Innovative determination of the specific anammox activity for anammox sludge from continuous flow reactors: A comparison between continuous flow test and batch test

A novel method for measuring specific anammox activity (SAA) was proposed based on continuous flow tests to accurately determine the SAA of anammox sludge from continuous flow reactors, resolving the challenges of inaccurate SAA assessment caused by substrate shock to anammox bacteria. Results showed SAA of expanded granular sludge bed sludge via batch tests (0.101 ± 0.018 g-N·g-VSS-1·d-1) was lower than continuous flow tests (0.206 ± 0.010 g-N·g-VSS-1·d-1) (p < 0.05), highlighting the impact of substrate shock. Conversely, SAA of sequencing batch reactor sludge assessed via batch tests (0.878 ± 0.008 g-N·g-VSS-1·d-1) was higher than continuous flow tests (0.809 ± 0.005 g-N·g-VSS-1·d-1) (p < 0.01), attributed to endogenous denitrification. The advantages of continuous flow tests over batch tests included milder feeding way, stricter anaerobic conditions, and minimal sampling impact on system. Our study contributes to more accurate measurements of SAA of anammox sludge from continuous flow reactors, favoring long-term robust operation of anammox reactors.

Combining a Standardized Batch Test with the Biotic Ligand Model to Predict Copper and Zinc Ecotoxicity in Soils

Extraction of soil samples with dilute CaCl₂ solution in a routinely performed batch test has potential to be used in site-specific assessment of ecotoxicological risks at metal-contaminated sites. Soil extracts could potentially give a measure of the concentration of bioavailable metals in the soil solution, thereby including effects of soil properties and contaminant "aging." We explored the possibility of using a 0.001 M CaCl₂ batch test combined with biotic ligand models (BLMs) for assessment of ecotoxicity in soils. Concentrations of Cu²⁺ and Zn²⁺ in soil extracts were linked to responses in ecotoxicity tests (microbial processes, plants, and invertebrates) previously performed on metal-spiked soils. The batch test data for soils were obtained by spiking archived soil materials using the same protocol as in the original studies. Effective concentration values based on free metal concentrations in soil extracts were related to pH by linear regressions. Finally, field-contaminated soils were used to validate model performance. Our results indicate a strong pH-dependent toxicity of the free metal ions in the soil extracts, with R² values ranging from 0.54 to 0.93 (median 0.84), among tests and metals. Using pH-adjusted Cu²⁺ and Zn²⁺ concentrations in soil extracts, the toxic responses in spiked soils and field-contaminated soils were similar, indicating a potential for the calibrated models to assess toxic effects in field-contaminated soils, accounting for differences in soil properties and effects of contaminant "aging." Consequently, evaluation of a standardized 0.001 M CaCl₂ batch test with a simplified BLM can provide the basis for an easy-to-use tool for site-specific risk assessment of metal toxicity to soil organisms. Environ Toxicol Chem 2022;41:1540-1554. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Methane oxidation in a landfill biowindow under wide seasonally fluctuating climatic conditions

In the current study, a pilot biowindow was constructed in a closed cell of a Canadian Landfill, undergoing high seasonal fluctuations in the temperature from -30 in winter to 35 in summer. The biowindow was filled with biosolids compost amended with yard waste and leaf compost with the ratio of 4:1 as the substrate layer. Two years of monitoring of methane (CH₄) oxidation in the biowindow led to remarkable expected observations including a thick, solid winter frost cover affecting gas exchange in winter and temperatures above 45 ℃ in the biowindow in late summer. A high influx compared to the reported values was observed into the biowindow with an average value of 1137 g.m^-2.d^-1, consisting of 64% of CH₄ and 36% of carbon dioxide (CO₂) in the landfill gas. The variations in the temperature and moisture content (MC) of the compost layer in addition to the influx fluctuations affected CH₄ oxidation efficiency; however, a high average CH₄ oxidation rate of 237 g.m^-2.d^-1 was obtained, with CH₄ being mostly oxidized at top layers. The laboratory batch experiments verified that thermophilic methane-oxidizing bacteria (MOB) were active throughout the study period and oxidized CH₄ with a higher rate than mesophilic MOB. The methanotrophic potential of the compost mixture showed an average value of 282 µmol.g^-1.d^-1 in the entire period of the study which is in the range of the highest reported maximum CH₄ oxidation rates. The adopted compost mixture was suitable for CH₄ oxidation if the MC was above 30%. The significance of MC variations on CH₄ oxidation rate depended on the temperature range within the biowindow. At temperatures below 2 ℃, between 29 and 31℃, and above 45 ℃, MC was not a controlling factor for mesophilic CH₄ oxidation.

