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•Lab-scaled photocatalyst (TiO2) was prepared by the solution combustion method.•Synthesize photocatalyst characterized by FESEM, XRD and XPS.•BOD5/COD (0.59±0.089) and BOD5/TOC ...(1.74±0.03) were improved by photocatalytic degradation.•Maximum removal efficiency obtained was 98.43±1.31% through integrated system.•The performance of PBBR was analyzed in terms of % REP, PLR and % ECPR.
Integratingphotocatalysisand biodegradation has shown great potential in wastewater treatment technology. In this study, the degradation of p-cresol in water has been investigated through an integrated system comprising of photocatalytic and packed bed biofilm reactor (PBBR). In the photocatalytic reactor, the biodegradability index (BOD5/COD, BOD5/TOC) of the p-cresol solution was first shown to increase (from 0.098±0.023 to 0.59±0.089 for BOD5/COD and from 0.27±0.030 to 1.74±0.03 for BOD5/TOC). The pseudo-first-order rate constant (kap) was found to be 0.011 min−1. The % removal of the integrated system was found to be 98.43±1.31% at an initial concentration of 700 mg L-1 and residence time of 120 h, which was significantly higher than the PBBR operated alone (34.82±2.62%) under optimized conditions (pH 7.0 and T = 32±2 °C). Using an integrated approach, the efficient removal of p-cresol opens novel future perspectives for catalytic degradation using chemical oxidation.
In many coastal cities around the world, continuing water degradation threatens the living environment of humans and aquatic organisms. To assess and control the water pollution situation, this study ...estimated the Biochemical Oxygen Demand (BOD) concentration of Hong Kong's marine waters using remote sensing and an improved machine learning (ML) method. The scheme was derived from four ML algorithms (RBF, SVR, RF, XGB) and calibrated using a large amount (N > 1000) of in-situ BOD5 data. Based on labeled datasets with different preprocessing, i.e., the original BOD5, the log10(BOD5), and label distribution smoothing (LDS), three types of models were trained and evaluated. The results highlight the superior potential of the LDS-based model to improve BOD5 estimate by dealing with imbalanced training dataset. Additionally, XGB and RF outperformed RBF and SVR when the model was developed using log10(BOD5) or LDS(BOD5). Over two decades, the BOD5 concentration of Hong Kong marine waters in the autumn (Sep. to Nov.) shows a downward trend, with significant decreases in Deep Bay, Western Buffer, Victoria Harbour, Eastern Buffer, Junk Bay, Port Shelter, and the Tolo Harbour and Channel. Principal component analysis revealed that nutrient levels emerged as the predominant factor in Victoria Harbour and the interior of Deep Bay, while chlorophyll-related and physical parameters were dominant in Southern, Mirs Bay, Northwestern, and the outlet of Deep Bay. LDS provides a new perspective to improve ML-based water quality estimation by alleviating the imbalance in the labeled dataset. Overall, the remotely sensed BOD5 can offer insight into the spatial-temporal distribution of organic matter in Hong Kong coastal waters and valuable guidance for the pollution control.
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•Imbalanced datasets bias the supervised machine learning (SML) derived BOD5.•An optimized SML approach based on label distribution smoothing is proposed.•A 20-year remotely sensed BOD5 is conducted across Hong Kong marine waters.•Downward trends of BOD5 cover almost all of Hong Kong's marine waters.
The aim of this study was to determine the biodegradability of organic and biogenic contaminants in wastewater flowing into biological reactors in the treatment plant in Nowy Targ. The research ...period covered the years 2016 and 2017, when 87 samples of raw wastewater and 87 samples of wastewater after mechanical treatment were collected and subjected to physico-chemical analysis. In both types of wastewater, the size of the following indicators was analyzed: BOD5, COD, total kjeldahl nitrogen (TN) and total phosphorus (TP). The study verified the amount of pollutants in the raw wastewater in order to determine whether they are household wastewater. In the next stage of the analysis, the characteristic values of the analyzed indicators in wastewater after the mechanical treatment process were determined in order to indicate mutual dependences of organic and biogenic indicators. Based on the analysis, it was found that wastewater after mechanical treatment (in the case of its susceptibility to biological decomposition processes of organic pollutants) has an unfavorable COD/BOD5 ratio. With regard to the susceptibility of wastewater to nitrification, denitrification and dephosphatation processes, in the majority of cases, wastewater is susceptible to these processes. It is recommended to apply an additional source of organic carbon to wastewater prior to biological treatment in order to improve the biodegradation of the analyzed pollutants.
