Herein, we present the results of our researches focused on obtaining composites with enhanced affinity for indigo carmine (IC) by combining two different 2D materials e.g. graphene oxide (GO) and a Cerium modified layered double hydroxide (LDH), which could act as catalysts for the oxidative removal of IC, both under ultrasonic irradiation and under conventional stirring, using H2O2 as oxidation agent. Three Mg3Al0.75Ce0.25 LDH-GO composites bearing different concentrations of GO in the range of 5-15 wt.% abbreviated as HT3Ce-xGO where x stands for the concentration of GO (x=5,10,15% wt. GO) have been prepared and characterized by XRD, SEM, Raman and DRIFT spectroscopy. The XRD patterns of HT3Ce-xGO solids have revealed the formation of nanocomposites with fine particles of CeO2 (Scherrer dimensions around 3 nm) embedded in the 2D layered structure of LDH-GO. CeO2 phase was favored by the increase in GO content for all investigated composites. The size decrease of the solid particles with the increase of GO content was proved both by SEM and DRIFT analyses. Raman spectra proved the incorporation of GO in all composites. The results of the catalytic tests showed, without any doubt the activation effect of the ultrasonic irradiation which allowed doubling the dye removal percentage (DR%) in the first 30 minutes of reaction time. For the most active catalyst, HT3Ce-15GO, the COD after 30 minutes reaction time under ultrasonic irradiation was 221 mgO2/L, while TOC was 93 mgC/L marking a decay of 61.6% for COD and 46.2% for TOC.

The municipal wastewater treatment is the source of significant amounts of primary and secondary sludge which is under the present legislation referring to quality and management aspects. It is estimated that a half of wastewater treatment plant costs are due to the sludge management. Anaerobically sludge stabilization, capitalization as energy source, in order to diminish the costs and sludge volume decreasing, are the aims of the main operational steps of sludge treatment, as a part of wastewater treatment plant. The improvement of sludge anaerobically stabilization process must be possible by acting in the rate limiting step - hydrolysis in order to rise the organic carbon solubilization. The increase of soluble carbon can be possible by adding a pretreatment step of waste biological sludge, ultrasonic disintegration being one option. This paper emphasized the experimental results regarding anaerobically stabilization of the thickened waste biological sludge by ultrasonication taking into account the results of blank test, without ultrasonication. Experimental tests show that ultrasonic disintegration of the sludge having initial dried substances content (d.w) 2.72% and soluble organic load COD of 598 mg O2/L led to soluble COD concentration of 4950-6710 mg O2/L after sonication with specific energy in the range of 3.06 - 14.24 kWh/kg d.w. Anaerobically stabilization during 25 test days at 36 0C of the mixture 40% disintegrated biological sludge and 60% digested sludge (inoculum) mixture led to 30-38.6% increase of biogas production comparing with parallel test with non-sonicated sludge.

Surface water contamination by synthetic dyes generates human and wildlife adverse health effects and causes photosynthesis decrease due to intense sun-light absorption of these pollutants. 50% of total discharged industrial effluents contain azo dyes. Congo Red is a benzidine based anionic azo dye that is usually employed in rubber, paper and plastic industries. Congo Red can cause eye and skin irritation and is potentially carcinogenic in nature. This study explores the development of a new HPLC method to detect synthetic dyes in residual waters coming from wastewater treatment technologies based on magnetic material adsorption. Cobalt ferrite (CoFe2O4) and chitosan coated cobalt ferrite (CoFe2O4-Chit) prepared by a simple co-precipitation method were tested as adsorbents for Congo Red (CR). Effect of contact time, solution pH, and initial dye concentration were studied with respect to Congo Red adsorption efficiency. The adsorption experiments were performed at pH = 4.5 and 10.8. Highest value for the removal efficiency using magnetic material of cobalt ferrite coated with chitosan (CoFe2O4-Chit) was obtained at pH 10.8

