Sewage pollution: genotoxicity assessment and phytoremediation of nutrients excess with Hydrocotyle ranunculoides

Performance of basalt fiber-periphyton in deep-level nutrient removal: A study concerned periphyton cultivation, characterization and application

Nutrients in centralized discharge area of treated sewage can cause high ecological risks to aquatic systems, thus a deep-level nutrient removal is necessary. Recently, periphyton has attracted increasing interests for its excellent performance in nutrient removal. In this study, the suitability and durability of basalt fiber (BF) as a new green carrier of periphyton was evaluated, and development process of basalt fiber-periphtyon (BFP) was tracked with bacterial community succession and physiological indicators. Then, well-developed BFP was applied to deeply purify water containing the same concentration of nutrient as the treated sewage. Results showed the periphyton could adapt to BF and formed in large quantities. In addition, the tensile strength of BF after being used as a carrier was still strong. Bacterial community and physiological indicators indicated that BFP was well developed in 40-50 days. LEfSE and random forest analysis revealed that Deinococcus-Deinococci, Spartobacteria and Chlamydiia at class-level, Rhizobiales and Rhodobacterales at order-level were the biomarkers for development of BFP. Moreover, application results showed BFP efficiently removed nitrogen and phosphorus from water and promoted the transformation of ammonia to nitrate. The concentration of ammonia and phosphorus severely decreased from 4.90 ± 0.11 mg/L to 0.51 ± 0.20 mg/L, from 0.66 ± 0.016 mg/L to 0.023 ± 0.013 mg/L, respectively. The efficient nutrient removal was attributed to accumulation of nitrogen and phosphorus metabolism related organisms in BFP as well as favorable water physic-chemical conditions created by BFP. These results suggest that BF is a suitable and durable green carrier of periphyton, and BFP could efficiently reduce ecological risk to aquatic systems receiving treated sewage.

Development and testing of a 3D-printable polylactic acid device to optimize a water bioremediation process

In the present work, a remediation bioprocess based on the use of a native isolate of Chlorella vulgaris immobilized in an alginate matrix inside a polylactic acid (PLA) device is proposed. This microalga immobilized in alginate beads was previously shown to be useful for the reduction of several chemical and microbial contaminants present in the highly polluted water from the Matanza-Riachuelo watershed. However, these beads had a relatively short shelf life in the natural environment. To overcome this limitation, a 3D-printed PLA device was designed. PLA is a biocompatible and biodegradable material suitable for biotechnological applications. We used Erlenmeyers and stirred-tank bioreactors fed batch with Murashige Skoog (MS) culture medium or water from the Cildáñez stream (one of the water bodies of the aforementioned watershed) to estimate the growth kinetics parameters and the bioremediation capacity of immobilized-microalgal cells as an unconfined system (UcS) or a confined system (CfS) inside PLA devices on Cildáñez water. Although alga's growth parameters were maximum in the UcS fed with MS medium as substrate, successful bioremediation of the target water was possible using the CfS: all inorganic nitrogen forms and total phosphorus were reduced at least by 90% after 5 days of bioprocess in an agitated bioreactor, whereas aerobic mesophilic bacteria decreased by about 85%. The number of coliforms also decreased. Standardized cytotoxicity tests using Allium cepa seeds carried out to prove the effectiveness of the bioremediation process, confirmed the high degree of decontamination achieved by the use of immobilized microalga confined in a 3D-printable PLA-device.

Genotoxicity of water samples from an area of the Pampean region (Argentina) impacted by agricultural and livestock activities

The aim of this study was to assess the genotoxic potential of surface waters located in a rural area in the north east of Buenos Aires province (Argentina) using the Allium cepa test. Water samples were collected at four sites located in a drainage channel and two sites on the Burgos stream that receives water from the channel, taking into account the sowing and harvesting months and rainfall periods. Analytical determinations revealed high total concentrations of Cd, Cu, Pb, and Zn (maximum values: 0.030, 0.252, 0.176, and 0.960 mg L-1, respectively), and concentrations of glyphosate and its metabolite aminomethylphosphonic acid (AMPA), with maximum values of 13.6 and 9.75 μg L-1, respectively. Statistically positive correlations were observed between the total metal concentrations and precipitation. No cytotoxicity (mitotic index MI) was observed in A. cepa. However, several water samples showed significant increases in micronucleus (MN) frequencies with respect to the controls. No correlations were observed between MN and the abiotic variables or precipitation. These results showed a state of deterioration in the water quality at the rural area studied in Buenos Aires province, and heavy metal contamination may contribute to the genotoxic activity. A. cepa was shown to be a useful tool for the detection of genotoxicity in water samples from areas with agricultural and livestock activities.

Application of common duckweed (Lemna minor) in phytoremediation of chemicals in the environment: State and future perspective

Over the past 50 years, different strategies have been developed for the remediation of polluted air, land and water. Driven by public opinion and regulatory bottlenecks, ecological based strategies are preferable than conventional methods in the treatments of chemical effluents. Ecological systems with the application of microbes, fungi, earthworms, plants, enzymes, electrode and nanoparticles have been applied to varying degrees in different media for the remediation of various categories of pollutants. Aquatic macrophytes have been used extensively for the remediation of pollutants in wastewater effluents and aquatic environment over the past 30 years with the common duckweed (L. minor) as one of the most effective macrophytes that have been applied for remediation studies. Duckweed has shown strong potentials for the phytoremediation of organic pollutants, heavy metals, agrochemicals, pharmaceuticals and personal care products, radioactive waste, nanomaterials, petroleum hydrocarbons, dyes, toxins, and related pollutants. This review covers the state of duckweed application for the remediation of diverse aquatic pollutants and identifies gaps that are necessary for further studies as we find pragmatic and sound ecological solutions for the remediation of polluted environment for sustainable development.

In situ phytoremediation characterization of heavy metals promoted by Hydrocotyle ranunculoides at Santa Bárbara stream, an anthropogenic polluted site in southern of Brazil

Aquatic environments are widely affected by anthropogenic activities and efficient remediation of these areas requires detailed studies for each natural ecosystem. This research aimed to evaluate the natural phytoremediation potential of Hydrocotyle ranunculoides L., a floating aquatic macrophyte located in a polluted aquatic environment in South of the Rio Grande do Sul, Brazil. Nutrients such as P, K, Ca, Mg, and S and heavy metals such as Cu, Zn, Fe, Mn, Na, Cd, Cr, Ni, Pb, Al, As, Co, and V content in the roots and shoots of the plants were evaluated through nitric perchloric acid digestion (HNO₃-HClO₄) methods and quantified by ICP-OES. Bioconcentration factor (BCF), translocation factor (TF), plant effective number (PEN), and potential phytoremoval (mg m^-2) were carried out. H. ranunculoides showed a substantial ability for phytoextracting P, Na, and As, since showed ability of uptake these elements from the water and translocate them to the shoots of the plants. H. ranunculoides also showed potential for application in rhizofiltration of Mg, S, Cu, Zn, Fe, Mn, Cd, Cr, Ni, Pb, Al, and V, since exhibited high potential to uptake higher levels in the roots. The highest potential for bioremoval (mg m^-2) of the H. ranunculoides was detected for K, Ca, P (recommending thus the use for phytoextraction), Fe, and Al (highly recommended for rhizofiltration). Therefore, this species under study showed high potential for in situ phytoremediation at Santa Bárbara stream, and as a widespread species, it might be tested for phytoremediation in other sites.