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Assessment of the reliability of the operation of a sewage treatment plant using Monte Carlo simulation

Migdał Karolina, Operacz Agnieszka, Vaskina Iryna, Śliz Paulina, Tavares Jorge, Almeida Adelaide, Migdał Michał

Journal of Water and Land Development

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2022

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Special Issue

80--90

EN

The aim of the study was to model the operation of a wastewater treatment plant using the Monte Carlo method and selected probability distributions of random variables. Pollutant indices in treated wastewater were analysed, such as: biological oxygen demand (BOD5), chemical oxygen demand (CODCr), total suspended solids (TSS), total nitrogen (Ntot), total phosphorus (Ptot). The preliminary analysis of pollution indicators series included the: calculation of descriptive statistics and assessment of biological degradability of wastewater. The consistency of the theoretical distributions with the empirical ones was assessed using Anderson-Darling statistics. The best-fitting statistical distributions were selected using the percent bias criterion. Based on the calculations performed, it was found that the analysed indicators of pollution in treated wastewater were characterised by an average variability of composition for BOD5, CODCr and TSS, and a high variability of composition for Ntot and Ptot. The best fitted distribution was log-normal for BOD5, TSS, Ntot and Ptot and general extreme values for CODCr. The simulation carried out using the Monte-Carlo method confirmed that there may be problems associated with the reduction of nutrients (Ntot and Ptot) the analysed wastewater treatment plant. Results of values obtained of the risk values of negative control of wastewater treatment plant operation for biogenic compounds, different from 1, indicate that the number of exceedances at the outflow may be higher than the acceptable one.

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Sensory Quality of Portuguese Natural Mineral Waters: Correlation with Chemical Composition

Sozo Jenny Sumara, Pardal Ana, Carvalho Maria João, Almeida Adelaide, Chaves Humberto, Carvalho Maria de Fátima

Ecological Engineering & Environmental Technology

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2021

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Vol. 22, iss. 3

129--141

EN

Portugal is one of the richest countries in terms of the variety of natural mineral waters in relation to the territorial size. The aim of this work was to characterize the sensory features of eleven Portuguese natural mineral waters and correlate those with their chemical characteristics. The study of the Piper diagram concluded that the vast majority of these waters have low or very low mineralization content, with total mineralization values not more than 500 mg/L, predominantly sodium bicarbonate or mixed sodium. The sensory analysis was carried out by 10 trained panelists according to ISO 8586:2012 and showed that the tasters were able to distinguish the sensory attributes of the waters, and thus it was possible to establish some correlation between the physical-chemical and sensory parameters. With Principal Component Analysis (PCA), it was possible to explain the percentage of variance between the main chemical components of the studied waters and its sensory characteristics. A significant positive correlation of Total Dissolved Solids (TDS) with HCO3-(0.97), Ca2+ (0.93) and Mg2+ (0.91) was shown, as well as the pH of the natural mineral waters with the salty (0.71) and the sweet (0.69) taste. The sweetest waters were Monchique Chic (3.4) and Monchique (3.3) and the least sweet was Luso. The most acidic were Vitalis (3.4) and Luso (3.3) and the least acidic ones were Monchique Chic (1.9) and Vimeiro Original (1.8). In terms of the salty taste, the most salty samples were Monchique (4.2) with significant differences between all the other samples, and the least salty one was Salutis (1.8). The bitter waters were Monchique Chic (3.5) and Vimeiro Lisa (3.4) and Vitalis was the least bitter (2.3). The water with the highest score in mineral flavor was Vimeiro Original (4.9) and the lowest one was Salutis (2.7).

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Study on the Application of Floating Beds of Macrophites (Vetiveria zizanioides and Phragmites australis), in Pilot Scale, for the Removal of Heavy Metals from Água Forte Stream (Alentejo-Portugal)

Borralho Teresa, Gago David, Almeida Adelaide

Journal of Ecological Engineering

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2020

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Vol. 21, nr 3

153--163

EN

The surrounding area of the Roxo stream sub-basin (basin of the Sado River, Portugal) has completely sterile sections, jeopardizing the productivity of the agricultural activities practiced there. This may be due to the inflow of the Água Forte stream, which has characteristics of Acid Mining Drainage (AMD). The objective of this study was to test the efficiency of heavy metal removal from the Água Forte stream using the macrophyte floating bed technology (Vetiveria zizanioides and Phragmites australis) in a pilot plant, monitoring and evaluating the water quality and performance of macrophytes. Two experiments were carried out in 2019 over 6 months (January to June). Both experiments were performed in polyvinyl chloride (PVC) tanks with the nominal capacity of 1 m3 each. The tanks were filled with about 0.8 m3 of water coming from the Água Forte stream, which was renewed monthly. The floating beds consisted in a high-density polyethylene floating system and an organic plant support mat filled with a plant density of 285 plants m-2. The heavy metal removal rates obtained from the Vetiveria zizanioides and Phragmites australis floating bed were Fe = 40%; Zn = 33%; Cu = 23%; Mn = 14% and Fe = 27%; Zn = 19%; Mn = 17%; Cu = 14%; respectively. The order of heavy metals accumulation in Vetiveria zizanioides and Phragmites australis in plant biomass was Fe > Zn > Cu > Mn and Fe > Zn > Mn > Cu, respectively. The growth of Vetiveria zizanioides and Phragmites australis in leaf biomass was 7.1 ± 0.3 cm/month and 2.5 ± 0.0 cm/month and in root biomass 3.8 ± 0.1 cm/month and 4.1 ± 0.1 cm/month, respectively. The growth of macrophytes showed the ability to survive in the AMD-containing waters without severe damage in their external and anatomical morphology, although their growth suffered inhibition. The results suggest that the floating bed technology may be an environmentally sustainable alternative, allowing long-term heavy metal removal.

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Manual Treatment of Urban Wastewater by Chemical Precipitation for Production of Hydroponic Nutrient Solutions

Correia Tânia, Regato Mariana, Almeida Adelaide, Santos Teresa, Amaral Leonor, Carvalho Fátima

Journal of Ecological Engineering

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2020

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Vol. 21, nr 3

143--152

EN

An urban wastewater treatment system was developed in Portugal for posterior in situ feasibility testing at the Bulgarian Antarctic Base, using its domestic wastewater. The aim of this system was to develop a low cost, integrated approach for wastewater treatment and production of nutrient solutions (NS) for hydroponic cultivation of lettuce (Lactuca sativa var. crispa) in Antarctic stations, or any other place where the lack of resources and logistical hardships make the wastewater treatment and reuse impractical. The wastewater treatment system consisted in manual agitation lime chemical precipitation (LCPm) and effluent natural neutralization (NN) by atmospheric CO2 carbonation reactions (with and without air injection). The resulting effluent/NS had macronutrient values (nitrogen and phosphorous) for the hydroponic cultivation of lettuce below the values of commercial NS and a high pH (pH ≈ 8). The treatment achieved a total coliform removal rate of 100%. Before the LCPm treatment system development, several lime-based reagents were tested under different reaction pH and using mechanical agitation, to access their organic matter removal efficiency, as chemical oxygen demand (COD). The best COD removal results obtained were: commercial Ca(OH)2 (pH 11.5 – 89%), reagent grade Ca(OH)2 (pH 11.5 – 79%) and CaO (pH 12.0 – 64%).