Monitoring of lakes and ponds water quality parameters is important to evaluate the interactions between quality and effects on aquatic organisms’ growth and health. Even if each water parameter individually may not be relevant, several parameters together can reveal dynamic processes that occur in the water. For instance, unbalanced pH values may increase ammonia and hydrogen sulfide toxicity. Nitrogen and phosphorus are associated with plant and algae growth, although phosphorus is generally the limiting nutrient in freshwater bodies. Accordingly, it is recommended to monitor and assess water quality parameters based on routine analyses. Therefore, the aim of this study was to generate an overview of our researches related to monitoring of water quality collected from lakes and fish ponds. The parameters on the basis of which was evaluated the quality of water were: pH, electrical conductivity (EC), total hardness (TH), chemical oxygen demand (COD), nitrate nitrogen (N-NO3-), nitrite nitrogen (N-NO2-), ammonium nitrogen (N-NH4+), phosphate phosphorus (P-PO43-).

The aim of this study was to evaluate the quality of groundwater in an area with agricultural and industrial influences, located in Valcea County. Groundwater samples were collected in 2 campaigns from 14 public wells and were analyzed for pH, conductivity (EC), arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn), copper (Cu), nitrites (NO2-), nitrates (NO3+), ammonium (NH4+) and chlorides (Cl-). In most of the studied public wells the laboratory results obtained for the physico - chemical parameters were within the limits imposed by the national legislation and those approved by the WHO. High levels of iron and manganese of natural origin were found at a public well located in a rural area and also chlorides at a well from industrial area which exceed the limits imposed.

Features of growth of microorganisms on a nutrient medium and their microscopic researches were studied. Cavitation treatment (22 kHz, 91 W, 1.65 W/сm3) of water with simultaneous action of bubbled inert gases (argon and helium) on the viability of microbial cells (Diplococcus and Sarcina) are presented. The highest water disinfection was obtained for water samples with Sarcina lutea cells for both used gases under cavitation conditions. Both investigated types of the cocci bacteria were destroyed faster under Ar/US-action after comparison of the effectiveness of the gas nature action on the water disinfection.

A direct ion chromatographic method for determination of chlorite, chlorate and bromate in the presence of fluoride, chloride, nitrate, nitrite and bromide in treated drinking waters was described. Separation of target analytes was achieved using an AS19-HC analytical column (250 mm x 4 mm), AG 19-HC guard column (50 mm x 4 mm) and KOH 25 mmol/L as mobile phase. Inorganic analytes were eluted using a flow rate of 1 mL/min. Column temperature was set up and maintained at 300C. The analyte ions were quantified using a suppressed conductivity detector.

This study investigated spatial and temporal distribution of nitrate and nitrite contaminants in groundwater from different geographical regions in Romania, with a special emphasis on a descriptive statistical analysis of data, namely determination of seasonal indices (dry season and wet season) and with establishing the standard units for the 24 of groundwater sources. Nitrate and nitrite concentration were monitored in 24 groundwater sources during the period January 2016 - February 2020 for several areas in Romania. The obtained data matrix showed that the maximum values of nitrate concentrations in different areas of Romania were the following: in the northeastern part of Romania the maximum nitrate concentration was 8.03 mg/L, in the south-eastern part of Romania, the maximum nitrate concentration was 6.37 mg/L, and in the western part towards the center of the country, following the evaluation, a maximum of nitrate concentrations of 3.55 mg/L was determined. Nitrite concentration values were <0.5 mg/L in all investigated geographical areas. The obtained data shows small changes in water quality during monitored period, which leads to the conclusion that there were no significant problems nitrate and nitrite ground water contamination. Groundwater indices allow an adequate control of water pollution, and a rigorous management of groundwater sources.

