Formation of trihalomethanes (THMs) through excessive chlorination in the supplied water and its carcinogenic nature is a public health concern in many parts of the world, including a couple of neighboring countries in Asia. However, the issue was not yet addressed either in the public health policy or in academia in Bangladesh. Therefore, the objectives of this study are to determine the THM concentration in supplied water, its multiple pathways to the human body, and an estimation of resultant carcinogenic risk to urban dwellers in six different regions of Dhaka city. Thirty-one supplied water samples were collected from 31 different water points located in Purana Paltan, Naya Paltan, Kallyanpur, Shyamoli, Malibagh-Rampura, and Panthapath regions in premonsoon time. Total chlorine and chlorine dioxide (ClO₂) and trihalomethane (THM) concentration were determined using UV-VIS spectrophotometer; total organic carbon (TOC), total inorganic carbon, and total carbon concentration were measured using TOC analyzer, and chloroform concentration was determined by applying gas chromatography-mass spectroscopy (GC-MS-MS) in the supplied water samples. Research findings indicate that THM concentration exceeded the USEPA acceptable limit (80 ppb) in all regions except Panthapath. Study results showed that carcinogenic risk via ingestion was higher than the USEPA acceptable limit of 10⁻⁶. Carcinogenic risk via dermal absorption and inhalation exposure was lower according to USPEA acceptable limit. To conclude, this study represents the current knowledge about THM concentration in supplied pipeline water and adverse health risk, which signifies that regulatory measures should be taken to reduce the THM concentration.

In this study, we investigated the Sb(V) adsorption on ferrihydrite (Fh) at different pH values, in the presence and absence of common competing anions in soil such as phosphate (P(V)) and arsenate (As(V)). Batch adsorption experiments, carried out at pH 4.5, 6.0, and 7.0, showed a greater affinity of Fh towards P(V) and As(V) with respect to Sb(V), especially at higher pH values, while the opposite was true at acidic pH. The capacity of Fh to accumulate greater amounts of phosphate and arsenate in the 6.0–7.0 pH range was mainly linked to the different acid properties of P(V), As(V), and Sb(V) oxyanions. The Sb(V) adsorption on Fh was highly pH-dependent and followed the following order: pH 4.5 (0.957 mmol·g⁻¹ Fh) > pH 6.0 (0.701 mmol·g⁻¹ Fh) > pH 7.0 (0.583 mmol·g⁻¹ Fh). Desorption of antimonate from Sb(V)-saturated Fh, treated with citric and malic acid solutions, was ~equal to 55, 68, and 76% of that sorbed at pH 4.5, 6.0, and 7.0, respectively, while phosphate, arsenate, and sulfate were able to release significantly lower Sb(V) amounts. The FT-IR spectra revealed substantial absorbance shifts related to the surface hydroxyl groups of Fh, which were attributed to the formation of Fe-O-Sb(V) bonds and supported the formation of inner-sphere bonding between Sb(V) and Fh.

The air pollution problem in Xingtai and Handan is the focus of public attention. The seasonal gray model with fractional order accumulation is proposed to predict the quarterly concentrations of PM₂.₅, PM₁₀, NO₂, and CO in Xingtai and Handan. The new model has higher forecasting performance and can describe the characteristics of seasonal fluctuation very well. The forecasting results indicated that except for the PM₁₀ in Xingtai that will increase slowly, the other indicators in the two places will decrease. The changes of the air quality indicator concentration in different quarters are obvious, and in the same quarter tend to be stable. Except for CO and NO₂ in some seasons, other indicators are in the state of exceeding the standard. The effect of air pollution control is not good. The governance needs to be further strengthened.

This study investigated the growth-dependent role of algal organic matters (AOMs) to achieve high removal efficiency (R.E) of microalgae. The results showed that the microalgae cells produced 96 ± 2% of total AOMs as loose bound AOMSS (LB-AOMs) and 4 ± 1% as cell-bound (CB-AOMs) in exponential phase. In stationary phase, LB-AOMs and CB-AOMs were 46 ± 0.7percentage and 54 ± 0.2 percentage, respectively. The R.Es in exponential and stationary phase were 83 ± 2.6% and 66 ± 1.2%, respectively. It is found that the difference of biomass concentration (between exponential and stationary phase) had no significant impact on the R.E (P > 0.01). Further investigations revealed that LB-AOMs inhibit flocculation in exponential and CB-AOMs in stationary phase; however, CB-AOMs showed stronger inhibition than the LB-AOMs (P < 0.01). The provision of calcium (17 ± 0.9 mg/L) to the culture reduced the AOMs inhibition and improved the R.E from 66 ± 1.2% (in control) to 90 ± 4.2%. An increase in R.E was attributed to the interaction of calcium with AOMs and subsequently acting as a flocculant. The findings of this study can be valuable to improve the performance of auto-flocculation technology, which is mainly limited by the presence of AOMs. Graphical Abstract

