Drinking Water Treatment Residuals Research Articles

Peroxymonosulfate activation by hydroxylamine-drinking water treatment residuals for the degradation of atrazine

Drinking water treatment residuals (WTRs) have been applied in organic pollutants degradation in water by generating reactive oxygen species from peroxymonosulfate (PMS), however, the slow transformation of Fe(III) to Fe(II) may limit its widespread application. Hydroxylamine (HA) was introduced into the system to enhance the degradation efficiency of atrazine (ATZ) and several key reaction parameters (HA concentration, PMS concentration, pH and temperature) were concerned to study their influence on ATZ degradation. The results revealed that ATZ degradation efficiency was enhanced in the HA/WTRs/PMS system. Effects of some basic inorganic ions (Cl−, SO42− and NO3−) and natural organic matter on ATZ degradation were investigated and results showed that both have an inhibitory effect on ATZ removal. In addition to the reduction role, HA can also react directly with PMS to produce free radicals that helpful for ATZ degradation. Sulfate radical and hydroxyl radicals were generated and sulfate radical was identified as primary radicals in the HA/WTRs/PMS system by alcohol quenching experiments. Moreover, the HA/WTRs/PMS system also showed good performance for ATZ degradation in authentic water like surface water and groundwater. Introduction of hydroxylamine into the system may promote organic pollutant degradation and use of WTRs as an iron source for PMS activation provides new ideas for sludge treatment.

Cobalt ferrite nanoparticles supported on drinking water treatment residuals: An efficient magnetic heterogeneous catalyst to activate peroxymonosulfate for the degradation of atrazine

Drinking water treatment residuals (WTRs), an iron-rich byproduct generated during potable water production, is a potential resource with utilizable value. In this study, with WTRs as potential iron source and catalyst support, a novel CoFe2O4@WTRs hybrid was fabricated via a modified chemical co-precipitation combined with calcination method and employed as high-efficient peroxymonosulfate (PMS) activator for the degradation of atrazine (ATZ). CoFe2O4 was successfully synthesized and well dispersed onto WTRs. CoFe2O4@WTRs exhibited superior catalytic reactivity towards PMS and 98.2% of ATZ degradation was achieved with 0.03 g L2−1 CoFe2O4@WTRs, 0.20 mM PMS, and 10 μM ATZ at initial pH 4.01. The catalytic performance of CoFe2O4@WTRs was evaluated with respect to various stoichiometric Co/Fe ratio, catalyst dosage, PMS concentration, and initial pH. Sulfate radical (SO4−), generated through cobalt-mediated heterogeneous and homogeneous activation reactions, dominated ATZ degradation in the CoFe2O4@WTRs/PMS system. The underlying activation mechanism was elaborated based on radical species determination and X-ray photoelectron spectroscopy (XPS) observations. The intermediates of ATZ were identified by LC-MS with three main degradation pathways proposed, including dealkylation, dechlorination-hydroxylation, and deamination-hydroxylation. Finally, CoFe2O4@WTRs showed good application prospect in the remediation of ATZ contaminated real water under acidic condition.

A simple method to improve the adsorption properties of drinking water treatment residue by lanthanum modification

The loading of La can substantially enhance the adsorption capability of drinking water treatment residue (DWTR) for better recycling. Normally, the modification was based on incubation of DWTR and La solution at a certain ratio, following by solid-liquid separation and drying processes. This study attempted to simplify La loading procedures by adopting high ratio of DWTR and La solution to eliminate the solid-liquid separation, aiming to promote the potential actual production. According to the results of the short- (2 d) and long-term (30 d) P adsorption tests, the N2 gas sorption and desorption analysis, the X-ray photoelectron spectroscopy analysis, and the metal fractionation, the substantial enhanced adsorption capability of the modified DWTR was maintained and the La loading mechanisms to DWTR changed little after eliminating solid-liquid separation processes during modification; typically, La loading increased the initial P adsorption rates from 1.00 (raw DWTR) to 6.08 and 6.03 mg g-1 d-1 for the modified DWTR with and without the separation processes. Furthermore, the DWTR before and after modification had little unfavorable effect on the survival of snail Bellamya aeruginosa, while eliminating the separation processes tended to reduce the bioavailability of Al, Fe, and La in the modified DWTR. These results demonstrated that solid-liquid separation was not the key step for DWTR modification and that the developed simple modification method was feasible for La loading to DWTR, promoting the beneficial recycling in environmental remediation.