The paper aims to emphasis the specific detection of bacterial strains using enzyme-linked immunosorbent assay. The assay is based on the specific binding of polyclonal antibody anti E.coli tagged with FITC to E.coli and monoclonal antibody anti Ps. aeruginosa tagged with Alexa Fluor 647 tagged to Ps. aeruginosa and on subsequent enzymatic immunological demonstration of the conjugated enzyme. In this experiment the negative control was the Salmonella enterica strain. The two antibodies had no interaction with the negative control, instead they were specific for E . coli and Ps. aeruginosa strains. When both strains were in the same well, the fluorescence intensity given by the presence of E. coli was 2.3 times higher than that given by Ps . aeruginosa, and the intensity of fluorescence decreased if there are both bacterial strains in the wells.

Aqueous polynuclear systems have been analyzed, for which the family of formation curves intersects at a common point. The analyzed graphical and computational method for determining the stability constants can be used as initial values within the iterative calculation process. In some cases, the stability constants are calculated using only the coordinates of the common intersection point. The obtained equations could be of special interest when the experimental data can be interpreted in several models. In these cases, given the large volume of experimental data, the calculation is simple and the model can certainly be chosen with a great safety. The obtained equations may also be applied for critical evaluation of tabular data, if the coordinates of the intersection point are known. A series of real polynuclear systems have been analyzed and useful conclusions have been made.

Dams and hydraulic structures are used for the supply and control of water, which have great importance on human life. Sluice gate is one of the hydraulic control structures. Sluice gates release excessive water from the reservoir to the downstream side in a controlled manner with a certain discharge for controlling the level of reservoir. A hydraulic jump is created to dissipate energy of flow coming from under the gates. A hydraulic jump occurs when flow regime is changed from subcritical to supercritical. However, position of the hydraulic jump in channel should be known exactly in order to prevent damage to surrounding structures. In this study, an open channel system with a sluice gate is used to produce a hydraulic jump. Experiments are conducted for two different gate opening (a1=1.5 cm and a2=2 cm) and 16 discharge values. For each case position of the hydraulic jump is determined. In addition, flow depths at 5 different points were measured including before and after hydraulic jump. The results obtained from the experimental study were compared with the numerical model in terms of the position of hydraulic jump and flow depths. According to the results obtained, the numerical model and the physical model showed between 80% -91% consistency.

Broad crested weirs and steps are used to regulate the flow in the channel, increase the water level at the upstream side and measure the discharge. The construction of the broad crested weirs is more practical and also they are more stable compared with the other types of weirs. In order to serve in accordance with the purpose of their construction, broad crested weirs should be designed and built by considering certain criteria. Before the hydraulic structures are built, model experimental setups are constructed in the laboratory and problems to be encountered are tried to be determined. However there may be differences between the structure to be built in real life (prototype) and model due to scale effect. These possible differences must be determined and necessary measures must be taken. In this study, the model and prototype of the broad crested weir are constructed in two different open channel systems by using Froude similarity. Geometric similarity between model and prototype is determined as Lr=4. A total of 44 experimental data were collected from model and prototype. The results obtained from model and prototype are compared according to hydraulic similarity rules. In addition to the physical experimental setups, numerical models were created using the ANSYS Fluent for the model and prototype separately. By comparing numerical model and physical experimental setups optimum mesh size is tried to be determined. According to the results obtained from experimental setups, differences were observed in the position of critical flow depths and downstream water levels due to scale effects

A study for evaluating the quality of wastewater discharged into the sewerage network of Bucharest, for several economic agents with various activity profiles: a car wash, a sweet producer and a provider of automatic access systems, was presented in this paper. The study was conducted over a period of five years (2013-2017). The results obtained for the analyzed parameters were compared with the maximum allowed values (MAV) by the legislation in force. The results showed that for the car wash there was only one exceeding of the chemical oxygen demand (COD) parameter during the whole study period. The sweet producer and the provider of the automatic access systems evacuated wastewater with exceedances of MAV for the parameters: COD, biochemical oxygen demand (BOD5), zinc, suspended solids, extractable substances in organic solvents and total phosphorus. In order to evaluate the quality of the wastewater discharged by these two agents the quality indices of wastewater (WWQI) were calculated. For the sweet producer, the calculated water quality indices had values between 62.4 - 92.7%, with a classification of wastewater discharged in the quality class: marginal to good quality. For the provider of automatic access systems, the value of the quality index was between 74.2 and 85.5, the discharged wastewater being considered fair or good.

