Analysis of effects and factors linked to soil microbial populations and nitrogen cycling under long-term biosolids application.

Information about impacts of long-term biosolids application on soil microbial populations and functional groups and N cycling is important for evaluating soil health and agroecosystem sustainability under long-term biosolids application. Mine spoil plots received annual biosolids application from 1973 to 2010 at low (16.8 Mg ha-1 yr-1), medium (33.6 Mg ha-1 yr-1), and high rates (67.2 Mg ha-1 yr-1). A no-biosolids control received chemical fertilizer at the agronomic rate. Soil samples were collected in three seasons per year spanning 2003-2005 for measuring soil moisture, pH, soil organic C (SOC), total and extractable heavy metals (Cd, Cu, Ni, Zn), NO3-, N mineralization potential (NMP), microbial biomass C (MBC), and populations of three N-cycling bacteria (NCB) groups: ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and denitrifying bacteria (DNB). Soil samples were collected again in 2008 and 2010 for quantifying total and extractable heavy metals, and in 2018 (eight years after biosolids applications ended) for measuring SOC, MBC, NMP, and microbial respiration. During 2003-2005, mean MBC was 315, 554, 794, and 1001 mg kg-1 in the control, low, medium, and high biosolids treatments, respectively. Populations of NCB did not differ among treatments. Biosolids application increased total and extractable metal concentrations but the effect of biosolids rates were much lower on extractable than total concentrations. Soil extractable Cd and Cu concentrations decreased from medium to high applications, likely due to complexing with biosolids organic matter. Partial least squares regression analysis identified a strong positive effect on MBC of SOC and a weak negative effect of Cu, explaining the strong net positive effect of biosolids on MBC. In 2018, the medium and high biosolids treatments maintained higher SOC, MBC, NMP, and microbial respiration than the control. This study provided further evidence that long-term biosolids application has positive effects on soil microbes that persist for years after ending application.

Long-term biosolids planning with an operational mega reservoir for combined sewer overflow-impacted stormwater capture.

The Metropolitan Water Reclamation District of Greater Chicago adopted the Tunnel and Reservoir Plan (TARP) to reduce combined sewer overflow (CSO) events in the Chicago region. The Thornton Composite Reservoir (TCR) became operational in 2015 providing an additional 30 million m3 of CSO-impacted stormwater capacity. In the United States, no other mega reservoirs are in operation to provide as a reference to study the long-term impacts of biosolids operations in water resource recovery facilities. The mean daily volume pumped from the Calumet TARP system to the Calumet Plant increased 144-238 m3 from 2012-2014 to 273-360 m3 from 2016-2018. Overall annual digester feed solids for the 2016-2018 post-TCR period were 28,182 Mg, which was 11 percent less than the mean for the 2012-2014 period of 31,745 Mg. Annual digester draw solids for the 2016-2018 post-TCR period were 19,422 Mg, which were 4 percent less than the 2012-2014 pre-TCR period mean of 20,190 Mg. This paper demonstrated a decrease in digester feed loading to the Calumet Plant and, ultimately, a decrease in digester draw solids with an overall increase in plant and TARP flow in the years following operation of the TCR for the capture and treatment of CSO-impacted stormwater. PRACTITIONER POINTS: Reservoirs capturing combined sewer overflow-impacted stormwater improve water quality of local waterways. Mega reservoirs may impact solids loading to water resource recovery facilities. Hydraulic loading to water resource recovery facilities may be substantial with mega reservoirs.

A reduction in triclosan and triclocarban in water resource recovery facilities' influent, effluent, and biosolids following the U.S. Food and Drug Administration's 2013 proposed rulemaking on antibacterial products.

Pharmaceutical and personal care product compounds (PPCPs) comprise a large and diverse group of chemical compounds, including prescription and over-the-counter drugs and cleaning agents. Although PPCPs in the effluent and biosolids of water resource recovery facilities (WRRFs) are currently not regulated, public interest has led the Metropolitan Water Reclamation District of Greater Chicago to monitor for 11 PPCPs in the influent, effluent, and biosolids at its seven WRRFs. In 2016, the U.S. Food and Drug Administration (FDA) issued a final rule establishing that 19 specific ingredients, including triclosan and triclocarban, were no longer generally recognized as safe and effective, which prohibits companies from marketing soaps as antibacterial if they contain one or more of these ingredients. It was presumed that since the proposed rulemaking in 2013, manufacturers began to remove these active ingredients from their products. Annual monitoring of 11 PPCPs from 2012 to 2017 demonstrated a 71% decrease in triclosan and 72% decrease in triclocarban in per capita influent loading into seven WRRFs. There was a 70% decrease in triclosan and 80% decrease in triclocarban concentrations in biosolids. These declines suggest the FDA rule for the reduction in use of these compounds was effective and resulted in manufacturers removing these ingredients from their products. PRACTITIONER POINTS: Reduction in triclosan and triclocarban per capita influent loading observed from 2012 to 2017. Reduction in triclosan and triclocarban biosolids loading observed from 2012 to 2017. 2016 FDA rulemaking on antimicrobial soaps was effective in removing triclosan and triclocarban from these products. Positive impact on quality of biosolids land applied to farmland.