Biosolids Dewatering Facilities Odor Control at the Los Angeles County Sanitation Districts' Joint Water Pollution Control Plant

The Los Angeles County Sanitation Districts operates one of the largest biosolids dewatering facilities in the United States at its Joint Water Pollution Control Plant. This facility, which produces over 1300 wet tons/day of biosolids, includes structures and equipment such as sludge storage wet wells, centrifuges, open belt conveyors, biosolids storage silos, and truck loading stations. The Joint Water Pollution Control Plant was originally sited in a rural setting but with extensive population growth over the last few decades it is now close to residential neighborhoods, large retail stores and several major thoroughfares. Due to the plant's location there is both public and regulatory pressure to assure that no biosolids odors are detected beyond the fenceline. Odor control at the biosolids dewatering facility is a significant undertaking due to the very odorous compounds that must be treated and because many of the processing facilities are large and uncovered, which makes ventilation difficult. To address this problem and come up with a solution, an extensive odor study was conducted. The odor study analyzed the different sources of odors from the biosolids dewatering facility, rated the odor sources by the use of odor panel analyses and used the odor panel results in atmospheric dispersion modeling to estimate off-site odors. Based upon the results of the atmospheric dispersion modeling a two stage approach is being used to control biosolids odors. The first stage of the odor control project is controlling odors from several of the sources that were identified as having a potential to produce significant off-site odors. The controls include using temporary covers, ventilation systems and modular biofilter units to treat the odorous air. The second phase of odor control consists of construction of a permanent odor control system for all the significant odor sources. The permanent system will include covers on conveyance systems, sludge silos, containment of a truck loading station, ventilation of the covered and contained processes and treatment of the ventilated air by two large biofilter units that will handle a combined air flow of 175,000 cfm.