The chemical behavior of groundwater is one of the most dynamic areas of environmental research. In the present study, groundwater sampling from different locations in the north-west area of Romania was performed in order to assess groundwater chemistry and compare water types using Distribution maps. Groundwater chemistry has been evaluated and natural processes are identified as control factors for hydrochemistry. The Piper diagram was created to compare the results of water types. Chemical analysis of groundwater was used to calculate the values of the water quality index. Romanian drinking water standards EPA 485-2002 and WHO standards were taken into account when calculating the WQI. The SAR index was used to evaluate groundwater samples in the study area for irrigation purposes. The classification of water types based on WQI values[1,2] for each groundwater sample shows that 80% of the analyzed samples can be used as drinking water resources, the rest of 20% is intended for irrigation.

Environmental degradation related to uncontrolled development resulted in the passage of the United States Clean Water Act (CWA) in 1972, with the stated purpose “to restore and maintain the integrity of the nation’s waters”. Implementation of the CWA lead to increased research to develop multimetric indicators to better measure and understand the complex patterns of ecological responses to stress occurring across levels of biological, spatial and temporal organization. One area of research is the use of integrated indices of chemical risk, ecotoxicological risk and ecological risk to assess the impact of human activity across disturbance gradients of urbanization. Selecting relevant metrics for constructing multimetric index requires identifying bioindicator organisms with capacities to detect signals from anthropogenic disturbances. This study explored the potential efficacy of a suite of higher plant ecotoxicological assays for use as bioindicators in ecological risk assessment along a gradient of urbanization in a wetland ecosystem. The study was conducted in the Pike River watershed (Racine, Wisconsin, USA) in six wetlands selected across a gradient of dominant land use types (agricultural, commercial, residential, undeveloped and industrial). MicroBioTest Phytotoxkit TM ecotoxicological assays, based on growth inhibition of three plants (Sinapis, Sorghum and Lepidium) were used to assess sediment toxicity. The relationships between Phytotoxkit™ responses and predicted pollutant loadings calculated from surrounding landuse provided clear signals of stress from watershed pollutants draining into the wetland sites. The potential for these ecotoxicological indicators to serve as biological response signatures is strong, and further research and calibration in field and microcosms studies will assist in calibrating responses for use in integrated monitoring efforts.

In the paper are presented the results of tests on the evaluation of the level of noise and chemical air pollution in two distinct urban areas: an industrial area and an area characterized by heavy road traffic, with a focus on the novelty elements introduced by the regulations in force on the measurement and management of the level of ambient and industrial noise by periodically developing specific noise maps. The results of direct tests and noise maps developed in the case of the studied areas indicated higher values of the indicators measured in the immediate vicinity of the road artery compared to the other measuring points, highlighting the influence of vegetation in urban areas to reduce noise levels and reduce air pollution.

The research aimed to provide an optimized method for the determination of phosphorous concentration in different types of solid waste using inductive coupled plasma mass spectrometry (ICP-MS) technique. The analyzed waste matrices are: a) vegetable waste (P1), b) ash from the incineration of medical waste (P2) c) sewage sludge (P3) and d) sludge from the meat processing industry (P4). The results obtained by the ICP-MS method were compared with the UV-VIS spectrophotometric method for the determination of total phosphorus. In the case of using the colorimetric method by UV-VIS technique, lower results were obtained compared to the ICP-MS method due to the interferences given by the reagents used to determine the total phosphorus. The interferences given by other elements (metals) were also investigated and the performance parameters were determined such as detection limit, quantification limit, recovery and expandend incertainty using ICP-MS technique.