Characteristics and mechanisms of molybdenum(VI) adsorption by drinking water treatment residue

Characteristics and mechanisms of molybdenum(VI) adsorption by drinking water treatment residue

Activation of peroxymonosulfate by magnetic catalysts derived from drinking water treatment residuals for the degradation of atrazine.

Magnetic catalysts (MCs) derived from iron-rich drinking water treatment residuals (WTRs) were prepared through pyrolysis treatment and introduced as activators of peroxymonosulfate (PMS) for refractory atrazine (ATZ) degradation. Comprehensive characterization analysis indicated that pyrolytic temperature could manipulate the crystalline structure evolution of the MCs and influence their physicochemical and catalytic properties. The catalytic performances of the as-prepared samples pyrolyzed at 600 °C (MC-600) and 1000 °C (MC-1000) were evaluated, and MC-1000 exhibited far more excellent catalytic reactivity than MC-600 in PMS oxidation system. Such difference was mainly attributed to that Fe3O4 and Fe° are the dominant active ingredients of MC-600 and MC-1000, respectively. The electron spin resonance (ESR) tests and radical quenching experiments revealed that hydroxyl radical (•OH) and sulfate radical (SO4•-) predominated in the MC-600/PMS and MC-1000/PMS systems, respectively. The mechanisms of the MCs-mediated PMS activation process were elucidated, among which the role of iron mineral phase was emphatically explored. Furtherly, possible degradation by-products were identified by LC-MS, and potential degradation pathways were proposed. Ultimately, the effects of pivotal parameters (i.e. MC-1000 dosage, PMS concentration, initial pH, and water matrix species) on ATZ degradation were investigated to assess the applicability of the MC-1000/PMS system.

Assessment of water treatment residuals as sorbent material in permeable reactive barriers: Application to a copper‐contaminated site

AbstractThe objective of this study is to design a pilot‐scale permeable reactive barrier (PRB) for the removal of copper from groundwater in Keweenaw Peninsula, Michigan. The reactive material selected for the barrier is drinking water treatment residuals (WTR)—the residuals of alum coagulants used in a local drinking water treatment plant. Physical and chemical properties of the WTR were determined. Synthetic precipitation leaching procedure tests indicated the concentrations of hazardous elements leached from the residuals do not exceed U.S. Environmental Protection Agency limits and, hence, can be safely recycled as PRB material. Batch reactor tests showed that equilibrium sorption of copper is high and fits a Langmuir‐type isotherm. Site characterization studies included groundwater flow direction, pore water velocity, and contaminant concentration to determine optimal dimensions and placement of the PRB. Permeameter tests were performed with various mixtures of the WTR and an inert support material (pea gravel) to determine the ideal mix to match the hydraulic conductivity of the field site. Kinetic and column experiments were conducted to understand the significance of chemical and physical mass transfer limitations. Based on the results, dimensions of a PRB to meet the Michigan Department of Environmental Quality target level of 0.031 milligrams per liter (mg/L) total Cu were calculated.

Adsorption of phosphorus with calcium alginate beads containing drinking water treatment residual.