Phosphorus removal in denitrifying woodchip bioreactors varies by wood type and water chemistry

Denitrifying woodchip bioreactors are a practical nitrogen (N) mitigation technology but evaluating the potential for bioreactor phosphorus (P) removal is highly relevant given that (1) agricultural runoff often contains N and P, (2) very low P concentrations cause eutrophication, and (3) there are few options for removing dissolved P once it is in runoff. A series of batch tests evaluated P removal by woodchips that naturally contained a range of metals known to sorb P and then three design and environmental factors (water matrix, particle size, initial dissolved reactive phosphorus (DRP) concentration). Woodchips with the highest aluminum and iron content provided the most dissolved P removal (13±2.5 mg DRP removed/kg woodchip). However, poplar woodchips, which had low metals content, provided the second highest removal (12±0.4 mg/kg) when they were tested with P-dosed river water which had a relatively complex water matrix. Chemical P sorption due to woodchip elements may be possible, but it is likely one of a variety of P removal mechanisms in real-world bioreactor settings. Scaling the results indicated bioreactors could remove 0.40 to 13 g DRP/ha. Woodchip bioreactor dissolved P removal will likely be small in magnitude, but any such contribution is an added-value benefit of this denitrifying technology.

Determination of distribution coefficient of uranium from physical and chemical properties of soil

Uranium is a long lived radioactive element which is naturally present in minute concentrations in igneous, sedimentary and metamorphic rocks. These rocks when subjected to weathering results in the formation of soil which also has traces of uranium. Distribution coefficient (K_d) is a crucial parameter in environmental assessment which is used to predict the interaction and transport of uranium in groundwater. The objective of the study is to estimate the K_d of uranium in soils and to develop a relation between this and the soil parameters. Seven rock samples and twenty three soil samples were collected during this study. The K_d of rock samples of different grain sizes where determined and the soil samples were analysed for electrical conductivity, pH, grain size, bulk density, particle density, porosity, calcium carbonate, cation exchange capacity and K_d. The K_d of the soil increases with increase in soil pH up to 6, after which it gradually decreases. Multiple regression analysis was performed to quantify the effect of various soil parameters on soil K_d and equations were statistically significant. Thus, soil K_d in a region could be predicted using limited soil properties with such statistically significant equations.

Leaching behavior of pharmaceuticals and their metabolites in the soil environment

Pharmaceuticals constitute a significant group of emerging pollutants (EPs). The use of pharmaceuticals in animal breeding causes them to reach the soil environment in excrement and fertilizers. Depending on their chemical properties, pharmaceuticals can be sorbed to the soil or be washed out with rainfall and eventually be entered into groundwater. This paper evaluates the mobility of tramadol (TRA) and carbamazepine (CBZ), and two transformation products, O-desmethyltramadol (O-DMTRA) and 10,11-dihydro-10-hydroxycarbamazepine (10-OH-CBZ) in soils. Both pharmaceuticals are applied in human and animal treatment, which makes them enter the environment in native and metabolized form in high doses. Experiments were carried out in accordance with the OECD 106 procedure (batch tests) and DIN 19528:2009-01 procedure (percolation column test). The adsorption coefficients (K_d) for TRA, CBZ, O-DMTRA and 10-OH-CBZ were, respectively, 1.41 ± 0.10, 1.87 ± 0.06, 0.90 ± 0.03 and 0.37 ± 0.07 for sandy soil RS04, and 18.09 ± 0.78, 2.56 ± 0.05, 10.89 ± 0.17 and 0.56 ± 0.38  L kg^-1 for loamy soil RS06. The percolation column test was carried out for sandy soil RS04. The results obtained for TRA and O-DMTRA under static conditions indicated a high mobility of these compounds in soil, whereas the column leaching experiment showed that these compounds bind strongly to soil particles. A correlation between static and dynamic tests was observed in the case of CBZ and 10-OH-CBZ. These compounds will probably be characterized by a high or moderate mobility in soil.

Fate and transport of nanoplastics in complex natural aquifer media: Effect of particle size and surface functionalization

