Environmental tradeoffs in municipal wastewater treatment plant upgrade: a life cycle perspective

Optimization of indirect wastewater characterization using led spectrophotometry: a comparative analysis of regression, scaling, and dimensionality reduction methods

LED spectrophotometry is a robust technique for the indirect characterization of wastewater pollutant load through correlation modeling. To tackle this issue, a dataset with 1300 samples was collected, from both raw and treated wastewater from 45 wastewater treatment plants in Spain and Chile collected over 4 years. The type of regressor, scaling, and dimensionality reduction technique and nature of the data play crucial roles in the performance of the processing pipeline. Eighty-four pipelines were tested through exhaustive experimentation resulting from the combination of 7 regression techniques, 3 scaling methods, and 4 possible dimensional reductions. Those combinations were tested on the prediction of chemical oxygen demand (COD) and total suspended solids (TSS). Each pipeline underwent a tenfold cross-validation on 15 sub-datasets derived from the original dataset, accounting for variations in plants and wastewater types. The results point to the normalization of the data followed by a conversion through the PCA to finally apply a Random Forest Regressor as the combination which stood out These results highlight the importance of modeling strategies in wastewater management using techniques such as LED spectrophotometry.

Evaluating the environmental and economic performance of biological and advanced biological wastewater treatment plants by life cycle assessment and life cycle costing

The primary objective of this study is to assess and establish benchmarks for environmental and economic sustainability of biological and advanced biological wastewater treatment plants (WWTPs) with different treatment technologies and characteristics. Furthermore, the study aims to determine the beneficial role of WWTPs to reduction of eutrophication potential. Environmental and economic sustainability of ten municipal WWTPs was assessed using life cycle assessment (LCA) and life cycle costing (LCC). In the first section of the study, LCA was performed to determine the environmental performance of the WWTPs. Furthermore, net environmental benefit (NEB) approach was implemented to reveal the beneficial role of WWTPs to eutrophication potential. In the subsequent section, LCA-based LCC was conducted by integrating the results of LCA. The most significant environmental impact was determined as marine aquatic ecotoxicity, which is highly affected from the generation and transmission of electricity consumed in the WWTPs. Wastewater recovery and co-incineration of sewage sludge in cement kiln ensure significant environmental savings on ozone layer depletion, human toxicity, acidification, photochemical oxidation, and abiotic depletion (fossil fuel) potential. Considering NEB approach, the highest NEB values were found for the WWTPs with the higher organic load and nutrient concentration in the influent. The results of LCC in WWTPs varied between 0.21 and 0.53 €/m3. External (environmental) costs were evaluated higher than internal (operational) costs for all selected WWTPs. While eutrophication was the highest among environmental costs, electricity cost was the highest among operational costs for almost all WWTPs.

Trading-off greenhouse gas emissions and 741/2020 European Union water reuse legislation: An experimental MBR study

A trade-off between greenhouse emissions (direct and indirect) and operational costs in the water treatment sector is of great importance, although only few literature studies exist. The paper presents a comprehensive experimental study on a Membrane Bioreactor (MBR) pilot plant at the Water Resource Recovery Facility of Palermo University (Italy). The MBR pilot plant was aimed at reducing carbon footprint while producing water suitable for water reuse in agriculture. Multiple scenarios were assessed to unveil the best operational variables including the assessment of the reclaimed water quality index for water reuse. Results showed the lowest operational costs for the MBR of 5.05 € cent/m3 with Class B according to 741/2020 European legislation. Results revealed optimised values, in terms of airflow rate and backwash frequency, of 0.8 m3/m2/h and 12 times/h, respectively. The highest N2O emission was measured in correspondence of scenario S5 (airflow rate of 1.6 m3/m2/h) with 0.40 mg N2O-N/m2/h in agreement with previous literature studies. The obtained results could effectively address the operators to find a trade-off between operational costs and water quality.

Integrating life cycle assessment with quantitative microbial risk assessment for a holistic evaluation of sewage treatment plant

An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 kWh.day^-1) contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.

Sustainability assessment of retrofitting alternatives for large and old wastewater treatment plants in Seoul

Old wastewater treatment plants (WWTPs) must be upgraded to alleviate the problems associated with aging and reduce their total environmental impacts. To enhance the environmental sustainability in retrofitting large and old WWTPs, the decision-making process for selecting the most appropriate alternative is complicated. In this study, evaluation criteria were proposed to select the most sustainable alternatives for mid- to long-term retrofitting plans for a large WWTP with the treatment capacity of 1.6 M m³/d, which is initially built in 1987. An analytic hierarchy process was applied to estimate the weights of each criterion. Fourteen experts evaluated the relative importance of criteria through pairwise comparisons. In order to assess the current retrofitting opinions, three retrofitting alternatives were constructed: A focused on energy sufficiency; B expanded the bioreactor capacity and enhancement of the facility for incinerating the sludge leaving the anaerobic digestor; C emphasized the treatment of contaminants of emerging concerns (CECs). A achieved the highest score (0.623) owing to the environmental benefits associated with recycling and first flush stormwater treatment. C exhibited the second highest score (0.612) as the focus on CECs removal. B corresponded to the lowest sustainability (0.426), with the lowest scores pertaining to effective land use and first flush stormwater treatment.

Life Cycle Assessment and Its Application in Wastewater Treatment: A Brief Overview

This paper provides a brief review on wastewater treatment system and the application of life cycle assessment (LCA) for assessing its environmental performance. An extensive review regarding the geographical relevance of LCA for WWTPs, and the evaluation of sustainable wastewater treatment by LCA in both developed and developing countries are also discussed. The objective of the review is to identify knowledge gap, for the improvement of the LCA application and methodology to WWTPs. A total of 35 published articles related to wastewater treatment (WWT) and LCA from international scientific journals were studied thoroughly and summarised from 2006 to 2022. This review found that there is lack of studies concerning LCA of WWTPs that consider specific local criteria especially in the developing countries. Thus, it is important to: (1) assess the influence of seasonality (i.e., dry and wet seasons) on the environmental impact of WWT, (2) investigate environmental impacts from WWTPs in developing countries focusing on the site-specific inventory data, and (3) evaluate environmental sustainability of different processes for upgrading the wastewater treatment system. The environmental impact and cost assessment aspects are crucial for the sustainable development of WWTP. Therefore, environmental impacts must be thoroughly assessed to provide recommendation for future policy and for the water industry in determining environmental trade-offs toward sustainable development.

Distribution characteristics of phosphorus-containing substances in a long running aerobic granular sludge-membrane bioreactor with no sludge discharge

This work aimed at revealing the distribution characteristics of phosphorus (P) containing substances in an aerobic granular sludge-membrane bioreactor (AGS-MBR). During the long running period (180 days) with no sludge discharge, AGS was successfully cultivated on day 20, and the system performed well in removing organic pollutants and total nitrogen (TN). However, the removal of total P (TP) showed a fluctuant tendency, and P was found to distribute in all the phases of the system. In the intracellular phase, it occupied the largest ratio all through the period. In AGS, inorganic P (IP) was measured to be about 74.4-77.8% of TP, with non-apatite IP (NAIP) composing 57.5-69.6%, while in organic P (OP), the ratio of monoester and diester phosphate was in the range of 19-26.9% and 12-13.5%, respectively. The presence of highly releasable and bioavailable P (NAIP + OP) in AGS implied that it might be a potential P resource for utilization.