Huge amounts of natural bischofite (MgCl₂∙6H₂O) resulting from the mining process of salt lakes often cannot be utilized effectively and are discarded; techniques for reutilization of the discarded bischofite as magnesium resources are limited. The nano-magnesium hydroxide (nano-Mg(OH)₂) synthesized from natural bischofite was firstly used as catalyst for ozonation of antibiotics including sulfathiazole (ST), ofloxacin (OFL), and tetracycline (TC). Rapid ozonation of ST, OFL, and TC was achieved using nano-Mg(OH)₂ as catalyst. The removal rate constant of OFL in the catalytic ozonation treatment (kOFL = 0.512 min⁻¹) was nearly 2.1 times higher than the single ozonation (kOFL = 0.249 min⁻¹). The removal rate constant of ST and TC increased by 23.5% and 32.8% from 0.298 min⁻¹ and 0.384 min⁻¹ to 0.368 min⁻¹ and 0.510 min⁻¹, respectively, when the catalyst was added into the reaction system. The removal rate constant of ST sharply increased from 0.259 to 0.604 min⁻¹ when the reaction temperature increased from 15 to 35 °C while those of OFL and TC changes slightly. The removal efficiency sharply decreased when the initial concentration of ST, OFL, and TC increased from 10 to 500 mg L⁻¹. Both anions and cations could inhibit the removal of ST, OFL, and TC at relatively higher concentrations. The prepared nano-Mg(OH)₂ catalyst could maintain its catalytic activity in the repeated use process. High removal efficiency of typical antibiotics and heavy metals free indicated that nano-Mg(OH)₂ from natural bischofite is a promising ozonation catalyst in terms of antibiotics removal.

Since the introduction of environmental legislations and directives, the impact of combined sewer overflows (CSO) on receiving water bodies has become a priority concern in water and wastewater treatment industry. Time-consuming and expensive local sampling and monitoring campaigns are usually carried out to estimate the characteristic flow and pollutant concentrations of CSO water. This study focuses on estimating the frequency and duration of wet-weather events and their impacts on influent flow and wastewater characteristics of the largest Italian wastewater treatment plant (WWTP) located in Castiglione Torinese. Eight years (viz. 2009–2016) of historical data in addition to arithmetic mean daily precipitation rates (PI) of the plant catchment area are elaborated. Relationships between PI and volumetric influent flow rate (Qᵢₙ), chemical oxygen demand (COD), ammonium (N-NH₄), and total suspended solids (TSS) are investigated. A time series data mining (TSDM) method is implemented with MATLAB computing package for segmentation of time series by use of a sliding window algorithm (SWA) to partition the available records associated with wet and dry weather events. According to the TSDM results, a case-specific wet-weather definition is proposed for the Castiglione Torinese WWTP. Two significant weather-based influent scenarios are assessed by kernel density estimation. The results confirm that the method suggested within this study based on plant routinely collected data can be used for planning the emergency response and long-term preparedness for extreme climate conditions in a WWTP. Implementing the obtained results in dynamic process simulation models can improve the plant operational efficiency in managing the fluctuating loads.

Pesticides are used worldwide in farming activities to guarantee crop yields. In southeastern Mexico, groundwater is the primary source of water for humankind. However, because of the soil characteristics and of intensive agricultural practices, the aquifer is vulnerable to pollution as shown by the regular detection of pesticide residues in groundwater. Within this context, the dissipation and adsorption of four of most used pesticides (2,4-D, atrazine, diazinon, and glyphosate) by farmers in southeastern Mexico were studied to determine their fate in agricultural soil and estimate their risk for the aquifer. Forty-one days after their application, the four pesticides were entirely dissipated from the soil. 2,4-D and glyphosate were the most persistent according to DT₅₀. Diazinon was the most adsorbed to the soil at equilibrium time. All pesticides were volatilized in substantial amounts, reaching 10.1, 22.3, 22.4, and 43.4% of initial amount 72 h after application of glyphosate, atrazine, 2,4-D, and diazinon, respectively. Volatilization was dependent on time and pesticide type (P < 0.05). Following their KOC, diazinon and glyphosate were found to be the most prone to leach. Therefore, in the absence of mitigation measures, their use represents a significant threat for the groundwater in Southeastern Mexico.

