Use of a Waste-Derived Linde Type-A Immobilized in Agarose for the Remediation of Water Impacted by Coal Acid Mine Drainage at Pilot Scale.

A new adsorbent based on an immobilized waste-derived LTA zeolite in agarose (AG) has proven to be an innovative and efficient alternative for removing metallic contaminants from water impacted by acid mine drainage (AMD) because the immobilization prevents the solubilization of the zeolite in acidic media and eases its separation from the adsorbed solution. A pilot device was developed containing slices of the sorbent material [AG (1.5%)-LTA (8%)] to be used in a treatment system under an upward continuous flow. High removals of Fe2+ (93.45%), Mn2+ (91.62%), and Al3+ (96.56%) were achieved, thus transforming river water heavily contaminated by metallic ions into water suitable for non-potable use for these parameters, according to Brazilian and/or FAO standards. Breakthrough curves were constructed and the corresponding maximum adsorption capacities (mg/g) (Fe2+, 17.42; Mn2+, 1.38; Al3+, 15.20) calculated from them. Thomas mathematical model was well fitted to the experimental data, indicating the participation of an ion-exchange mechanism in the removal of the metallic ions. The pilot-scale process studied, in addition to being highly efficient in removing metal ions at toxic levels in AMD-impacted water, is linked to the sustainability and circular economy concepts, due to the use as an adsorbent of a synthetic zeolite derived from a hazardous aluminum waste.

Highly efficient removal of aluminum, iron, and manganese ions using Linde type-A zeolite obtained from hazardous waste.

Coal acid mine drainage (AMD) contaminates natural water to form mine-impacted water (MIW), which is characterized by high levels of acidity, sulfate, and metallic ions. This study investigates the use of a Linde Type-A (LTA) zeolite obtained from a hazardous industrial waste for Al3+, Fe2+, and Mn2+ removal from synthetic aqueous solutions. The aim of this study is to stablish a basis for the subsequent treatment of MIW in order to obtain reuse water. In a central composite rotatable design (CCRD) study, 8.25 g L-1 zeolite and 147 rpm were the optimal conditions for treating the multicomponent solution, yielding 99.9, 99.9 and 99.3% removal for Al3+, Fe2+, and Mn2+, respectively. Isothermal studies showed that the affinity of the ions by the zeolite were ranked as Al3+>Mn2+>Fe2+. The best fitting isothermal models for monocomponent solutions were Tóth, Freundlich, and Sips for Al3+, Fe2+, and Mn2+, respectively. In the multicomponent solution, Sips and Freundlich were the better fitting models for Al3+ and Mn2+, respectively, indicating a weakness of the sorbate-sorbent interactions. Kinetic studies revealed that the quantitative removal of Al3+ was achieved in 5 min. The multicomponent solution was transformed into water that was suitable for non-potable use after an optimal time of 60 min. The results demonstrate that LTA zeolite synthetized from hazardous waste has a high potential for remediating contaminated water by metallic ions at low dosages and short times. Using LTA zeolite for remediating contaminated water could make a positive contribution to the circular economy and environmental sustainability.

Biostimulation of sulfate-reducing bacteria and metallic ions removal from coal mine-impacted water (MIW) using shrimp shell as treatment agent.

This paper comprises several assays aiming to identify the basis for the bioremediation of mine-impacted water (MIW). To do so, the conditions for build anoxic microcosms for treating this effluent were varied, containing MIW, and a source of chitin, to biostimulate sulfate-reducing bacteria (SRB). The chitin sources were: commercial chitin (CHIT) and shrimp shell (SS), which in addition to chitin, contains CaCO3, and proteins in its composition. The CHIT assays were not successful in sulfate-reduction, even when the pH was increased with CaCO3. However, in all SS assays the SRB development was successful (85% sulfate removal for assay 3), including the metal-free (MF-SS) assay (75% for assay 5). High-throughput sequencing analysis revealed the structure of bacterial community in the SS assay: the most abundant genera were Clostridium and Klebsiella, both fermentative and chitinase producers; a few SRB from the genera Desulfovibrio and Desulfosporosinus were also detected. In the MF-SS assay, Desulfovibrio genuswas detected but Comamonas was dominant. It could be deduced that SS is a suitable substrate for SRB development, but CHIT is not. The sulfate-reduction process was provided by the cooperation between fermentative/chitinase-producer bacteria together with SRB, which leads to efficient MIW treatment, removing sulfate and metallic ions.