Pangandaran Regency is famous for salted fish, both for consumption by the surrounding community and for souvenirs. In the salty fish production process, of course, a lot of liquid waste is produced. ...The method of preparation, washing and soaking are the three stages that make the most wastewater in salting fish. Salted fish processing liquid waste is an organic waste that can be reduced its pollution parameters through ozonation technology. This study aims to study the effect of effluent pH and ozonation time on the level of degradation of effluent pollution parameters, such as: TSS, TDS, COD, BOD5, and salinity. From the analysis results, it is known that the process of flowing ozone for 80 minutes at pH 9 can reduce TSS, TDS, and salinity to the maximum, by 86.23%, 62.42%, and 61.38%, respectively. The most reductions in COD and BOD5 were achieved after giving ozone for 20 minutes at pH 10, as much as 52.20% and 54.69%, respectively. It is known that the TSS and TDS of wastewater that has been given ozone may be below the quality standard set by the Minister of the Environment, but this does not yet apply to levels of COD and BOD5. Additional processing is required so that the COD and BOD5 values can be below the quality standards recommended by the Minister of the Environment.
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•Calcined CaFe–LDH based hybrid photocatalyst was successfully prepared.•1.0 g CuCr2O4@CaFe–LDO achieved 66% COD removal after 300 mins in the dark.•CuCr2O4@CaFe–LDO/K2S2O8/sunlight ...system resulted in ~99% and 98.3% COD and colour removal.•Seven phenolic compounds were found in the crude olive mill wastewater and were completely degraded after 300 min.•The catalyst was recovered easily with an external magnet from the bulk solution after the reaction.
Wastewater from the olive mill constitutes a serious environmental concern, as it is characterized by a high inorganic and organic load. Here, a hybrid photocatalyst based on calcined Ca-Fe–LDH was successfully synthesized for the degradation of phenolic compounds and the removal of chemical oxygen demand (COD) from the high-strength olive mill wastewater (OMW). The catalyst (CuCr2O4@CaFe–LDO) displayed a stable ~4.48 µA cm−2 photocurrent response, a 2.56 eV bandgap and a wide variety of pores with an average size of 12.51 nm. 1.0 g CuCr2O4@CaFe–LDO achieved 66% COD removal after 300 mins without an oxidant in the dark, while after 180 mins of reaction, CuCr2O4@CaFe–LDO/K2S2O8/sunlight system resulted in ~99% and 98.3% COD and colour removal. Seven phenolic compounds were found in the crude OMW, with hydroxytyrosol (76.84%) and tyrosol (15.14%) being the main ones. The final pH of the sample treated increased from 4.3 to 7.3, which confirmed the degradation of phenolics and fatty acids in the OMW. OH, SO4−, h+ and O2− contributed notably to the degradation of polyphenols and the spent catalyst was easily and rapidly recovered from the bulk solution due to its saturation magnetization of 54.7 emu g−1.
•A multi-objective target was obtained by Fe(II)/PAA coupling UF for secondary effluent treatment.•Fe(II)/PAA could reduce UF fouling resistance by 90.2%.•BOD5 content and C/N ratio of UF permeate ...was greatly improved.•Fe(II)/PAA could effectively remove phosphorus by the in-situ generated Fe(Ⅲ).
Ultrafiltration (UF) is a technology commonly used to treat secondary effluents in wastewater reuse; however, it faces two main challenges: 1) membrane fouling and 2) inadequate nitrogen (N), phosphorus (P), and organic micropollutants (OMPs) removal. To address these two issues, in this study, we applied peracetic acid (PAA), Fe(VI)/PAA, and Fe(II)/PAA as UF pretreatments. The results showed that the most effective pretreatment was Fe(II)/200 μM PAA, which reduced the total fouling resistance by 90.2%. In comparison, the reduction was only 29.7% with 200 μM PAA alone and 64.3% with Fe(VI)/200 μM PAA. Fe(II)/200 μM PAA could effectively remove fluorescent components and hydrophobic organics in effluent organic matter (EfOM), and enhance the repulsive force between foulants and membrane (according to XDLVO analysis), and consequently, mitigate pore blocking and delay cake layer formation. Regarding pollutant removal, Fe(II)/200 μM PAA effectively degraded OMPs (>85%) and improved P removal by 58.2% via in-situ Fe(Ⅲ) co-precipitation. The quencher and probe experiments indicated that FeIVO2+, •OH, and CH3C(O)OO•/CH3C(O)O• all played important roles in micropollutant degradation with Fe(II)/PAA. Interestingly, PAA oxidation produced highly biodegradable products such as acetic acid, which significantly elevated the BOD5 level and increased the BOD5/total nitrogen (BOD5/TN) ratio from 0.8 to 8.6, benefiting N removal with subsequent denitrification. Overall, the Fe(II)/PAA process exhibits great potential as a UF pretreatment to control membrane fouling and improve water quality during secondary effluent treatment.
