Effect of Pyrolysis on the Removal of Antibiotic Resistance Genes and Class I Integrons from Municipal Wastewater Biosolids

Wastewater biosolids represent a significant reservoir of antibiotic resistance genes (ARGs). While current biosolids treatment technologies can reduce ARG levels in residual wastewater biosolids, observed removal rates vary substantially. Pyrolysis is an anoxic thermal degradation process that can be used to convert biosolids into energy rich products including py-gas and py-oil, and a beneficial soil amendment, biochar. Batch pyrolysis experiments conducted on municipal biosolids revealed that the 16S rRNA gene, the ARGs erm(B), sul1, tet(L), tet(O), and the integrase gene of class 1 integrons (intI1) were significantly reduced at pyrolysis temperatures ranging from 300–700 °C, as determined by quantitative polymerase chain reaction (qPCR). Pyrolysis of biosolids at 500 °C and higher resulted in approximately 6-log removal of the bacterial 16S rRNA gene. ARGs with the highest observed removals were sul1 and tet(O), which had observed reductions of 4.62 and 4.04-log, respectively. Pyrolysis reaction time had a significant impact on 16S rRNA, ARG and intI1 levels. A pyrolysis residence time of 5 minutes at 500 °C reduced all genes to below detection limits. These results demonstrate that pyrolysis could be implemented as a biosolids polishing treatment technology to substantially decrease the abundance of total bacteria (i.e., 16S rRNA), ARGs and intI1 prior to land application of municipal biosolids

Pyrolysis of Wastewater Biosolids Significantly Reduces Estrogenicity

Most wastewater treatment processes are not specifically designed to remove micropollutants. Many micropollutants are hydrophobic so they remain in the biosolids and are discharged to the environment through land-application of biosolids. Micropollutants encompass a broad range of organic chemicals, including estrogenic compounds (natural and synthetic) that reside in the environment, a.k.a. environmental estrogens. Public concern over land application of biosolids stemming from the occurrence of micropollutants hampers the value of biosolids which are important to wastewater treatment plants as a valuable by-product. This research evaluated pyrolysis, the partial decomposition of organic material in an oxygen-deprived system under high temperatures, as a biosolids treatment process that could remove estrogenic compounds from solids while producing a less hormonally active biochar for soil amendment. The estrogenicity, measured in estradiol equivalents (EEQ) by the yeast estrogen screen (YES) assay, of pyrolyzed biosolids was compared to primary and anaerobically digested biosolids. The estrogenic responses from primary solids and anaerobically digested solids were not statistically significantly different, but pyrolysis of anaerobically digested solids resulted in a significant reduction in EEQ; increasing pyrolysis temperature from 100 °C to 500 °C increased the removal of EEQ with greater than 95% removal occurring at or above 400 °C. This research demonstrates that biosolids treatment with pyrolysis would substantially decrease (removal \u3e 95%) the estrogens associated with this biosolids product. Thus, pyrolysis of biosolids can be used to produce a valuable soil amendment product, biochar, that minimizes discharge of estrogens to the environment

Pyrolysis of Dried Wastewater Biosolids Can Be Energy Positive

Pyrolysis is a thermal process that converts biosolids into biochar (a soil amendment), py-oil and py-gas, which can be energy sources. The objectives of this research were to determine the product yield of dried biosolids during pyrolysis and the energy requirements of pyrolysis. Bench-scale experiments revealed that temperature increases up to 500 °C substantially decreased the fraction of biochar and increased the fraction of py-oil. Py-gas yield increased above 500 °C. The energy required for pyrolysis was approximately 5-fold less than the energy required to dry biosolids (depending on biosolids moisture content), indicating that, if a utility already uses energy to dry biosolids, then pyrolysis does not require a substantial amount of energy. However, if a utility produces wet biosolids, then implementing pyrolysis may be costly because of the energy required to dry the biosolids. The energy content of py-gas and py-oil was always greater than the energy required for pyrolysis

Decay of escherichia coli in soil following the application of biosolids to agricultural land

The decay of Escherichia coli in a sandy loam soil, amended with enhanced and conventionally treated biosolids, was investigated in a field experiment following spring and autumn applications of sewage sludge. Control soils, without the application of biosolids, were also examined to determine the background indigenous populations of E. coli which are present in the environment. The survival of indigenous E. coli and populations of E. coli applied to soil in biosolids, is assessed in relation to environmental factors influencing pathogen-decay processes in soil

Soil and crop responses following application of biosolids-derived organomineral fertilisers to ryegrass (Lolium perenne L.) grown in pots

Biosolids-derived organomineral fertilisers (OMF) were produced using a novel technique reported in earlier studies. This technique enables addition of N and potash to biosolids granules to form a balanced NPK fertiliser. Two fertiliser products; OMF10 (10:4:4) and OMF15 (15:4:4), were formulated and tested in a glasshouse facility on pot-grown ryegrass in comparison with urea and biosolids granules at N application rates ranging from 0 to 300 kg ha-1. The aim of this research was to contribute to the understanding of nutrients management and dynamics in grass crops fertilised with OMF. The study focused upon dry matter yield (DMY) and crop responses to applied fertiliser, nitrogen use efficiency (NUE) and fertilisers’ effect on soil fertility. Results indicated that ryegrass responds linearly to application of OMF increasing DMY by about 2% to 27% compared with biosolids but to a lesser extent than urea (range: 17% to 55%). NUE was related to the concentration of readily available N in the fertiliser; urea and OMF showed significantly greater (P<0.05) N recoveries than biosolids (26% to 75%, and 19% to 29%, respectively). Total nitrogen in soil and SOM increased (P<0.05) depending on the concentration of organic-N in the fertiliser applied. DMY was lower but more sustained overtime in biosolids-treated pots. OMF application did not result in significant changes in soil extractable-P levels whereas for urea, it decreased significantly while it showed a significant increase in biosolids-treated pots, where soil-P Index changed from 5 to 6. In OMF-treated soil, soil P Index remained close to constant overtime thereby supporting the purpose of the formulations tested

