operated for 4 months with alternating loading of NH3 and CH3OH.

Removal of Ammonia from Contaminated Air by Trickle Bed Air Biofilters

ABSTRACT A trickle bed air biofilter (TBAB) was evaluated for the oxidation of NH3 from an airstream. Six-millimeter Celite pellets (R-635) were used for the biological attachment medium. The efficiency of the biofilter in oxidizing NH3 was evaluated using NH3 loading rates as high as 48 mol NH3/m3 hr and empty-bed residence times (EBRTs) as low as 1 min. Excess biomass was controlled through periodic backwashing of the biofilter with water at a rate sufficient to fluidize the medium. The main goal was to demonstrate that high removal efficiencies could be sustained over long periods of operation. Ammonia oxidation efficiencies in excess of 99% were consistently achieved when the pH of the liquid nutrient feed was maintained at 8.5. Quick recovery of the biofilter after backwashing was observed after only 20 min. Evaluation of biofilter performance with depth revealed that NH3 did not persist in the gas phase beyond 0.3 m into the depth of the medium (26% of total medium depth).

Comparison between Supported Gas Membrane Process and Supported Liquid Membrane Process for the Separation of NH3 from Aqueous Media Containing NH3 and CO2

A comparison between the hollow fibre supported gas membrane (SGM) process and the hollow fibre supported liquid membrane (SLM) process for the separation of NH3 from aqueous solutions containing NH3 and CO2 was performed. The experimental data as well as the model simulation demonstrate that the SLM process can remove NH3 from aqueous solutions of NH3 and CO2 at a higher rate than the SGM process when the NH3 loading is low or the ratio of NH3 to CO2 is low. This study suggests that the proper combination of the SGM process and the SLM process can strip NH3 more effectively from aqueous solutions containing NH3 and CO2.