Sulfate removal from mine-impacted water by electrocoagulation: statistical study, factorial design, and kinetics.

This work aimed to remove sulfate and acidity from mine-impacted water (MIW) via electrocoagulation (EC), a technique which stands as an advanced alternative to chemical coagulation in pollutant removal from wastewaters. The multiple electrochemical reactions occurring in the aluminum anode and the stainless steel cathode surfaces can form unstable flakes of metal hydroxysulfate complexes, causing coagulation, flocculation, and floatation; or, adsorption of sulfate on sorbents originated from the electrochemical process can occur, depending on pH value. Batch experiments in the continuous mode of exposition using different current densities (35, 50, and 65 A m-2) were tested, and a statistical difference between their sulfate removals was detected. Furthermore, the intermittent mode of exposure was also tested by performing a 22-factorial design to verify the combination with different current densities, concluding that better efficiencies of sulfate removal were obtained in the continuous mode of exposition, even with lower current densities. After 5 h of electrocoagulation, sulfate could be removed from MIW with a mean efficiency of 70.95% (in continuous mode of exposition and 65 A m-2 current density), and this sulfate removal follows probable third-order decay kinetics in accordance with the quick drop in sulfate concentration until 3 h of exposure time, remaining virtually constant at longer times. Graphical abstract.

Degradação sazonal de efluentes têxteis por processo foto-Fenton solar mediado por ferrioxalato: descoloração e comportamento dos sólidos / Seasonal degradation of textile effluents through the solar photo-Fenton process mediated by ferrioxalate: discoloration and behavior of solids

RESUMO Neste trabalho foi avaliado o processo foto-Fenton solar mediado por ferrioxalato como tratamento primário de um efluente têxtil bruto (E1) e como um processo de polimento, após processo de lodos ativados (E2). Por um ano, ao menos uma vez por mês, a eficiência de descoloração e o comportamento dos sólidos foram avaliados sob condições naturais de radiação, temperatura e características dos efluentes. As condições operacionais foram as seguintes: 50 mg L-1 de ferro, pH 5, 525 mg L-1 de H2O2, administrados em dosagens decrescentes. O oxalato foi adicionado na razão molar de 1:3 [Fe+3:(C2O4)-2]. A descoloração máxima de E1 foi de 67% para intensidade de radiação de 690 W m-2; já a de E2 foi de 95% para intensidade de 620 W m-2. Houve considerável aumento na turbidez e nos sólidos suspensos em função da precipitação do ferro e de sua ação coagulante. A degradação do complexante durante o processo no E2 em dias ensolarados provocou elevada sedimentabilidade dos sólidos do efluente final, resultando em um sobrenadante clarificado, o que não ocorreu em dias nublados.

ABSTRACT This work evaluates the solar photo-Fenton process mediated by ferrioxalate as a primary treatment of raw textile effluent (E1) and as a polishing step, after active sludge process (E2). For a year, at least once a month, the color removal's efficiency and solids' behavior in the oxidative process treatment were analyze under natural conditions of light, temperature and effluents characteristics. The operational parameters values were: 50 mg L-1 iron, pH 5, 525 mg L-1 H2O2, introduced in decreasing doses. The oxalate was added at the molar ratio of 1:3 [Fe+3:(C2O4)-2]. The color removal of E1 was 60% for 690 W m-2 of radiation intensity and 95% for 620 W m-2 intensity to E2. Considerable increases were observed in turbidity and suspended solids due to the iron precipitation and the consequent coagulant action. In sunny days, the complex degradation in E2 resulted in high settle ability of solids in the final effluent, resulting in a clear supernatant. This has not happened in cloudy days.

Comparative study on treatment performance, membrane fouling, and microbial community profile between conventional and hybrid sequencing batch membrane bioreactors for municipal wastewater treatment.