Volatile organic compounds (VOC) are air pollutants usually found in urban and industrial areas. Heterogeneous photocatalysis is an interesting technique used to degrade these compounds. Several approaches may enhance this process; some studies have shown higher VOC conversions by adding ozone to the experimental system, once ozone increases the number of reactive radicals in the reaction. In this context, this work studied the conversion of cyclohexane and toluene by heterogeneous photocatalysis in gas phase, in the presence of titanium dioxide (TiO₂), UV light, and different concentrations of ozone. For fixed space times from 13.1 to 48.8 s, an average increase of 9% was reached in cyclohexane conversion when comparing the system with maximum concentration of ozone (0.8%) and the system without it. In addition, difference of less than 2% in the conversion of cyclohexane with different moisture fractions was observed. Toluene photodegradation was also analyzed in the presence of ozone and although the conversion was only about 40% for the space time of 25 s, this result was maintained during 4 h of experiment, with no catalyst deactivation as usually reported in the literature for aromatic compounds. Based on the results, ozone addition is an advantageous technique to improve the photodegradation of VOC.

The presence of potentially toxic metals such as Cu(II) and Pb(II) in aquifers and industrial effluents represents a serious health problem due to their high toxicity, non-biodegradability, and ability to bioaccumulate. In this study, the removal of these pollutants individually and as a binary mixture has been studied, using solid coffee waste modified with 0.6 M citric acid as the adsorbent, and a mathematical model based on the ion exchange mechanism was implemented to elucidate the adsorption equilibrium. The characterization of modified coffee waste showed a pH value at the point of zero charge of 2.97 and a high concentration of carboxylic groups, which are susceptible to ion exchange. Furthermore, the quantification of interchangeable ions confirmed that the main mechanism of adsorption is the ion exchange of metal ions with the protons present on the adsorbent’s surface. The experimental data of the individual and binary adsorption equilibrium using a model based on a phenomenological approach was analyzed. The phenomenological model was compared with the Freundlich and Langmuir empirical solid-liquid adsorption models. The results showed that the adsorption capacities of Cu(II) and Pb(II) individually were 1.46 and 1.18 meq/g, and in a binary mixture were 1.43 and 1.24 meq/g, respectively, at pH 5 and 30 °C. In addition, the separation coefficients from ion exchange model revealed the predominance of protons as an exchangeable ion, which is in accordance with the experimental evidence. Finally, the correlation coefficient showed that the proposed model predicts accurately the adsorption equilibrium.

The denitrifying anaerobic methane oxidation (DAMO) process can achieve methane oxidation and denitrification at the same time by using nitrate or nitrite as an electron acceptor. The short- and long-term effects of nitrite on DAMO organisms were studied from macro (such as denitrification) to micro (such as microbial structure and community) based on two types of DAMO microbial systems. The results showed that the inhibitory effects of nitrite on the two DAMO microbial systems increased with rising concentration and prolonged time. In the short-term inhibitory phase, nitrite with concentrations below 100 mg N L⁻¹ did not inhibit the two distinct DAMO enrichments. When nitrite concentration was increased to 950 mg N L⁻¹, the nitrogen removal performance was completely inhibited. However, in the long-term inhibition experiment, when nitrite concentration was increased to 650 mg N L⁻¹, the nitrogen removal performance was completely inhibited. In addition, in acidic conditions, the real inhibitor of nitrite is FNA (free nitrous acid), while in alkaline conditions, the real inhibitor is the ionized form of nitrite. By using high-throughput sequencing technology, the species abundance and diversity of the two DAMO microbial systems showed an apparent decrease after long-term inhibition, and the community structure also changed significantly. For the enrichment culture dominated by DAMO bacteria, the substantial drop of Methylomonas may be the internal cause of the decreased nitrogen removal rate, and for the coexistence system that hosted both DAMO bacteria and archaea, the reduction of Nitrospirae may be an internal reason for the decline of the denitrification rate.