Wastewater Treatment Biosolids Research Articles

Pyrolysis Processing of PFAS-Impacted Biosolids, a Pilot Study

Concentrations of per- and poly-fluoroalkyl substances (PFAS) present in wastewater treatment biosolids is a growing concern. Pyrolysis is a thermal treatment technology for biosolids that can produce a useful biochar product with reduced levels of PFAS and other contaminants. In August 2020, a limited-scope study investigated target PFAS removal of a commercial pyrolysis system processing biosolids with analysis of 41 target PFAS compounds in biosolids and biochar performed by two independent laboratories. The concentrations of 21 detected target compounds in the input biosolids ranged between approximately 2 µg/kg and 85 µg/kg. No PFAS compounds were detected in the biochar. The PFAS concentrations in the biochar were assumed to equal the compounds’ minimum detection limits (MDLs). The pyrolysis system’s target PFAS removal efficiencies (REs) were estimated to range between >81.3% and >99.9% (mean = >97.4%) with the lowest REs being associated with the lowest detected PFAS concentrations and the highest MDLs. No information on non-target PFAS compounds in influent or effluent media or products of incomplete combustion were considered. Select gaseous emissions were measured by Fourier transform infrared spectroscopy and gas chromatography time-of-flight mass spectrometry to provide additional information on air emissions after process controls. This limited-scope study indicated that additional research to further understand this process is warranted. Implications Statement Development of alternative approaches to manage PFAS-impacted biosolids is of emerging international importance. A commercially operating biosolids pyrolysis process was shown to lower target PFAS levels in produced biochar. Additional research is warranted to understand all potential PFAS transformation emission routes and optimal air pollution emissions control strategies for this technology class.

Pyrolysis of Triclosan and Its Chlorinated Derivatives

Triclosan (TCS) is a commonly used antimicrobial agent which persists in the environment and may undergo chlorination and/or photodegradation to produce toxic polychlorinated dibenzo-p-dioxins and polychlorinated benzenes. TCS accumulates in wastewater treatment biosolids, which may be used to fuel waste-to-energy plants, although little is known about the fate of TCS at high temperatures. Here, we have studied the thermal decomposition of TCS and chlorinated TCS derivatives in the gas phase using computational chemistry coupled with reaction rate theory calculations to predict rate coefficients and develop a chemical kinetic model to simulate TCS pyrolysis in a plug flow reactor. TCS is shown to interconvert with 4-chloro-2-(2,4-dichlorophenoxy)phenol (TCSi) with a relatively low barrier, achieving equilibrium at temperatures of around 900 K and above. Dissociation of TCS and TCSi proceeds in parallel with barriers of ca. 60-65 kcal/mol to produce dichlorodibenzo-p-dioxin chlorobenzoquinone isomers. Reactor simulations demonstrate that TCS incineration at a temperature of 1100 K or higher leads to the formation of toxic chlorinated aromatics.

Soil microbiome response to land application of wastewater treatment biosolids

Soil microbiome response to land application of wastewater treatment biosolids

Synergism of co-digestion of food wastes with municipal wastewater treatment biosolids

Five semi-continuous flow anaerobic digesters treating a mixture of food waste (FW) and municipal biosolids (primary sludge and thickened wasted activated sludge) at an solids retention time (SRT) of 20 days and different blend ratios i.e. 0, 10%, 20%, 40% by volume with the fifth digester treating only biosolids at the same COD/N ratio as the 40% FW digester were operated to investigate co-digestion performance. Sixty days of steady-state operation at organic loading rates (OLR) of 2.2–3.85kgCOD/m3/d showed that COD removals were higher for the three co-digesters than for the two municipal biosolids digesters i.e. 61–69% versus 47–52%. Specific methane production per influent CODs were 1.3–1.8 folds higher in co-digestion than mono-digestion. The first-order COD degradation kinetic constants for co-digestion were more than double the mono-digestion. Additional methane production through synergism accounted for a minimum of 18–20% of the overall methane production. The estimated non-biodegradable fraction of the FW particulate COD was 7.3%. However, the co-digesters discharged 1.23–1.64 times higher soluble nitrogen than the control.

Development of a Metals Toxicity Protocol for Biosolids

Sixty percent of all wastewater treatment biosolids are recycled, compared to 30% in 1990. Environmental biosolids management systems are now commonly implemented for municipalities. The promotion of beneficial use of biosolids has transformed our historic view of processed wastewater treatment residuals. Instead of wastes requiring disposal, we now view biosolids as valuable manufactured products. Land application of biosolids has proven to be beneficial because organic matter and nutrients can be used effectively for enhancement of agricultural crop production. There is concern, however, about the potential for degradation of soil quality. Although thorough investigations of potential risk from biosolids have generally indicated that land application does not threaten human or ecosystem health, questions continue to arise concerning the safety of biosolids recycling. This project was initiated to evaluate the toxicity resulting from the amendment of soils with biosolids from municipal wastewater treatment. Toxicity was evaluated using standard tests including earthworm mortality, growth, and reproduction; seedling germination and root elongation; microbial respiration; and nematode mortality/reproduction. In addition, chemical lability tests for metals were employed including water soluble, exchangeable, and metals extractable by the physiologically based extraction test (PBET). This title belongs to WERF Research Report Series ISBN: 9781843396895 (eBook)

Speciation Matters: Bioavailability of Silver and Silver Sulfide Nanoparticles to Alfalfa (Medicago sativa).