A sequencing batch conventional membrane bioreactor (SB-CMBR) and sequencing batch hybrid membrane bioreactor (SB-HMBR) were operated in parallel under two different hydraulic retention times (HRTs) (namely 12 h and 6 h), and their chemical oxygen demand (COD) and nutrient removal performance, membrane fouling behavior, and microbial community characteristics were compared. Both systems exhibited high organic matter (> 95%) and ammonium (> 98%) removal performance regardless of the HRT applied. As the HRT was reduced from 12 to 6 h, total nitrogen removal slightly increased in both reactors, being higher in the carrier-based MBR, where anoxic zones may have been established within the biofilm. Conversely, total phosphorus removal improved only in the SB-CMBR at the shorter HRT. Moreover, activity batch assays have shown a faster P uptake rate in the SB-CMBR than in the SB-HMBR, a result likely associated with the lower relative abundance of phosphate-accumulating organisms in both adhered and suspended biomass fractions in the hybrid MBR. The results also revealed that more pronounced increases in the transmembrane pressure and, consequently, in the membrane fouling rate at higher COD loading rates were observed in the SB-CMBR, where the soluble microbial products (proteins, polysaccharides, and especially, transparent exopolymer particles), supernatant turbidity, and filamentous bacteria were more significant. Overall, as compared to the conventional MBR, the plastic media-based SB-HMBR showed a lower fouling propensity at all hydraulic conditions tested.

Desinfecção de efluentes sanitários através de dióxido de cloro / Disinfection of domestic wastewater using chlorine dioxide

A desinfecção dos esgotos deve ser considerada quando se pretende reduzir os riscos de transmissão de doenças infecto-contagiosas. Nesse sentido, os requisitos de qualidade de uma água devem ser avaliados em função dos usos previstos para a mesma. O dióxido de cloro (ClO2) possui excelentes propriedades bactericidas, virucidas, esporocidas e algicidas e, devido a isso, é usado como desinfetante de água de abastecimento e efluente doméstico, bem como inibidor de crescimento de algas. O objetivo do trabalho foi estudar a melhor dosagem para uma boa desinfecção de efluentes sanitários previamente tratados mediante lodos ativados por aeração prolongada, avaliar a inativação de coliformes e o residual de dióxido de cloro remanescente. Foram realizados ensaios para diferentes dosagens de dióxido de cloro e diferentes tempos de contato. Os resultados obtidos mostraram que a dosagem mais indicada para desinfecção do efluente estudado foi 2,0 mg ClO2/L com um tempo de contato de 20 minutos, condições sob as quais é atingido 100 por cento de remoção de coliformes fecais e oxidada parcialmente a matéria orgânica remanescente, em tanto que os valores de pH e residual de ClO2 do efluente mantêm-se dentro dos admitidos pelas normativas brasileira e estadunidense em vigor. O estudo econômico levado a cabo permitiu concluir que a desinfecção de efluente doméstico mediante dióxido de cloro pode ser economicamente viável.

Aqueous and solid complexes of iron(III) with hyaluronic acid. Potentiometric titrations and infrared spectroscopy studies.

The coordination of iron(III) ion to hyaluronic acid (Hyal) in aqueous solutions and solid state was accomplished by potentiometric titrations and infrared spectroscopy. The potentiometric titration studies provided the binding constants for the complexes found in the systems and the speciation of these species according to the variation of pH values. The complexes found presented a complexing ability through both the chelating moieties of Hyal (via the N-glucosamine and D-glucoronic acid), showing no special preference for either one while in solid state, but when in aqueous solution the complexation via the N-glucosamine moiety was the preferred, forming two complexed species, ML and ML(2) (log K(ML)=8.2 and log K(ML2)=7.9). The presence of a mu-oxo complex via the D-glucoronic acid was also detected in both aqueous (log K=6.7) and solid states via the N-glucosamine and D-glucoronic acid simultaneously linked to two Hyal chains. A structure for this latter complex was suggested. The results indicated that these complexes could be used in eliminating the excess iron(III) in living organisms.