Emissions, measurement, and control of odor in livestock farms: A review.

Odor emissions from intensive livestock farms have attracted increased attention due to their adverse impacts on the environment and human health. Nevertheless, a systematic summary regarding the characteristics, sampling detection, and control technology for odor emissions from livestock farms is currently lacking. This paper compares the development of odor standards in different countries and summarizes the odor emission characteristics of livestock farms. Ammonia, the most common odor substance, can reach as high as 4100 ppm in the compost area. Sampling methods for point and area source odor emissions are introduced in this paper, and odor analysis methods are compared. Olfactometers, odorometers, and the triangle odor bag method are usually used to measure odor concentration. Odor control technologies are divided into three categories: physical (activated carbon adsorption, masking, and dilution diffusion), chemical (plant extract spraying, wet scrubbing, combustion, non-thermal plasma, and photocatalytic oxidation), and biological (biofiltration, biotrickling, and bioscrubbing). Each technology is elucidated, and the performance in the removal of different pollutants is summarized. The application scopes, costs, operational stability, and secondary pollution of the technologies are compared. The generation of secondary pollution and long-term operation stability are issues that should be considered in future technological development. Lastly, a case analysis for engineering application is conducted.

[Removal of Hydrogen Sulfide Produced in a Municipal WWTP Using a Biotrickling Filter with Polypropylene Rings as the Packing Material and Microbial Community Analysis].

Under transient conditions, a biotrickling filter was developed to treat gaseous H2S produced from the fine-grid reservoir of a municipal wastewater treatment plant (WWTP) with AAO excess sludge as the inoculum and polypropylene rings as the packing material. The start-up process and steady-state operation of the biotrickling filter were studied. With an empty bed retention time of 14 s, an ambient temperature of 7.8-32.5℃, and an inlet concentration of 2.02-319.19 mg·m-3, an average removal efficiency of 91.8% was achieved with a maximum H2S elimination capacity of 78.37 g·(m3·h)-1. Over a 247-day period, the pressure drop across the biotrickling filter was maintained at 96 Pa·m-1. Microbial analysis using high-throughput sequencing technology showed a variation in the microbial community during the experiment; the Shannon index dropped from 4.99 to 3.75, and the functional genera Pseudomonas and Thiobacillus were identified as good performers in the biotrickling filter system. These results indicate that the application of AAO excess sludge as an inoculum for biotrickling filters is feasible for effective H2S removal. A steady pressure drop was achieved using polypropylene rings as the packing material. The diversity of the microbial community showed a downward trend when exposed to H2S, but the elimination capacity could be increased.