Aluminum-based drinking water treatment residuals (DWTR) were encapsulated by alginate to develop a pelletized media (DWTR-CA beads) for phosphorus (P) adsorption. The beads were successfully manufactured to uniform size and shape requirements. The effects of DWTR powder concentration and particle size, and bead mean size on P adsorption, were investigated. The DWTR was found to be an important component in the beads for P adsorption, while the calcium alginate shell contributed little for P adsorption. The maximum P adsorption capacity of the DWTR-CA bead was 19.42 mg P/g wet beads, corresponding to a bead diameter of 3.1 ± 0.2 mm and DWTR concentration of 2% (1% weight/volume (W/V)), mg/mL). The adsorption data fit well with the intra-particle diffusion model and the pseudo-second-order kinetic model, while both the Langmuir and Freundlich adsorption isotherms described the adsorption process well. Furthermore, the study on the effect of pH on P adsorption showed that acidic conditions resulted in a better P adsorption and the DWTR-CA beads have the function of pH neutralization. The findings of this study show that the DWTR-CA beads are a promising adsorbent/substrate for P removal.

Removal of Acidity and Metals from Acid Mine Drainage-Impacted Water using Industrial Byproducts

One of the biggest environmental impacts of mining is the generation of acid mine drainage (AMD). In the absence of proper post-mining management practices, AMD pollution can cause massive environmental damage. Current AMD management practices often fail to meet the expectations of cost, efficiency, and sustainability. The objective of this study was to utilize the metal-binding and acid-neutralizing capacity of an industrial by-product that is otherwise landfilled, namely drinking-water treatment residuals (WTRs), to treat AMD-water, thus offering a green remediation alternative. AMD-water was collected from Tab-Simco coal mine in Carbondale, Illinois. It was highly acidic (pH 2.27), and contaminated with metals, metalloids and sulfate at very high concentrations. A filter media, prepared using locally-generated aluminum (Al) and calcium (Ca)-based WTRs, was used to increase pH and to remove metals and [Formula: see text] from AMD-water. Laboratory-batch sorption studies at various WTRs (Al and Ca):AMD-water ratios were performed to optimize the filter media. WTRs:sand ratio of 1:6 provided optimal permeability, and 1:1 Al-WTRs:Ca-WTRs ratio was the optimal sorbent mix for removal of the metals of concern. A scaled-up study using a 55-gallon WTRs and sand-based filter was designed and tested. The results showed that the filter media removed more than 99% of the initial Fe (137 mg/L), Al (80 mg/L), Zn (11 mg/L), Pb (7 mg/L), As (4 mg/L), Mn (33 mg/L), and 44% of the initial [Formula: see text] (2481 mg/L) from Tab-Simco AMD-water. pH increased from 2.27 to 7.8. Desorption experiments showed that the metals were irreversibly bound to the WTRs and were not released back to the water.

Water treatment residuals as soil amendments: Examining element extractability, soil porewater concentrations and effects on earthworm behaviour and survival

Drinking water treatment residuals (WTRs), the by-product of water clarification processes, are routinely disposed of via landfill however there is a growing body of research that demonstrates the material has great potential for beneficial use in environmental applications. Application to agricultural land is one option showing great promise (i.e. a low cost disposal route that provides organic matter input to soils and other potential benefits), however questions remain as to the impact such applications may have on earthworm survival and behaviour and also on the potential effects it may have on soil porewater chemistry. This study examined the leachability of elements within two types of WTRs (one Al- and one Fe- based) from England via 0.001 M CaCl2 solution, at varying pH, and via the Community Bureau of Reference (BCR) sequential extraction scheme. Earthworm avoidance, survival, growth, reproduction and element concentrations were examined in WTR-amended sandy soils (0%, 5%, 10%, 20% w/w), while soil porewaters were also recovered from experimental units and examined for element concentrations. The results revealed leachable element concentrations to be very low in both types of WTRs tested and so element leaching from these WTRs would be unlikely to pose any threat to ecosystems under typical agricultural soil conditions. However, when the pH was lowered to 4.4 there was a substantial release of Al from the Al-WTRs (382 mg/kg). Soil porewater element concentrations were influenced to some degree by WTR addition, warranting further examination in terms of any potential implications for nutrient supply or limitation. Earthworm avoidance of WTR-amended soil was only observed for Al-WTRs and only at the maximum applied rate (20% w/w), while survival of earthworms was not affected by either WTR type at any application rate. Earthworm growth and reproduction (cocoon production) were not affected at a statistically significant level but this needs further examination over a longer period of exposure. Increased assimilation of Al and Fe into earthworm tissues was observed at some WTR application rates (maximum fresh weight concentrations of 42 mg/kg for Al and 167 mg/kg for Fe), but these were not at levels likely to pose environmental concerns.