Sulfate salts which available in seawater with high concentrations cause the formation of ettringite in hydrated structures which formed as a result of the hydration of cement. On the other hand, ettringite causes excessive volume expansions and eventually leads to cracking of the concrete due to the internal stresses in concrete since it is a large volume mineral structure. In this study, ultra fine cement and silica fume as mineral additive were used together for binder design. In addition, micro fiber has been added to the binder systems produced in different proportions. The produced specimens were kept separately in water, in solutions containing 2% Na2SO4 and 2% MgSO4 by weight for 90 days. The compressive strength test was performed at 28th and 90th days on cured specimens. In addition to the compressive strength test, the solution samples were taken from the curing solutions every 10 days and the concentrations of sulfate ions were also examined in the solutions. According to the results, more strength loss was observed in the specimens cured in MgSO4 solution. In parallel to this result, both the concentrations of SO42-ions in the MgSO4 solution were lower than those in the NaSO4 solution and no significant decrease was observed in the compressive strength of the specimens cured in NaSO4 solution, because the fibers can compensate the internal stresses. This situation shows that especially the micro fiber additive can compensate the expansion that will occur as a result of ettlingite formation, and thus it can help the mechanical stability of the concrete.

The aim of this study was to obtain new electrochemically modified electrodes with graphene and Au, Pt, Ag particles considering graphite (GP) and glassy carbon (GC) substrate by applying the chronoamperometry technique in order to develop the detection protocol of tetracycline (TC) considered as emerging pollutant in water, using cyclic voltammetry (CV) technique. The graphite-based substrate used for Ag/ Au/ Pt electrodeposition led to the electrode compositions on which TC oxidation process was not diffusion-controlled and as consequence, TC detection failed. TC detection protocols were developed for all Ag/Au /Pt electrodeposited GC and GC-GP electrodes. Better limits of TC detection was achieved for Ag electrodeposited on GC-GP at the cathodic potential of 0.460 V/SCE.

The paper presents the influence of acid neutralization capacity in industrial waste samples as a decision indicator. For the analysis of the acid neutralization capacity, 6 samples of wastes from different sectors of activity were subjected. This method is applicable to determine the acid neutralization capacity of material. The acid neutralizing capacity (ANC) was evaluated with HCl 1 N by neutralizing the excess with NaOH 0.5 N after 15 min stirring. From the results obtained it is found that the acid neutralization capacity can provide essential information for the subsequent management of the waste.

Waste-to-energy projects can be classified as a complementary technology for energy recovery from non-recyclable municipal waste fractions and should therefore not compete with measures to reduce, reuse and recycle materials. The article presents the characterization of some trated municipal solid wastes as competitive raw materials for combustible materials obtaining. Samples with ligno-cellulosic and polymeric composition were analyzed, namely 3 samples of SRFs (solid recovered fuels) used as secondary raw material in cement plants, SRF1, SRF2, SRF3; a sample of RDF, consisting of household waste; a sample of fluff (homogeneous mixture of non-hazardous waste - selected, mechanically treated and dried) used as a secondary raw material in cement plants; 4 samples of municipal solid waste, fractions smaller than 100 mm, after a bio-drying process, with composition: paper and cardboard (70-80%), wood (6-15%), plastic (6-10%), glass and metal (3-14%), MBU1, MBU2, MBU3, MBU4. The waste samples were characterized in terms of technical and elementary characteristics and the ash (obtained by the sample incineration) behavior in the combustion process. The mineral matter was investigated by the X-ray fluorescence analytical technique using the Rigaku CG X-ray Spectrofluorimeter. The analysis of the indices used for the slagging and deposit formation risks evaluation shows that the analysed samples present an obvious risk of melt formation and deposits, due to a high content of base oxides and silicon oxide.

In this paper a comparison is made of the level of air pollution from two brick production lines that apply different technologies, one old and one new more efficient. The main pollutants emitted into the air from the baking of raw bricks in baking kilns are CO, SO2, NO2, HCl, HF and dust. Monitoring of air pollutants was performed with a Teso 350 flue gas analyzer – the automatic method. A Paul Gothe isokinetic sampler was used to take dust particles, HCl, and HF samples, and the analysis was performed in the laboratory using gravimetry and spectrophotometry as analytical techniques. The results of the tests performed showed a reduction in the level of pollution by applying BAT technologies by up to 90% for all monitored pollutants, compared to the pollution produced by an old, non-retechnologized line. At the same time, energy consumption is lower per unit of product, which results in a significant decrease in production costs.