Emerging Investigators Series: Pyrolysis Removes Common Microconstituents Triclocarban, Triclosan, and Nonylphenol from Biosolids

Reusing biosolids is vital for the sustainability of wastewater management. Pyrolysis is an anoxic thermal degradation process that can be used to convert biosolids into energy rich py-gas and py-oil, and a beneficial soil amendment, biochar. Batch biosolids pyrolysis (60 minutes) revealed that triclocarban and triclosan were removed (to below quantification limit) at 200 °C and 300 °C, respectively. Substantial removal (\u3e90%) of nonylphenol was achieved at 300 °C as well, but 600 °C was required to remove nonylphenol to below the quantification limit. At 500 °C, the pyrolysis reaction time to remove \u3e90% of microconstituents was less than 5 minutes. Fate studies revealed that microconstituents were both volatilized and thermochemically transformed during pyrolysis; microconstituents with higher vapor pressures were more likely to volatilize and leave the pyrolysis reactor before being transformed than compounds with lower vapor pressures. Reductive dehalogenation products of triclocarban and suspected dehalogenation products of triclosan were identified in py-gas. Application of biosolids-derived biochar to soil in place of biosolids has potential to minimize organic microconstituents discharged to the environment provided appropriate management of py-gas and py-oil

Ion Exchange for Nutrient Recovery Coupled with Biosolids-Derived Biochar Pretreatment to Remove Micropollutants

Wastewater, especially anaerobic treatment effluent, contains high ammonia nitrogen (NH4-N) and inorganic orthophosphate (PO4-P), which necessitate additional treatment to meet stringent discharge regulations. Ion exchange regeneration is a process that can be adopted for not only removing but also recovering nutrients. However, recovering nutrients by ion exchange from nutrient-rich effluents that also contain micropollutants (which typically pass through anaerobic treatment as well) may result in subsequent problems, since micropollutants could end up in ion exchange effluent, regenerant, or recovered fertilizer products. Micropollutant removal by a nonselective adsorbent, such as biosolids-derived biochar, before nutrient recovery processes would mitigate potential risks. The objective of this research was to evaluate the capability of biosolids-derived biochar as a pretreatment step for separating micropollutants from nutrient-rich water before ion exchange for nutrient recovery. In the presence of ammonium and phosphate, both pristine and regenerated biosolids-derived biochar could effectively adsorb triclosan (TCS) and estradiol (E2), and to a lesser extent, sulfamethoxazole (SMX) in batch sorption experiments. On the other hand, nutrient ions were not effectively adsorbed by biosolids-derived biochar. A continuous flow-through system consisting of columns in series filled with biochar, LayneRT, and then clinoptilolite was operated to test selective removal of micropollutants and nutrients in a flow-through system. The biochar column achieved more than 80% removal of influent TCS and E2, thereby reducing the chances of micropollutants being adsorbed by ion exchangers. Sulfamethoxazole removal through the biochar column was only 50%, indicating that biosolids-derived biochar would have to be optimized in the future for hydrophilic micropollutant removal. Influent nutrients were not effectively removed by the biochar column, but were captured in their respective selective ion exchanger columns. This research revealed that biosolids-derived biochar could be employed before ion exchange resins for removal of micropollutants from nutrient-rich water

Biochar from Pyrolysis of Biosolids for Nutrient Adsorption and Turfgrass Cultivation

At water resource recovery facilities, nutrient removal is often required and energy recovery is an ever-increasing goal. Pyrolysis may be a sustainable process for handling wastewater biosolids because energy can be recovered in the py-gas and py-oil. Additionally, the biochar produced has value as a soil conditioner. The objective of this work was to determine if biochar could be used to adsorb ammonia from biosolids filtrate and subsequently be applied as a soil conditioner to improve grass growth. The maximum carrying capacity of base modified biochar for NH3−N was 5.3 mg/g. Biochar containing adsorbed ammonium and potassium was applied to laboratory planters simulating golf course putting greens to cultivate Kentucky bluegrass. Planters that contained nutrient-laden biochar proliferated at a statistically higher rate than planters that contained biosolids, unmodified biochar, peat, or no additive. Nutrient-laden biochar performed as well as commercial inorganic fertilizer with no statistical difference in growth rates. Biochar from digested biosolids successfully immobilized NH3−N from wastewater and served as a beneficial soil amendment. This process offers a means to recover and recycle nutrients from water resource recovery facilities

Sand to Root Transfer of PAHs and PCBs by Carrots Grown on Sand with Pure Substances and Biosolids Amended Sand

A study on behaviour of trace organic compounds (Polycyclic Aromatic Hydrocarbons, PAH, and Polychlorinated Biphenyls, PCB) in a sand-plant system has been carried out, with the reclamation of wastewater treatment plant biosolids for agriculture in mind. Carrot plants (Daucus carota) were grown on soilless culture (sand), to provide optimal transfer conditions, in plant containers inside a temperature regulated greenhouse. There were two types of experiment. The trace organic compounds have initially been introduced as pure substances. A second experiment has been carried out under the same conditions, but using biosolids. Plant development has been unaffected by the presence of the pure substances and the biosolids. The transfer of the trace organic compounds has been followed in the peel, the core and the leaves of the carrot plants. Results obtained are expressed as fluxes of the trace organic compounds into the plant. The results clearly show that trace organic compounds accumulate in the carrot peel