Activation of persulfate by modified drinking water treatment residuals for sulfamethoxazole degradation

In this work, drinking water treatment residuals (WTRs), an iron-rich safety byproducts, was modified via facile reduction calcination and subsequently proved as an effective persulfate (PS) activator for degradation of sulfamethoxazole (SMX). Various parameters affecting SMX degradation efficiency were tested, and the results showed that 80% of SMX (50 μM) was removed within 60 min in the presence of 2.0 mM PS and 0.2 g L−1 modified WTRs at pH 5.3 under ambient temperature. Radical scavenging and electron spin-resonance spectroscopy tests indicated that sulfate radical was a much more powerful active oxygen specie than hydroxyl radical for the SMX degradation in the WTRs/PS system. To understand the proposed activation mechanism, X-ray diffraction and X-ray photoelectron spectroscopy were applied to reveal the change of modified WTRs before and after use. This process confirmed that the activation mechanism was in situ homogenous and heterogeneous reaction simultaneously. Furthermore, liquid chromatography coupled with ion trap time-of-flight mass spectrometry was applied to identify the intermediates of SMX to understand the possible pathway. This work provides a novel value-added reuse approach for WTRs as an efficient and cost-effective heterogeneous activator for PS.

Chemical and ecotoxicological effects of the use of drinking-water treatment residuals for the remediation of soils degraded by mining activities

The aim of this study was to evaluate the use of drinking-water treatment residuals (DWTR) in the amendment of a soil affected by mining activities (Aljustrel mine, Portuguese sector of the Iberian Pyrite Belt), considering the effects on its chemical, biochemical and ecotoxicological characteristics. The DWTR had neutral characteristics (pH 6.7) and an organic matter (OM) content of 575 g kg−1 dry matter (DM), which makes them a potential amendment for the remediation of mine degraded soils, as they may correct soil acidity and reduce the extractable metal fraction. An incubation assay, with soil and DWTR, with or without lime, was carried out to test the doses to be used in the assisted-phytostabilization experiment. Based on the results obtained, the doses of DWTR used were the equivalent to 48, 96, and 144 t DM ha−1, with and without lime application (CaCO3 11 t DM ha−1). Agrostis tenuis Sibth was used as the test plant. Some amendments doses were able to improve soil characteristics (pH and OM content), to decrease metal extractability by 0.01 M CaCl2 (especially for Cu and Zn), and to allow plant growth, that did not occur in the non-amended soil. Copper, Pb and Zn concentrations in the plant material were lower than the maximum tolerable level for cattle feed, used as an indicator of risk of entry of those metals into the human food chain. The simultaneous application of DWTR (96 and 144 t ha−1), with lime, allowed a reduction in the mine soil ecotoxicity, as evaluated by some lethal and sub-lethal bioassays, including luminescence inhibition of Vibrio fischeri, Daphnia magna acute immobilization test, mortality of Thamnocephalus platyurus, and 72-h growth inhibition of the green microalgae Pseudokirchneriella subcapitata. However, DWTR were unable to increase soil microbial activity, evaluated by dehydrogenase activity, an important soil-health indicator. Also, OM content and NKjeldahl, concentrations increased slightly but remained low or very low (P and K extractable concentrations were not affected). In general, the bioassays highlighted a decrease in soil ecotoxicity with the presence of lime and DWTR (144 t DM ha−1). In conclusion, DWTR are recommended to amend acidic soils, with high concentrations of trace elements, but an additional application of organic or mineral fertilizers should be considered.