The aim of this study was to develop two analytical methods for the determination of Cr6 + from fixed source emissions, such us the molecular absorption spectrophotometric method (UV-VIS) and the graphite furnace atomization absorption spectrometry method (GTAAS). The first stage in the development of analytical methods involves establishing the optimal operating conditions for, taking air samples, treating them for analysis and the proceeding for analysis, followed by validating the method by determining performance parameters. For both methods is high recommended, the use of isokinetic sampling with a sampling probe by heated glass, quartz or PTFE. Dust from the gaseous effluent is retained on the filter. Then, the gaseous effluent is passed through a series of absorbers containing a 0.1M Na OH absorbent solution. When the gaseous effluent has a strong acid character (high concentrations of SO2, NOx. HCl, HF, etc.) is recommended to use a 0.5M NaOH absorbent solution. The maintaining of the pH at values > 8.5 in the exposed absorbent solutions was one of the conditions of validity of the sampling. The limit of detection and the limit of quantification were concluded to be 12.38 µg / m3 and 40 µg / m3, respectively for the UV-VIS method and for the GTAAS method 0.12 µg / m3 and 0.54 µg / m3 respectively.

The sludge management resulting from the urban wastewater treatment plants, from the point of view of circular economy, follows its using as a fertilizer for agricultural lands, degraded lands, in horticulture and forestry. The aim of this paper is the proposing of an alternative way of using the sludge resulting from urban wastewater treatment plants in a sustainable way with a low impact on the environment. The experimental results showed the efficiency of using the stabilized sludge as fertilizer for naturally and anthropically degraded lands and cultivated with Salix sp. The use of stabilized sludge determined the improvement of the nutritional characteristics of the degraded lands, which allowed the growth, development and maintenance of the culture of Salix sp. Considering the characteristics of the cultures and the quantities of metals accumulated by Salix sp., it can be concluded that it has adapted to the environmental and the substrate conditions from the studied degraded lands. The results obtained on the two degraded lands indicate that Salix sp. can be used for its introduction in the economic circuit, both of the salty soils and of the slag and ash deposits.

The soil cover is subject to anthropogenic changes as well as other geoecosystems subjected to pressures due to sources. The results are recorded for the soil cover depending on the type of anthropogenic manifestations, intensity, nature and number of their manifestations. Moreover, the interferences with the natural landscapes intervene and from here appear the evaluation process difficulties. In most cases it is considered that the urban landscape is distinguished by a series of peculiarities regarding the quality of the urban hydrosphere, an atmosphere and the biosphere, as well as a series of changes in the pedosphere, as a result of land use. Notable for the soil cover, being particularly important is the soil cover the surface of the pedosphere. The complex of ecological parameters can provide important information on the flows and balance within the ecological system. The ecological importance of urban soils has long been underestimated. Urban soils were protected only as a support for construction. It was not until the early 1970s that the first approaches to the study and classification of urban soils were initiated. We can say that in 2020 the situation is completely different, in the sense that urban soils are studied and evaluated periodically in terms of quality.

The environment pollution is an important issue influencing on human health and environmental equilibrium. The range of pollutants is very wide due to the industrialization and population growth and the surfactants are one of the most common organic pollutants due to their extensive use and ubiquitous presence from industry to households. Their massive presence in the domestic and industrial wastewater could affect the Wastewater treatment plants by inhibit the activated sludge used in pollutants biodegradation treatment step. This paper aimed to study the inhibition effect of three classes of surfactants (nonionic, anionic and cationic) by measuring of the respiratory activity of microorganisms with the application of the Oxygen Uptake Rate (OUR) test. This study established that the surfactants can activate or inhibit microorganisms activity, depending on surfactant concentration.