Environmental Impact Of Wastewater Research Articles

Integrated Exposure and Algal Ecotoxicological Assessments of Effluents from Secondary and Advanced-Tertiary Wastewater-Treatment Plants.

The great concern over the environmental impact of wastewaters has led to the designing of advanced treatment processes to upgrade conventional treatment plants and achieve a significant reduction of contaminants in receiving waters. In the present study we combined chemical and ecotoxicological analyses, aiming to evaluate the reduction of toxicity effects associated with the removal of micropollutants and to define the contribution of the detected compounds to the overall toxicity of the mixtures in a series of wastewater effluents collected from a secondary treatment (OUT 2) and from a tertiary activated carbon treatment (OUT 3) plant. The target compounds were selected after a screening procedure among pharmaceuticals, musk fragrances, and trace metals. The classical algal growth inhibition test was conducted on the original effluent samples and on different fractions obtained by solid-phase extraction (SPE) treatment. A good accordance was found between the removal of toxicity (30%-80%) and organic compounds (70%-80%) after the tertiary treatment, suggesting its high efficiency to improve the wastewater quality. The discrepancy between the contribution to the overall toxicity of the nonadsorbable compounds (i.e., inorganic or very polar organic compounds) as experimentally measured by the SPE bioassays (18%-76%) and calculated by the concentration addition approach (>97%) could be mitigated by including the bioavailability correction in metal-toxicity modeling of wastewater mixtures. For the organic compounds, the toxic equivalency method enabled us to quantify the portion of toxicity explained by the detected chemicals in both OUT 2 (82%-104%) and OUT 3 (5%-57%), validating the selection of the target molecules. The applied integrating approach could be implemented by the inclusion of both additional target chemicals and toxicity endpoints. Environ Toxicol Chem 2022;41:2404-2419. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Life cycle assessment for the upgrade of a wastewater treatment plant from secondary to tertiary treatment

A life cycle assessment (LCA) was applied in a recent project of upgrading Tazmant wastewater treatment plant in Egypt from secondary to tertiary treatment, taking into the consideration construction phase of the project as well as operation phase of the tertiary treatment. The LCA studies were carried out using CML 2001 impact assessment methodology. It was revealed that the upgrading of Tazmant wastewater treatment plant reduces the environmental impact by 43% from the acidification potential, 60% from the eutrophication potential, 62.5% the ozone layer depletion potential, 42% of abiotic depletion elements point, and 62.5% of photochemical ozone creation potential viewpoints. In addition, the effect of toxicity potential resulting from the operation of tertiary treatment alone amounts to only 20% of that resulting from secondary treatment, which reflects the positive environmental impact of wastewater recycling in addition to the water-saving gained from water reuse.

Avaliação de Impacto Ambiental de Descargas de Águas Residuais Usando Uma Metodologia Geoestatística

The main purpose of this study was to analyze the applicability of geostatistical modeling to evaluate the environmental impact of wastewaters from sea outfalls. The set of data was obtained in a monitoring campaign of the sea outfall of S. Jacinto., in the region of Aveiro on the West coast of Portugal. The data were collected close to the discharge using an Autonomous Underwater Vehicle (AUV — Veiculo Submarino Autonomo). Matheron’s classical estimator was used to calculate the experimental semivariogram, and this was adjusted to the spherical, exponential and Gaussian theoretical models. The cross-validation technique suggested the most appropriate model and ordinary kriging was used to obtain the estimates of salinity at non-sampled points. The map estimated by kriging clearly shows the plume dispersion in the area studied, indicating that the effluent did not reach the closest beaches. This study suggests that a strategy for optimized AUV from the standpoint of geostatistics may supply better estimates compared to other interpolation methods that do not supply the errors associated with the estimates, for instance Inverse Distances Weighting (IDW), Global Polynomial, Local Polynomial, and others. Besides, since accurate measures for plume dilution are rare, these studies may be very useful in future to validate dispersion models

2 褐炭利用において発生する排水の環境負荷低減(改質,処理,クリーン化)

2 褐炭利用において発生する排水の環境負荷低減(改質,処理,クリーン化)

Wastewater Reuse in Valsequillo Agricultural Area, Mexico: Environmental Impact on Groundwater

Wastewater and groundwater has been used for irrigation in the Valsequillo District, east central Mexico, for nearly 50 years. The environmental impact of wastewater on groundwater in the unconfined shallow aquifer is evaluated by means of hydrogeological, microbiological, hydrogeochemical and isotopic evidences. The shallow aquifer consists of upper Tertiary volcano-sedimentary rocks with a calcite-rich matrix. Groundwater from wells near the wastewater canal had similar total coliforms concentrations as the wastewater (∼100 MPN 100 mL-1). The hydraulic head in near-canal wells had a recovery of 10 m until 1983, indicating shallow recharge from wastewater. A bicarbonate vs. calcium plot shows a well-defined mixing process between wastewater and unaffected groundwater. Stable isotopic data (δD and δ18O) show characteristic signatures for wastewater and non-impacted groundwater, and define a mixing line between those end-members and groundwater affected by wastewater infiltration. Tritium data indicate that non-impacted groundwater is ‘pre-atomic hydrogen bomb’ (>50 yr), whereas the wastewater has a ‘younger’ signature. Tritium data from wells inside the district clearly indicate a mixing process between waste and groundwater. These results demonstrate the interaction and hydrochemical processes between wastewater and shallow groundwater at the site.

LOW - POLLUTION BLEACHING OF PULP

The paper presents the investigations on bleaching of spruce kraft pulp with oxygen and peroxide according to (OP)-Q- (EOP)-P sequence: (OP) oxygen-peroxide stage; Q chelating stage; (EOP) alkali extraction with oxygen and peroxide stage; P peroxide stage). The pulp brightness and properties were found highly dependent on unbleached pulp Kappa number and on residual lignin content after (EOP) stage. Also, the final P stage conditions strongly influence the bleaching results. In order to achieve a satisfactory pulp brightness (84-86 % ISO), it is necessary to split the chemical charge in the P stage, so that it could be replaced with P-P or better P-P-P, without a washing interstage. The above-mentioned bleaching sequence allows the improvement of water balance, and thus bringing environmental benefits, both in terms of water conservation and by decreasing the environmental impact of wastewaters.