Recycling of drinking water treatment residue as an additional medium in columns for effective P removal from eutrophic surface water

This study assesses the feasibility of recycling drinking water treatment residue (DWTR) to treat eutrophic surface water in a one-year continuous flow column test. Heat-treated DWTR was used as an additional medium (2%–4%) in columns in case excessive organic matter and N were released from the DWTR to surface water. The results indicated that with minimal undesirable effects on other water properties, DWTR addition substantially enhanced P removal, rendering P concentrations in treated water oligotrophic and treated water unsuitable for Microcystis aeruginosa breeding. Long-term stable P removal by DWTR–column treatment was mainly attributed to the relatively low P levels in raw water (<0.108 mg L−1) and high P adsorption capability of DWTR, as confirmed by increases in amorphous Al/Fe in DWTR after the tests and low adsorption of P in the mobile forms. The major components of DWTR showed minimal changes, and potential metal pollution from DWTR was not a factor to consider during recycling. DWTR also enriched functional bacterial genera that benefitted biogeochemical cycles and multiple pollution control (e.g., Dechloromonas, Geobacter, Leucobacter, Nitrospira, Rhodoplanes, and Sulfuritalea); an apparent decrease in Mycobacterium with potential pathogenicity was observed in DWTR–columns. Regardless, limited denitrification of DWTR–columns was observed as a result of low bioavailability of C in surface water. This finding indicates that DWTR can be used with other methods to ensure denitrification for enhanced treatment effects. Overall, the use of DWTR as an additional medium in column systems can potentially treat eutrophic surface water.

Lanthanum-modified drinking water treatment residue for initial rapid and long-term equilibrium phosphorus immobilization to control eutrophication

This study presents an approach for developing inactivating materials to achieve an initial rapid and a long-term equilibrium P immobilization to control eutrophication based on drinking water treatment residue (DWTR), which is a byproduct of potable water production. By taking advantage of the long-term equilibrium P adsorption by DWTR, the La chemical properties, and the previous success of using La-modified bentonite clay (Phoslock®), we used DWTR as a La carrier with different ratios to develop the specific materials. The La loading mechanisms, the potentially toxic effect of La-modified DWTR on snail Bellamya aeruginosa (within 120 d), and the short- and long-term (within 80 d) P immobilization characteristics of the modified DWTR were investigated to understand the performance of the developed materials. The results showed that La loading into DWTR was based on ligand exchanges and the formation of new particles; DWTR loaded with <5% La had no toxicity against the snail. Most importantly, the loading of 5% La to DWTR substantially enhanced the rapid immobilization capacity of DWTR, achieving an initial rapid and a long-term equilibrium P adsorption in aqueous solutions. This study promotes the beneficial recycling of DWTR and results in a win-win situation for lake restoration.

Granulation of drinking water treatment residuals as applicable media for phosphorus removal

Recycling drinking water treatment residuals (DWTR) show promise as a strategy for phosphorus (P) removal; however, powdered DWTR is not an ideal practical medium due to clogging. This study granulates DWTR by entrapping powdered DWTR in alginate beads. Results show that granular DWTR has an appreciable amount of mesopores along with a Brunauer-Emmett-Teller (BET) surface area of 43.8 m2/g and total pore volume of 0.049 cm3/g. Most metals (e.g., Al, Ba, Be, Cd, Co, Cr, Mn, Ni, Pb, and Zn) in granular DWTR became more stable and granular DWTR could be considered non-hazardous material. Further analysis indicates that the granular DWTR has strong P adsorption capability with a maximum adsorption capacity of 19.70 mg/g as estimated by the Langmuir model. Good P adsorption may be attributed to the formation of Fe-PO4 and Al-PO4 associated with the amorphous state of enormous iron and aluminum in granular DWTR. More importantly, granular DWTR exhibits good mechanical stability and maintained its shape with weight loss below 12.49% after three recycling rounds. Overall, granular DWTR appears to serve as better media for phosphorus removal in water treatment structures such as wetlands.

