In most developing nations, municipal wastewater treatment is limited to aerobic secondary treatments, expensive and ineffective in removing nutrients from treated effluents before discharge, resulting in eutrophication and imbalance in receiving bodies. As a result, the effectiveness of Chlorella vulgaris for primarily treated wastewater collected from a sewage treatment plant during an 8-hour detention time was investigated in this study. Microalgae have been found to efficiently remove organics and nutrients to levels far below the desired limit in the present research. After algal treatment concentration of COD, phosphate and ammonia reduced to 12.43 mg/L (93.75%), 0.04 mg/L (98.40%) and below detectable limit (100%) respectively. In addition, remarkable reduction was found in solids (TSS, TS and TDS) and EC concentration. The use of microalgae resulted in an increase in DO concentration. As a result, introducing Chlorella vulgaris into a wastewater treatment system can lower nutrient and organics contents without any additional treatment.

This study presents a new approach to solve the one-dimensional solute transport equation with variable coefficients and two input sources in a finite porous media. The medium is divided into m-layers porous media with constant averages coefficients in each transport problem. The transport equations in layer i-1 and i are coupled by imposing the continuity of solute concentration and the dispersive flux at the interfaces of the layers. Unknown functions representing the dispersive flux at the interfaces between adjacent layers are introduced allowing the multilayer problem to be solved separately on each layer in the Laplace domain before being numerical inverted back to the time domain. The obtained solution was compared with the Generalized Integral Transform Technique (GITT) and numerical solutions for some problems of solute transport with variables coefficients in porous medium present in the literature. The results show a good agreement between both solutions for each of the studied problem. An example of application considering an advective-dispersive transport problem with a sinusoidal time-dependent emitting rate at the boundary was study in order to illustrate the effect of sinusoidal frequency on solute concentration.

Naphthenic acids are a group of polar organic carboxylic acids that are present in crude oil naturally. They are cycloaliphatic carboxylic acids which have 10 to 16 carbons, which gained importance since the early twentieth century because of corrosion in oil refineries. Moreover, they are the most important environmental pollutants caused by oil extraction from oil sand reserves. Heavy crude oils which have high concentration of naphthenic acids are usually considered as poor-quality oil and sold at a lower price. Often, the high concentration of naphthenic acids in crude oil reduces the life of the equipment which are used in the exploration and refining process because of corrosion. Hence, researchers are increasingly interested in the chemical properties of naphthenic acids and the acidic components of the crude oils. The most popular methods for the identification and analysis of naphthenic acids are liquid and gas chromatography (GC), liquid-liquid extraction, Fourier transform infrared spectroscopy (FTIR), and solid-phase extraction (SPE). Naphthenic acids are the most important environmental pollutants caused by oil extraction from oil sand reserves. Previous studies have revealed that naphthenic acids can be absorbed by fish, but their distribution in different tissues of fish has not been specified. Experimental samples showed the highest toxicity to fish, while there was less toxicity to invertebrates and algae. Moreover, naphthenates have various industrial utilizations; they are used in synthetic detergents, corrosion inhibitors, lubricants, fuel and oil additives, wood preservatives, insecticides, fungicides, pesticides, wetting agents, napalm thickening agents, and oil desiccants that are utilized in painting and treating wood surfaces.

Metals contamination in water is becoming a threat to human health. The studies ecological and health risk assessment of trace metals was conducted in seven water bodies in Akwa Ibom State, between May 2021 and April 2022 (twelve months), to evaluate the levels of trace metals contaminant and suitability of the waters for human consumption. Six trace metals were assessed in the water samples; using atomic absorption spectrophotometer after digestion. Pollution indices such as heavy metal pollution index, comprehensive pollution index, contamination index and health risk assessment for non-carcinogenic were employed. The findings were compared with Nigerian Standard for Drinking Water Quality. The mean concentration of some metals (Pb, Cd, Cr, and Cu) in some stations were exceeded the standard limits, while Fe and Ni exceeded the acceptable limits in all the stations, due to anthropogenic activities. The values for HPI in stations I, II, IV and VII were exceeded the threshold of 100, ranging between 61.4 and 743.5; CPI ranged from 1.05 to 3.72, while Cd ranged from 0.94 to 16.3, indicated that the water bodies are highly contaminated. The CDI and HQ values for Fe, Cd, Cr and Cu exceeded the oral toxicity reference dosage of contaminant and stipulated threshold (1) for HI in some stations both in children and adult, indicated that the water bodies are not suitable for human consumption. The findings call for concern regarding their effects on human health, which could be detrimental to the people drinking from these water.

Mining wastes occupy huge areas around the world, therefore, research aimed at their disposal and reclamation of disturbed territories is very relevant. We studied artificial soil based on neutralized ombrotrophic peat (Histosols Fibric) with different content (5% and 10% by weight) of copper smelting slag recycling waste ("technical sand"): finely dispersed (less than 0.05 mm), mechanically activated material. We analyzed the content of toxic element in peat, underground and aboveground parts of lawn grasses and potatoes. The coefficients of concentration and accumulation of elements were calculated. It was found that the introduction of 5% waste leads to exceeding the maximum permissible concentrations and approximately permissible concentrations (the regulated values for Russia) for zinc, copper, arsenic, antimony, and lead. The molybdenum content exceeds the Soil Quality Guidelines accepted in Canada, for selenium the values are at the limit level. The content of zinc, copper, cobalt, arsenic, molybdenum, antimony is significantly reduced (by 2-3 times) during the growing season. Ecological assessment of agricultural plants grown on artificial soil with 5% of "technical sand" showed that there are no excesses of the maximum permissible levels for any regulated element for potato tubers; a slight excess of arsenic was detected for lawn grasses. We additionally assessed the safety of potato tubers using the maximum permissible concentrations for food and established an excess of cadmium (3.4 times on the peat, with the addition of waste almost unchanged) and zinc (1.6 times on peat, 2.8 times for a peat with 10% waste).