Terrestrial crops are directly exposed to silver nanoparticles (Ag-NPs) and their environmentally transformed analog silver sulfide nanoparticles (Ag2S-NPs) when wastewater treatment biosolids are applied as fertilizer to agricultural soils. This leads to a need to understand their bioavailability to plants. In the present study, the mechanisms of uptake and distribution of silver in alfalfa (Medicago sativa) were quantified and visualized upon hydroponic exposure to Ag-NPs, Ag2S-NPs, and AgNO3 at 3 mg total Ag/L. Total silver uptake was measured in dried roots and shoots, and the spatial distribution of elements was investigated using transmission electron microscopy (TEM) and synchrotron-based X-ray imaging techniques. Despite large differences in release of Ag(+) ions from the particles, Ag-NPs, Ag2S-NPs, and Ag(+) became associated with plant roots to a similar degree, and exhibited similarly limited (<1%) amounts of translocation of silver into the shoot system. X-ray fluorescence (XRF) mapping revealed differences in the distribution of Ag into roots for each treatment. Silver nanoparticles mainly accumulated in the (columella) border cells and elongation zone, whereas Ag(+) accumulated more uniformly throughout the root. In contrast, Ag2S-NPs remained largely adhered to the root exterior, and the presence of cytoplasmic nano-SixOy aggregates was observed. Exclusively in roots exposed to particulate silver, NPs smaller than the originally dosed NPs were identified by TEM in the cell walls. The apparent accumulation of Ag in the root apoplast determined by XRF, and the presence of small NPs in root cell walls suggests uptake of partially dissolved NPs and translocation along the apoplast.

Performance of an anaerobic fluidized bed bioreactor (AnFBR) for digestion of primary municipal wastewater treatment biosolids and bioethanol thin stillage

The primary objective of this work was to investigate and compare the treatability of very high suspended solids with different biodegradable particulate fractions and COD fractionation, thin stillage (a by-product from the corn ethanol industry) as well as primary sludge from municipal wastewater treatment, using an anaerobic fluidized bed bioreactor (AnFBR) employing US Mesh 30 × 40 zeolite with a diameter of (dm) in the range of 425–610 μm and specific surface area (SSA) of 26.5 m2/g as the carrier media. Each experimental run lasted over a six-month period. Due to the long-term impact of accumulation of inert suspended solids in the AnFBR and potential active biomass washout leading to failure, treatability of high suspended-solid streams can be very challenging. Despite the very high strength of thin stillage and primary sludge with chemical oxygen demand of 130,000 mg TCOD/L and 42,000 mg TCOD/L respectively and suspended solids of 47,000 mg TSS/L and 34,000 mg TSS/L, the AnFBR showed, up to 88% and 82% TCOD and 78% and 82% TSS removal efficiencies from thin stillage and primary sludge respectively at very high organic and solids loading rates (OLR and SLR) of 29 kg COD/m3 d and 9.5 kg COD/m3 d and 10.5 kg TSS/m3 d and 10.3 kg TSS/m3 d respectively at hydraulic retention time (HRT) of 3.5 and 4 days. Maximum methane production yields of up to 0.31LCH4/gCOD and 0.25LCH4/gCOD were achieved for thin stillage and primary sludge respectively corresponding to biogas production rate per reactor volume of 15.8 Lgas/Lreactor d and 1.22LCH4/Lreactord.

Phosphorus Runoff from Waste Water Treatment Biosolids and Poultry Litter Applied to Agricultural Soils

Differences in the properties of organic phosphorus (P) sources, particularly those that undergo treatment to reduce soluble P, can affect soil P solubility and P transport in surface runoff. This 2-yr field study investigated soil P solubility and runoff P losses from two agricultural soils in the Mid-Atlantic region after land application of biosolids derived from different waste water treatment processes and poultry litter. Phosphorus speciation in the biosolids and poultry litter differed due to treatment processes and significantly altered soil P solubility and dissolved reactive P (DRP) and bioavailable P (FeO-P) concentrations in surface runoff. Runoff total P (TP) concentrations were closely related to sediment transport. Initial runoff DRP and FeO-P concentrations varied among the different biosolids and poultry litter applied. Over time, as sediment transport declined and DRP concentrations became an increasingly important component of runoff FeO-P and TP, total runoff P was more strongly influenced by the type of biosolids applied. Throughout the study, application of lime-stabilized biosolids and poultry litter increased concentrations of soil-soluble P, readily desorbable P, and soil P saturation, resulting in increased DRP and FeO-P concentrations in runoff. Land application of biosolids generated from waste water treatment processes that used amendments to reduce P solubility (e.g., FeCl(3)) did not increase soil P saturation and reduced the potential for DRP and FeO-P transport in surface runoff. These results illustrate the importance of waste water treatment plant process and determination of specific P source coefficients to account for differential P availability among organic P sources.