Intermittent aeration incubation of drinking water treatment residuals for recycling in aquatic environment remediation

Abstract Recycling of drinking water treatment residuals (DWTRs) in aquatic environment remediation can provide numerous benefits. The hazardous effect of DWTR metals on the environment is shown to be limited; however, DWTR may release excessive nitrogen and organic matter, hindering recycling in the aquatic environment. To eliminate any potential unfavorable effect, self-purification via intermittent aeration incubation for DWTRs was developed. Results indicated that after approximately 5–6 months of incubation, the easily released nitrogen and organic matter in the DWTRs were mostly removed. The removed nitrogen was found to mainly consist of ammonium nitrogen from inorganic and organic nitrogen groups in the DWTRs. The removed organic matter consisted mainly of humic-like substances associated with the carboxyl group, distributed on the surface of the DWTRs. Biological mechanisms for effective nitrogen and organic matter removal were further explored based on the analysis of bacterial community structure, which indicated that the dominant bacteria genera (e.g., Geothrix, Methylotenera, and Geobacter) in the DWTRs after incubation were closely related to nitrogen and carbon cycles. In addition, the phosphorus adsorption of the DWTRs after incubation was maintained, and the specific surface area, total pore volume, microporosity, and mesoporosity of the DWTRs after incubation tended to increase because of organic matter removal. Accordingly, intermittent aeration not only addressed the concerns caused by potential excessive release of nutrients from DWTRs but also enhanced the favorable effect of DWTRs on biogeochemical cycles. Self-purification can potentially promote the beneficial recycling of DWTRs in the aquatic environment.

Activation of peroxymonosulfate using drinking water treatment residuals for the degradation of atrazine

Drinking water treatment residuals (WTRs) are safe byproducts of water treatment plants containing iron. This work studies the degradation of atrazine (ATZ) by WTR-catalyzed peroxymonosulfate (PMS) in aqueous solutions. Factors that affect the catalytic performance (the PMS concentration, catalyst dose, initial solution pH, reaction temperature and water matrix species) were investigated. The results show that the catalytic degradation efficiency of ATZ increases with the increase in PMS concentration and temperature, whereas a higher content of WTRs results in lower removal efficiency because of the quenching effect and negative effect of high pH. For an initial solution pH of 3 and 5, 94.1% and 87.4% of ATZ degradation can be achieved within 6h, whereas the value is only 26% for pH of 7. The production of sulfate radicals (SO4−) and hydroxyl radicals (OH) was confirmed by classic radical quenching and electron spin resonance (ESR) tests. Based on the GC–MS and LC–MS results, the main degradation pathways of ATZ may contain dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation processes. In addition to the ATZ removal ability, the WTRs/PMS system can simultaneously remove phosphorus. This article provides a new idea for wastewater treatment and usage of WTRs as a resource.

The stability of drinking water treatment residue with ozone treatment

ABSTRACTThe best management of drinking water treatment residue (DWTR) in environmental remediation should be based on comprehensively understanding the effectiveness and risk of DWTR. In this study, the variation in physicochemical properties, metal lability, and adsorption capability of DWTR under oxidizing condition were investigated. The oxidizing condition was set up using ozone treatment, and the laboratory incubation test were performed within 50 d in association with thermogravimetry, Fourier Transform Infrared Spectrometry, specific surface area and porosity analyzer, fractionation, and P adsorption test. The results showed that ozone treatment had limited effect on the properties of organic matter, the lability of Al, Cu, and Fe, the P adsorption capability, and the distributions of the adsorbed P in DWTR, but the treatment increased N2 sorption/desorption, specific surface area, total pore volume of DWTR and led to the transformation of Mn from acid-soluble to reducible fractions. These findings demonstrated that DWTR generally kept stable under oxidizing environment; even oxidizing environment may induce a tendency of increasing the adsorption capability and decreasing the environmental risk of DWTR. Accordingly, the effectiveness and safety of DWTR can be maintained under natural aerobic environment, and DWTR is a reliable adsorbent that could be recycled in environmental remediation.

