Characterizing Bloom Biosolids: Microbial Community and Plant Growth.

Biosolids are rich in nutrients and organic matter, and are known to improve and maintain productive soils and stimulate plant growth. Blue Plains Resource Recovery Facility’s (BPRRF) of District of Columbia (DC) recent installation of a thermal hydrolyser from Norwegian company – CAMBI, the first of its kind in the USA, has made possible the production of Class A biosolids in DC, named Bloom^®. Using laboratory and greenhouse experiments, we have investigated the beneficial properties of Bloom for soil and plant health. We have examined Bloom at two stages, Fresh or Cured, for the presence of functional genes that would indicate the presence of microbes capable of improving plant growth. Bloom was screened for Ammonia Oxidizing Bacteria (AOB) and Archaea (AOA), N fixers, and Ureases carrying organisms. So far, we found that both Fresh and Cured Bloom have AOB communities. However, Cured Bloom biosolids have a larger gene copy number of AOB than Fresh Bloom, which means that they have a larger community of AOB to perform the conversion of ammonia to nitrite. Additionally, we have conducted greenhouse experiments to determine how Bloom effects the rate of plant growth. Soil mixes of fertilizer, Bloom, and compost, were used to grow tomatoes, cucumbers, and soybeans. Plant parameters were measured every week. We found that cucumbers and soybeans grow taller and have higher leaf and stem counts when Bloom® is present. A 1-month N mineralization experiment will also be conducted to study Bloom’s N cycling after the growing period. This project will inform BPRRF and the DC community how Bloom® performs in soil mixes and will add to the information needed to realize the value of properties that are found in Class A biosolids produced from a CAMBI system.