In Mirzapur (U.P.), a power-starved district, the UASB (Upflow Anaerobic Sludge Blanket) technique was adopted. Almost all of the available technologies do not treat heavy metals, so, is the case with the UASB also. The present study is to assess how much heavy metal can get accumulated in plant tissues in different species. The result of the present study was that the concentration of Pb(1106.31)>Zn(221.45)>Cd(49.26)>Hg(23.37) mg/Kg in the sludge while the concentration of Zn(93.35)>Pb(52.00)>Hg(16.93)>Cd(1.53) mg/Kg in the soil. When the sludge was mixed with the soil the trend got changed and the trend was Pb(596.36)>Zn(219.86)>Cd(24.70)>Hg(22.63) mg/Kg. Three different species that were chosen for the study were Basella Alba (Spinach), Solanum Lycopersicum (Tomato) & Brassica Juncea (Mustard). The trend of accumulation of studied heavy metals in the Brassica Juncea (Mustard) was Zn(85.33)>Pb(25.88)>Hg(11.23)>Cd(0.99) mg/Kg. In Solanum lycopersicum (Tomato) the trend was Pb(231.11)>Zn(108.72)>Hg(12.43)>Cd(9.41) mg/Kg  and in Basella alba (Spinach) was Zn(103.81)>Pb(83.90)>Hg(10.78)>Cd(4.18) mg/Kg. Overall the study reveals that the accumulation of heavy metals takes place in plants grown in soil mixed with sewage sludge. The reduction in the concentration of Pb, Cd, Hg and Zn in sludge mixed with soil after the harvesting of plant in case of Solanum lycopersicum were 39.38%, 47.93%, 6.18% and 49.89% respectively; while in case of Basella alba these were 25.23%, 57.53%, 71.58% and 49.16% respectively; and in case of Brassica Juncea these reduction were 25.86%, 60.80%, 70.96% and 49.04% respectively.

Developing low-cost and high-performance biosorbent for water purification continues drawing more and more attention. In this study, cellulose-chitosan composite hydrogels were fabricated via a co-dissolution and regeneration process using a molten salt hydrate (a 60 wt% aqueous solution of LiBr) as a solvent. The addition of chitosan not only introduced functionality for metal adsorption but also increased the specific surface area and improved the mechanical strength of the composite hydrogel, compared to pure cellulose hydrogel. Batch adsorption experiments indicated that the composite hydrogel with 37% cellulose and 63% chitosan exhibited an adsorption capacity of 94.3 mg/g (1.49 mmol/g) toward Cu²⁺ at 23 °C, pH 5, and initial metal concentration of 1500 mg/L, which was 10 times greater than the adsorption capacity of pure cellulose hydrogel. Competitive adsorption from a mixed metals solution revealed that the cellulose-chitosan composite hydrogel exhibited selective adsorption of the metals in the order of Cu²⁺ > Zn²⁺ > Co²⁺. This study successfully demonstrated an innovative method to fabricate biosorbents from abundant and renewable natural polymers (cellulose and chitosan) for removing metal ions from water.

In this study, the biochar (BC) supported Fe–Cu bimetallic stabilized by PVP (Fe–Cu/PVP/BC) were prepared and utilized to enhance the nitrate (NO₃⁻) removal and the selectivity toward nitrogen (N₂). Results showed the optimum Fe:Cu:BC ratio and the dosage of the BC (pyrolysis at 700 °C) supported Fe–Cu bimetallic stabilized by polyvinylpyrrolidone (PVP) (Fe–Cu/PVP/BC₇₀₀) were respectively 1:2:3 and 1 mg L⁻¹ with the selectivity toward N₂ of 31 %. This was mainly due to the synergy among Fe⁰, Cu⁰ and BC in the Fe–Cu/PVP/BC. The addition of Fe⁰ could reduce the NO₃⁻ through providing electron. The Cu⁰ and BC improved the selectivity of NO₃⁻ to N₂ through forming [Cu–NO₂⁻ₐdₛ] and adjusting redox potential. The addition of Fe–Cu/PVP/BC could supply electrons for denitrification and enhance the relative abundances of Azospira and Thauera related to denitrification to improve NO₃⁻ removal. This result was further confirmed by the variations of denitrifying functional genes (narG, nirK, nirS and nosZ). This research provided an effective method to improve NO₃⁻ removal during surface water treatment in constructed wetlands (CWs) by adding Fe–Cu/PVP/BC.