Environmental processes of nanoplastics in heterogeneous natural groundwater systems remain unclear. In this study, the control of particle size and surface functional groups on the fate and transport of nanoplastics in an organic matter (OM) rich aquifer was explored using batch and column tests. The carboxyl-modified 200 nm (200CNP), carboxyl-modified 50 nm (50CNP), and amino-modified 50 nm (50ANP) polystyrene latex beads were used as surrogates for nanoplastics of contrasting sizes and surface functional groups. Aquifer sand and natural groundwater sampled from an agriculture-impacted shallow sandy aquifer were processed to obtain granule beds with/out surface minerals and groundwater containing different-sized fractions of OM. Results show that particle size controlled the hetero-aggregation rate of nanoplastics with OM and Ca²⁺: a larger size resulting in a lower reaction rate led to a higher stability of 200CNP than 50CNP and 50ANP. Meanwhile, surface functional groups appeared to affect the affinity of OM and Ca²⁺ to nanoplastics, i.e. the amino group allowed the adsorption of dissolved OM on the particle but inhibited the adsorption of Ca²⁺ and suspended OM, while the carboxyl group allowed adsorption of the all. The resulting variable OM coatings formed on the different nanoplastics played a critical role in determining the particle stability and mobility, i.e. the suspended OM increased both the particle stability and mobility while the dissolved OM reduced both. These findings suggest that: 1. Depending on the OM properties, the influence of particle size and surface group on the nanoplastic processes might be secondary to the OM impact; 2. In evaluating the OM impact, not only the OM concentration but also the size and surface physiochemistry of the OM should be characterized. The insight gained is important to predict the concentration evolution pattern of weathered nanoplastics in OM-impacted sandy aquifers.

Biochemical methane potential (BMP) tests: Reducing test time by early parameter estimation

Biochemical methane potential (BMP) test is a key analytical technique to assess the implementation and optimisation of anaerobic biotechnologies. However, this technique is characterised by long testing times (from 20 to >100days), which is not suitable for waste utilities, consulting companies or plants operators whose decision-making processes cannot be held for such a long time. This study develops a statistically robust mathematical strategy using sensitivity functions for early prediction of BMP first-order model parameters, i.e. methane yield (B₀) and kinetic constant rate (k). The minimum testing time for early parameter estimation showed a potential correlation with the k value, where (i) slowly biodegradable substrates (k≤0.1d^-1) have a minimum testing times of ≥15days, (ii) moderately biodegradable substrates (0.1<k<0.2d^-1) have a minimum testing times between 8 and 15 days, and (iii) rapidly biodegradable substrates (k≥0.2d^-1) have testing times lower than 7days.

Analysis and interpretation of the leaching behaviour of waste thermal treatment bottom ash by batch and column tests

This paper investigates the leaching behaviour of specific types of waste thermal treatment bottom ash (BA) as a function of both pH and the liquid-to-solid ratio (L/S). Specifically, column percolation tests and different types of batch tests (including pH-dependence) were applied to BA produced by hospital waste incineration (HW-I), Refuse Derived Fuel (RDF) gasification (RDF-G) and RDF incineration (RDF-I). The results of these tests were interpreted applying an integrated graphical and modelling approach aimed at identifying the main mechanisms (solubility, availability or time-controlled dissolution and diffusion) governing the release of specific constituents from each type of BA. The final aim of this work was in fact to gain insight on the information that can be provided by the leaching tests applied, and hence on which ones may be more suitable to apply for assessing the leaching concentrations expected in the field. The results of the leaching tests showed that the three samples of analysed BA presented differences of orders of magnitude in their leaching behaviour, especially as a function of pH, but also in terms of the L/S. These were mainly related to the differences in mineralogy of the samples. In addition, for the same type of bottom ash, the comparison between the results of batch and percolation column tests, expressed in terms of cumulative release, showed that for some constituents (e.g. Mg for HW-I BA and Cu for RDF-G BA) differences of over one order of magnitude were obtained due to variations in pH and DOC release. Similarly, the eluate concentrations observed in the percolation tests, for most of the investigated elements, were not directly comparable with the results of the pH-dependence tests. In particular, in some cases the percolation test results showed eluate concentrations of some constituents (e.g. K and Ca in HW-I BA) of up to one order of magnitude higher than the values obtained from the pH-dependence experiments at the same pH value. This was attributed to a rapid washout from the column of the soluble phases present in the BA. In contrast, for other constituents (e.g. Mg and Ba for the RDF-G BA), especially at high L/S ratios, the concentrations in the column tests were of up to one order of magnitude lower than the solubility value, indicating release under non-equilibrium conditions. In these cases, batch pH-dependence tests should be preferred, since column tests results could underestimate the concentrations expected in the field.