Effect of biosolids on refuse decomposition and phosphorus cycling

Laboratory-scale reactors containing mixtures of municipal solid waste and wastewater treatment biosolids were monitored to assess the effect of biosolids on refuse decomposition and on phosphorus (P) cycling and speciation among orthophosphate, acid-hydrolysable P, and organic P. The co-disposal of 10 to 20% (by wet weight) aerobically-digested biosolids with residential refuse was compatible with refuse decomposition although the biosolids did not increase either the maximum methane production rate or the cumulative yield, and did not reduce lag times to the onset of methane production. The results of this study indicated that dissolved reactive phosphorus (DRP) was the dominant dissolved P fraction throughout refuse decomposition and that it was negatively correlated with the methane production rate and pH (r² = 0.35 for both). P was not found to limit methane production. Biosolids increased dissolved P as well as ammonia-N in some reactors, but this did not have a significant impact on maximum methane production rates. The maximum tolerated Na+ and K+ concentrations during active methane production were at least 4100 mg Na+ L⁻¹ and 800 mg K+ L⁻¹, respectively.

EOLIA-SLUDGE: a Novel ‘Triple Bottom Line’ decision supporting tool for the sustainable management of wastewater treatment Biosolids

EOLIA-SLUDGE: a Novel ‘Triple Bottom Line’ decision supporting tool for the sustainable management of wastewater treatment Biosolids

Uptake of nonylphenol and nonylphenol ethoxylates by crested wheatgrass

Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids often are land applied, but little is known regarding the potential uptake of biosolid-derived contaminants by plants. Hydroponic experiments, 11 to 14 weeks in duration, were conducted to examine the uptake and translocation of 14C and unlabeled NP, nonylphenol tetraethoxylate (NPE4), and nonylphenol nonylethoxylate (NPE9) by crested wheatgrass (Agropyron cristatum). Phenol also was evaluated for comparison. Plant tissue was analyzed for 14C and for the parent compounds. Volatilization from the hydroponic system and rhizosphere mineralization also were quantified. At the conclusion of the study, most of the plant-associated 14C was found in the roots (NP = 98%, NPE4 = 92%, and NPE9 = 81%). Concentrations of 14C in the foliar tissue ranged from 0.002 to 0.045 mg-equivalent per kg (dry wt), but no parent compounds were detected, implying that the 14C was unextractable or in the form of metabolites. Transpiration stream concentration factors for NP, NPE4, and NPE9, calculated assuming the 14C was parent compound, were 0.012, 0.032, and 0.066, respectively. Little mineralization was observed for NP, NPE4, and NPE9 in the hydroponic system; however, for phenol, 16 to 30% of the added 14C was mineralized.

Nitric Oxide Emissions from the Soil to Lower Levels of the Troposphere

Emissions of nitric oxide from the soil to the lower troposphere under varying environmental conditions are considered. NO is a precursor in the formation of tropospheric ozone which can directly impact public health and the environment. Understanding and controlling of NO flux from soils to the troposphere can thus be advantageous, protecting air quality as well as conserving valued nitrogen fertilizers in agricultural settings. Comprehensive laboratory protocols have been developed, conducted, and published that consider the influence of mineral fertilizer, municipal wastewater, municipal wastewater treatment biosolids, swine waste, and toluene on NO emissions with varying soil temperature, moisture content, and pH. Laboratory results indicate that NO emissions from wastewater-amended soil have the highest mean emission rate (63 ng-N/m2s) followed by toluene-amended soil (47 ng-N/m2s), biosolid-amended soil (46 ng-N/m2s), mineral fertilizer-amended soil (44 ng-N/m2s), and then swine waste-amended soil (...

A Comparison of Fluid Bed and Multiple Hearth Biosolids Incineration

Incineration has been used as a disposal method for wastewater treatment biosolids for over sixty years. The first multiple hearth furnace for biosolids incineration was built in 1935 in Dearborn, MI. From that time through the late sixties, the multiple hearth was the thermal technique of choice for biosolids disposal. Today there are still some 150-175 aging multiple hearths in operation in North America. In the seventies, the fluid bed furnace became the preferred thermal technique for biosolids disposal, primarily due to tighter emission regulation and to increasing cost of auxiliary fuel. The first municipal fluid bed was installed in the USA at the Lynnwood, WA wastewater treatment plant in 1962. There have been over 125 fluid bed incinerators installed since then in North America.

Destruction of Wastewater Treatment Biosolids in Supercritical Water.

The destruction of biosolids generated from biological wastewater treatment was assessed under subcritical and supercritical water oxidation (SCWO) temperatures, A non-specific measure of the organic content of the waste, the chemical oxygen demand (COD), was used to indicate the progress of reaction. SCWO was capable of removing >99. 9% of the COD. The biosolids' organic content was classified into two components: easy-to-oxidize; and difficultto-oxidize. The removal of the difficult-to-oxidize component was adequately described by first order reactions with constants in the range of 0. 6×10-4-33. 4×10-4 (sec-1) within 300-400°C. Biosolids hydrolysis followed by oxidation was a major reaction mechanism resulting in the formation of volatile fatty acids.