Metal-organic frameworks (MOFs) are an emerging class of materials which have garnered increasing attention for their utility as adsorbents and photocatalysts in water treatment. Nevertheless, the environmental risks of MOFs, especially their underlying impacts on aquatic organisms, are not fully explored. Herein, the toxicity of multiple representative MOFs was systematically assessed using a freshwater green alga (Chlamydomonas reinhardtii) model. Six typical MOFs with different metal nodes or organic linkers, including four transition metal incorporated aluminum-based porphyrin MOFs [pristine Al-PMOF, Al-PMOF (Cu), Al-PMOF (Ni), and Al-PMOF (Co)], one amine-functionalized MOF NH₂-MIL-125 (Ti), and one bimetallic Hofmann MOF (NiCo-PYZ), were successfully synthesized and characterized. All the tested MOFs significantly reduced the chlorophyll content and inhibited the algal growth, with the most toxic materials being NiCo-PYZ and Al-PMOF (Cu). Distinct toxic mechanisms were observed for the tested MOFs. Metal ion release was the primary cause for algal toxicity induced by NiCo-PYZ. The algal toxicity induced by porphyrin MOFs could be explained by the combined effects of metal ion release and nutrient adsorption, agglomeration and physical interactions, and reactive oxygen species generation. NH₂-MIL-125 (Ti) showed higher stability and more biocompatibility than the other tested MOFs. MOFs concentrations with no harmful effects to algae can be taken as the threshold values for safe use and discharge of MOFs. The ecotoxicological risks of MOFs should be considered as the applied concentrations of MOFs at mg/mL levels in environmental remediation were much higher than the no harmful effect thresholds.

Selective removal of arsenic (As) is the key challenge for any of As removal mechanisms as this not only increases the efficiency of removal of the main As species (neutral As(III) and As(V) hydroxyl-anions) but also allows for a significant reduction of waste as it does not co-remove other solutes. Selective removal has a number of benefits: it increases the capacity and lifetime of units while lowering the cost of the process. Therefore, a sustainable selective mitigation method should be considered concerning the economic resources available, the ability of infrastructure to sustain water treatment, and the options for reuse and/or safe disposal of treatment residuals. Several methods of selective As removal have been developed, such as precipitation, adsorption and modified iron and ligand exchange. The biggest challenge in selective removal of As is the presence of phosphate in water which is chemically comparable with As(V). There are two types of mechanisms involved with As removal: Coulombic or ion exchange; and Lewis acid-base interaction. Solution pH is one of the major controlling factors limiting removal efficiency since most of the above-mentioned methods depend on complexation through electrostatic effects. The different features of two different As species make the selective removal process more difficult, especially under natural conditions. Most of the selective As removal methods involve hydrated Fe(III) oxides through Lewis acid-base interaction. Microbiological methods have been studied recently for selective removal of As, and although there have been only a small number of studies, the method shows remarkable results and indicates positive prospects for the future.

Water treatment and reuse initiatives are essential to combat declining water supplies in a changing climate, especially in arid and semi-arid regions. Pollution of water resources intensifies the search for strategies to provide water for potable and non-potable reuse that mitigates detrimental ecological and human health effects. Fipronil and synthetic pyrethroids are common urban-use insecticides that exert aquatic toxicity at trace levels and have been often found in urban surface streams. In this study, samples were collected from the 182 ha Prado Wetlands in Southern California for seven months to assess the occurrence of fipronil and its degradation products as well as pyrethroids (bifenthrin and cyfluthrin) in water, sediment, and plants in a 4.45 ha vegetated surface flow constructed wetland (CW). Concentration-based removal values and changes in mass flux were calculated to determine the efficacy of CW treatment. Observed water concentrations were further used to calculate toxic units for the invertebrates Hyalella azteca and Chironomus dilutus. Pesticide concentrations in water, sediment, and plant samples consistently decreased during passage through the CW at all time points. Removal values for fipronil desulfinyl, fipronil sulfide, fipronil, fipronil sulfone, bifenthrin, and cyfluthrin were 100%, 99.7–100%, 57.8–88.1%, 75.6–100%, 74.7–100%, and 36.6–82.2%, respectively, and there was a general net deposition of pesticides into CW compartments. Toxic unit values decreased in every instance for both aquatic invertebrates. Settling of contaminated particles, adsorption to sediment, plant uptake or adsorption, and subsequent degradation contributed to the effective removal of these urban-use insecticides, which highlights the potential of CWs for protecting urban water quality.