Use of CAH-degrading bacteria as test-organisms for evaluating the impact of fine zerovalent iron particles on the anaerobic subsurface environment

The release of fine zerovalent iron (ZVI) particles in the environment after being introduced for in-situ treatment of compounds like chlorinated aliphatic hydrocarbons (CAHs) may raise questions toward environmental safety, especially for nanoscale materials. Classical single-species ecotoxicity tests do focus on aerobic conditions and are only relevant for the scenario when ZVI-particles reach surface water. Herein, we present an alternative approach where a CAH-degrading mixed bacterial culture was used as test-organisms relevant for the anaerobic subsurface. The impact of different ZVI particles on the bacterial culture was evaluated mainly by quantifying ATP, a reporter molecule giving a general indication of the microbial activity. These lab-scale batch tests were performed in liquid medium, without protecting and buffering aquifer material, as such representing worst-case scenario. The activity of the bacterial culture was negatively influenced by nanoscale zerovalent iron at doses as low as 0.05 g L(-1). On the other hand, concentrations up to 2 g L(-1) of several different types of microscale zerovalent iron (mZVI) particles stimulated the activity. However, very high doses of 15-30 g L(-1) of mZVI showed an inhibiting effect on the bacterial community. Negative effects of ZVIs were confirmed by H2 accumulation in the batch reactors and the absence of lactate consumption. Observed inhibition also corresponded to a pH increase above 7.5, explicable by ZVI corrosion that was found to be dose-dependent. The obtained results suggest that low doses of mZVIs will not show severe inhibition effects on the microbial community once used for in-situ treatment of CAHs.

Secondary formation of disinfection by-products by UV treatment of swimming pool water

Formation of disinfection by-products (DBPs) during experimental UV treatment of pool water has previously been reported with little concurrence between laboratory studies, field studies and research groups. In the current study, changes in concentration of seven out of eleven investigated volatile DBPs were observed in experiments using medium pressure UV treatment, with and without chlorine and after post-UV chlorination. Results showed that post-UV chlorine consumption increased, dose-dependently, with UV treatment dose. A clear absence of trihalomethane formation by UV and UV with chlorine was observed, while small yet statistically significant increases in dichloroacetonitrile and dichloropropanone concentrations were detected. Results indicate that post-UV chlorination clearly induced secondary formation of several DBPs. However, the formation of total trihalomethanes was no greater than what could be replicated by performing the DBP formation assay with higher chlorine concentrations to simulate extended chlorination. Post-UV chlorination of water from a swimming pool that continuously uses UV treatment to control combined chlorine could not induce secondary formation for most DBPs. Concurrence for induction of trihalomethanes was identified between post-UV chlorination treatments and simulated extended chlorination time treatment. Trihalomethanes could not be induced by UV treatment of water from a continuously UV treated pool. This indicates that literature reports of experimentally induced trihalomethane formation by UV may be a result of kinetic increase in formation by UV. However, this does not imply that higher trihalomethane concentrations would occur in pools that apply continuous UV treatment. The bromine fraction of halogens in formed trihalomethanes increased with UV dose. This indicates that UV removes bromine atoms from larger molecules that participate in trihalomethane production during post-UV chlorination. Additionally, no significant effect on DBP formation was observed due to photo-inducible radical forming molecules NO3- (potentially present in high concentrations in pool water) and H2O2 (added as part of commercially employed DBP reducing practices).

Correlation between biogas yield and chemical composition of energy crops

The scope of this study was to investigate the influence of the chemical composition of energy crops on biogas and methane yield. In total, 41 different plants were analyzed in batch test and their chemical composition was determined. For acid detergent lignin (ADL) content below 10% of total solids, a significant negative correlation for biogas and methane yields (r≈-0.90) was observed. Based on a simple regression analysis, more than 80% of the sample variation can be explained through ADL. Based on a principal component analysis and multiple regression analysis, ADL and hemicellulose are suggested as suitable model variables for biogas yield potential predictions across plant species.

Column and batch tests of sulfonamide leaching from different types of soil

Sulfonamides (SAs) and their metabolites present severe hazards to human health and the environment, mainly because of antibiotic resistance. Knowledge of their bioavailability, including their sorption to soils and their impact on the soil-groundwater pathway, is crucial to their risk assessment. Laboratory batch and column leaching tests are important tools for determining the release potential of contaminants from soil or waste materials. Batch and column tests were carried out with soils differing in particle size distribution, organic matter content and pH, each spiked with sulfonamides (sulfadimethoxine (SDM), sulfaguanidine (SGD), sulfisoxazole (SX)). In order to test the applicability of leaching tests to polar contaminants batch and column tests were also compared. In the column tests, release was found to depend on the properties of both soil and sulfonamides. The fastest release was observed for coarse-grained soil with the smallest organic matter content (MS soil; 100% decrease in concentration until liquid-to-solid ratio (L/S) of 0.9 L kg(-1) for all SAs). The slowest release was established for sulfadimethoxine (24.5% decrease in concentration until L/S 1.22 L kg(-1)). The results of the batch and column tests were comparable to a large extent, with slightly higher concentrations being obtained in the column test experiments of fine-grained soils with a high organic matter content.