The goal of this research was to investigate the efficacy photocatalysis with natural solar radiation and artificial UV radiation for disinfecting total coliforms in biologically treated wastewater.   The effect of TiO2 dosage and irradiation time on total coliform inactivation as measured by log reduction values (LRV), removal of BOD, COD, turbidity, and effluent properties as measured by pH and conductivity was investigated. Two sets of experimental equipment were constructed, one for using solar UV light and the other for using artificial UV light. After four hours of irradiation with 60 mg/L TiO2, photocatalysis achieved LRVs of 1.4 and 1, respectively, under UV and solar radiation. COD and BOD were reduced by 67% and 50% respectively under UV and solar radiation after two hours of irradiation with 60 mg/L TiO2. Turbidity was reduced by 71%. Both conductivity and acidity of the effluent were reduced as TiO2 concentration was increased. Photocatalysis with natural solar radiation produced disinfection results that were comparable to that of efficient UV light exposure. Artificial UV light and natural solar radiation can be combined in photocatalysis process to form a hybrid process.

Indoor air quality (IAQ) is a significant concern that affects comfort and health. It is well understood that hospitals are thermal environments in which comfort must be calibrated. This comparative study examined existing international standards of IAQ in Iranian health care facilities. A systematic review of studies on IAQ standards was conducted to test the hypothesis regarding which parameters, and at what level, can have an impact on hospital IAQ: EPA, ASHRAE, LEED, BREEAM, NIOSH, OSHA, WHO, ACGIH, Canadian, and OEL. The inclusion criteria were met by 34 of the 1886 studies that were screened from 2010-2021. The findings of the selected studies were classified into four categories for analysis: monitoring of IAQ according to standards (n=34), IAQ in healthcare facilities (n=1), impact of air pollution on human health (n=9), and interventions to improve IAQ (n=1). Based on these IAQ standards, the acceptable limit for CO2 6300 *10³ µg/m³, for CO 9000 µg/m³, for Formaldehyde 19 µg/m³, for NO2 37 µg/m³, for O3 98 µg/m³, for PM2.5 0.1 µg/m³, for PM10 10 µg/m, and for SO2 31 µg/m³ was suggested. The majority of studies conducted monitoring of pollutants in indoor environments used for homes and schools, with the majority of them relying on WHO IAQ standards. CO, PM, and NO2 concentrations have been the most studied and have the longest track record of research. The acceptable limit for IAQ parameters was proposed.

This study was conducted to assess air quality status in the selected cities of Pakistan through Air Quality Index (AQI) and Multi Pollutant Index (MPI) and their correlation. Secondary data on air pollutants’ concentrations for the year 2021 were used from the literature. For this investigation, major air pollutants including carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter were used and compared with Punjab Environmental Quality Standards. Air quality indices, Multi Pollutant Index (MPI) and the Air Quality Index (AQI) were used in the study. Overall condition of the air pollutants in the particular location was described using the Air Quality Index. For this formula, the average concentration of each pollutant across a range of time periods was first calculated. The concentration of each pollutant was then divided by the relevant standard value, which was then cumulatively averaged and represented as a percentage. Results showed that Lahore and Karachi are two of the cities with unhealthy to hazardous AQI values and poor air quality according to MPI values. Air quality is deteriorating in industrial and traffic-congested cities where pollution levels significantly exceeded the threshold values. Using the linear regression, the results confirmed the strong association between the AQI and MPI. There is a need for immediate action to be taken to lower pollutants’ concentrations and improve air quality in urban areas.

Natural quartz mineral was examined as a new sorbent for Hg(II) removal from synthetic wastewater systems. Batch adsorption experiments of Hg(II)  onto quartz mineral were conducted under various conditions such as solution pH, sorbent dosage, contact time, initial Hg(II)  concentration. Adsorption experiments results of Hg(II) by quartz mineral showed good achievement after 180 min with 1.0 g/L sorbent mass at pH of 2.0, agitation speed of 200 rpm and a temperature of 25°C. Moreover, the Hg(II) concentration was directly related to increases the adsorption capacity, the maximum Hg(II) uptake by quartz  sample was 16.52 mg/g for 80 mg/L (C0 (Hg(II)].  Langmuir isotherm and pseudo-second-order kinetics (R2 > 0.99) were found to be the most appropriate models to describe the adsorption of Hg(II) by quartz mineral. The intra-particle diffusion model and the calculated Dubinin–Radushkevich adsorption energy (Eads = 0.78 kJmol-1), confirms a physisorption adsorption reaction occurring in three stages.

The study was conducted in Lake Rinconada, a glacial lake affected by artisanal and small-scale gold mining activities in the southern Andes in Peru. The objectives of the study were to investigate the spatial distribution of heavy metals (As, Cu, Hg, Pb and Zn) in water and sediments and to assess the degree of metal pollution and ecological risk using the geoaccumulation and potential ecological risk indexes. The concentrations of As and Hg in sediments from Lake Rinconada exceeded the Canadian sediment quality regulations, whereas the concentrations of As, Hg and Pb in water and sediments from the mining-affected tributary, Lunar de Oro River exceeded the Peruvian and Canadian guidelines for water and sediments quality respectively. According to the geoaccumulation and potential ecological risk indexes, Lake Rinconada is extremely polluted by As and Hg, and the pollution is mostly concentrated in the northern part of the lake, where the mining-affected Lunar de Oro River flows into the lake. Concentrations of Pb are also high in the northern part of the lake, suggesting that the nearby gold mining town is a source of pollution. The results of this study allows to report that Lake Rinconada is completely deteriorated.