Microplastic (MP) has been detected ubiquitously in freshwater systems. Until now MP sampling, however, is predominantly based on short-term net or pumping and filtration systems which can only provide snapshots of MP abundance; especially in flowing water bodies. To improve representativeness in the determination of MP occurrences in these aquatic compartments, an integrative approach that covers larger water volumes for a longer period of time is required. In this regard, surface water supplied drinking water treatment plants (DWTPs) represent an opportunity. In DWTPs, suspended solids from thousands of cubic metres of raw water are continuously removed over several hours and enriched in coagulation/flocculation and filtration processes. Our hypothesis was that MP is also removed to a full extent, like suspended solids, and that an integrative approach for identification and quantification in raw water can be derived from the analysis of MP in the treatment sludge. To prove this hypothesis, treatment sludge from a riverside DWTP (Warnow river, North-Eastern Germany) was analysed for MP > 50 μm. A sample purification protocol overcoming potential matrix effects caused by coagulants and flocculants was developed and validated. MP was analysed using micro-Raman spectroscopy. MP occurrence determined for the Warnow river was compared with in situ reference sampling using an established pumping and filtration system at relatively stable flow conditions. As result, the number of MP particles derived from treatment sludge was extrapolated to 196 ± 42 m⁻³ for the Warnow river and is statistically insignificantly different from 233 ± 36 m⁻³ identified by conventional water sampling. In addition, the polymer distribution and particles shape indicated the validity of the integrative concept. Consequently, the determination of MP abundance for freshwater systems based on DWTP treatment sludge represents an adequate method to estimate MP concentrations in flowing waters in an integrative way.

This study provided a monitoring of phenolic compounds occurrence in a river and in its treated water by a conventional water treatment plant (WTP) throughout a year-period, in Minas Gerais - Brazil. Furthermore, the environmental risk (hazard quotient - HQ), the human health risk (margin of exposure - MOE), and the cancer risk were calculated for the compounds. The results indicated that sixteen out of the seventeen investigated phenolic compounds were detected at some point during the sampling campaign. The most frequent compounds in the raw surface water were 2,3,4–trichlorophenol (234TCP), 2,4–dimethylphenol (24DMP), and 4–nitrophenol (4NP), whereas in treated water were 4NP and bisphenol A (BPA). In addition, the highest total concentration values were corelated to the months in which there was less precipitation, demonstrating that the presence of this micropollutants may be subject to seasonality. From the treated water results, it was not possible to state the efficiency of the conventional WTP in eliminating the phenols, since in some samples the phenolic compounds were totally removed and in others their increase or formation occurred. Regarding to the risk assessments, most of the evaluated compounds were considered highly toxic to some trophic level and posed a significant human health risk. Additionally, the risk reduction of phenolics using conventional WTP was low.The sixteen phenols contamination in surface and drinking waters appears to be subject to seasonality. Besides that, an alarming risk for environment and human health was identified.

Trace organic compounds (TOrCs) and microplastics (MPs) have been recognized as emerging pollutants that cause severe water pollution related problems due to their non-degradable and bio-accumulative nature. Many studies on oxidation processes such as ozone have been conducted to efficiently remove TOrCs in water treatment. However, there has been a lack of research on the removal efficiency of TOrCs in the oxidation process when they co-exist with MPs and form transformation byproducts (TBPs) during this process. This study evaluates the effects of MPs on TOrC removal during ozonation at various ozone concentrations and based on the mass of MP particles in distilled water. The adsorption of TBPs and TOrCs was also evaluated using the Freundlich and Langmuir isotherm equations. The toxicity of these compounds was evaluated to confirm the risk to aquatic ecosystems. The results show that triclosan (TCS) had the highest absorption capacity amongst the TOrCs and TBPs tested. Polyvinylchloride exhibited the highest adsorption efficiency compared with polyethylene and polyethyleneterephthalate (TCS 0.341 mg/g) due to its high adsorption capacity and hydrophobicity. In the toxicity test, 2,4-dichlorophenol and 4-chloroaniline as TBPs had a relatively higher toxicity to Vibrio fischeri (a marine bacterial species) than Daphnia magna (a freshwater plankton species).

To meet human food and fiber needs in an environmentally and economically sustainable way, we must improve the efficiency of waste, water, and nutrient use by converting vast quantities of agricultural and food waste to renewable bioproducts. This work converts waste cherry pits, an abundant food waste in the Great Lakes region, to biochars and activated biochars via slow pyrolysis. Biochars produced have surface areas between 206 and 274 m²/g and increased bioavailability of Fe, K, Mg, Mn, and P. The biochars can be implemented as soil amendments to reduce nutrient run-off and serve as a valuable carbon sink (biochars contain 74–79% carbon), potentially mitigating harmful algal blooms in the Great Lakes. CO₂-activated biochars have surface areas of up to 629 m²/g and exhibit selective metal adsorption for the removal of metals from simulated contaminated drinking water, an environmental problem plaguing this region. Through sustainable waste-to-byproduct valorization we convert this waste food biomass into biochar for use as a soil amendment and into activated biochars to remove metals from drinking water, thus alleviating economic issues associated with cherry pit waste handling and reducing the environmental impact of the cherry processing industry.