Drinking water treatment residual use in urban soils: Balancing metal immobilization and phosphorus availability

Pollution in urban environments has raised concerns about the consumer safety of food produced by urban horticulture. Could a solid by-product of drinking water treatment provide the answer? Soil amendment with drinking water treatment residuals (DWTRs) has been shown to limit the uptake of metal contaminants, effectively immobilizing these elements within the soil; however, DWTRs possess a strong specific affinity for P and soil amendment with DWTRs can reduce P availability, thereby inducing plant P deficiencies and restricting growth. We conducted a glasshouse pot experiment to investigate the effect of alum-based DWTR amendment rate and P fertilizer placement method on Brassica pekinensis growth and As, Cd and P uptake under controlled conditions. Amendment of sandy loam soil A with 2–4wt% DWTRs significantly (p<0.001) reduced the Cd content of B. pekinensis tissues relative to untreated controls, with no significant difference in the P content of B. pekinensis tissues. Across all DWTR application rates examined (2–6wt%), banded P fertilizer application resulted in 30–47% greater aboveground tissue P concentration compared to broadcast P fertilizer treatments (p<0.05). Both the As and Cd content of B. pekinensis tissues were significantly (p<0.001) reduced following 2–6wt% amendment of sandy loam B with DWTRs. Results showed that a DWTR amendment rate of 2wt% coupled with banded P fertilizer application resulted in the greatest B. pekinensis aboveground tissue biomass, along with a reduction in plant tissue Cd or As concentrations not significantly different from higher rates of DWTR amendment. Tissue P concentrations of B. pekinensis grown in soils amended with 2wt% DWTRs were adequate for uninhibited plant growth. The use of DWTRs as an amendment to urban horticultural soils may provide a low-cost means of immobilizing trace metals without limiting plant uptake of applied fertilizer P. Additional study is required to quantify trace element release from DWTR-amended soils as a function of soil oxidation-reduction status.

Trace elements bioavailability to Triticum aestivum and Dendrobaena veneta in a multielement-contaminated agricultural soil amended with drinking water treatment residues

The in situ stabilization of multielement-contaminated agricultural soils has limited effectiveness when using common single amendments. This study examined the use of drinking water treatment residues (WTR), based on (hydr)oxides of Fe, Al, or Mn, as a cost-effective solution to optimize the immobilization of metals (Cd, Pb, Zn) and As. Trace elements (TE) bioavailability was assessed under semi-controlled conditions in a pot study cultivating winter wheat (Triticum aestivum L. cv. Tiger) until maturity. An Fe-based WTR and a Mn-based WTR, applied at rates of 0.5 and 1% (m/m), were related to effects of lime marl (LM) application. Additionally, a bioassay with earthworms (Dendrobaena veneta) was conducted. Both bioassays were compared with measurements of NH4NO3-soluble, diffusive gradients in thin film (DGT)-available and soil solution TE concentrations, representing well-established surrogates for mimicking the bioavailable element fractions in soil. The application of the Fe-based WTR reduced As accumulation in vegetative wheat tissues (by up to 75%) and earthworms (by up to 41%), which corresponded with the findings from soil chemical analyses and improved plant growth and earthworm body weight. However, As concentrations in cereal grains were not affected, Cd or Pb accumulation by wheat was not mitigated, and Zn uptake was enhanced. By contrast, the Mn-based WTR effected the greatest reduction in Pb uptake, and lowered Cd transfer to wheat grain (by up to 25%). Neither the NH4NO3-soluble nor DGT-available concentrations matched with Cd and Zn accumulation in plants or earthworms, indicating interferences due to competition for binding sites according to the biotic ligand model. The results obtained in this study suggest that a bioassay with key species prior to field application should be mandatory when designing in situ stabilization options. The application of WTR to an agricultural soil strongly affected TE bioavailability to plants and earthworms. Low application rates tended to improve biomass production of biota. Higher application rates involved risks (e.g., P fixation, TE inputs), and none of the amendments tested could immobilize all targeted elements.

Thermal modification of aluminum drinking water treatment residuals for removal of Congo red from water

Thermal modification of aluminum drinking water treatment residuals for removal of Congo red from water