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The accelerated growth of the population in recent years presents, as a great consequence, a significant increase in wastewater, which, on many occasions, is not discharged properly. This work aims ...to design a sewerage and wastewater treatment system in Las Mercedes commune in southern Ecuador based on geological, topographic, hydrological, geochemical and demographic parameters. All this focused on reducing pollution and complying with current national and international regulations, meeting the needs of the rural population studied. The methodology used consists of four phases: i) collection, inventory and processing of the base information ii) design of the sewerage system, ii) design of a wastewater treatment system and iv) environmental impact assessment and referential budget. The sewerage system consists of 3.2 km long PVC pipes that transport wastewater to a purification system of water pretreatment and facultative and maturation ponds. The designed system complies with a total purification of 636.27 MPN/100 ml of faecal coliforms (99.994%) and 35.30 mg/l of BOD5 (88%). The proposed design contributes to wastewater management and environmental education research, defining a combined model of a sewerage system with stabilisation ponds replicable in communities with similar conditions.
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•Effluent nitrogen control strategy was validated in a continuous flow SNADCO process.•Stable operation was feasible at influent ammonium concentration of 500–1500 mg/L.•Total ...nitrogen removal efficiency was high as 87.3–91.2%.•COD and BOD5removal efficiencies were 80.8–81.2% and 91.1–98.9%.•Functional groups of bacteria were compered by giving activity and relative abundance.
A simultaneous partial nitritation, anammox, denitrification, and COD oxidation (SNADCO) process was used to evaluate the nitrogen and biodegradable organic matter removal of swine manure digestate based on a nitrite limitation and ammonium surplus strategy. As influent ammonium concentration increased from 500 mg/L to 2100 mg/L, the 5 day biochemical oxygen demand (BOD5) maintained at a high removal efficiency of 95.4%. However, nitrogen removal efficiency (NRE) decreased from 90.9% to 68.2% due to the inhibition of AnAOB caused by an ammonium concentration of 2100 mg/L. The contribution of AnAOB to nitrogen removal was 75.6–86.5%, while that of denitrifying bacteria was 4.6–7.0%. In the case of COD removal, the contributions were from ordinary heterotrophic organisms and denitrifying bacteria, at 27.1–64.9% and 11.2–22.1%, respectively. The results of specific bacteria activity tests and microbial analysis showed that a highly efficient synergism between functional microorganisms is essential for the stability of the SNADCO process.
Wastewater treatment is a process used in several countries, particularly in Algeria. A study on Earth for one month was carried out at the sewage plant of the Sebdou textile complex, Tlemcen, ...north-west of Algeria. Regular samples gave average values at the outlet such that the water temperature is 22 ° C, the ph 7.43, the biochemical oxygen demand BOD5 is 36.5 mg / l, the chemical oxygen demand COD vary between 100 and 200 mg / l at the exit of the WWTP mg / l and finally suspended solids SS is of the order of 36.2 mg / l. All these values conform with the standards and therefore the treatment plant operates within Algerian standards.
In this work, we present results of the first long-term oceanographic study of the mussel farm area in the brackish oligotrophic coastal waters off Sevastopol (Crimea, Black Sea). The long-term ...seasonal and annual variations of the thermohaline and main hydrochemical characteristics, their trends and probability distributions are reported. The significant trends are related to the regional climate change and phytoplankton activity. The increased nitrate concentration in the mussel farm surface water as compared with the bottom water and background station surface water is explained by the nitrification in the mussel bed. The obtained trophic index (TRIX) values allow classifying the mussel farm area as the low-trophic region. The area under study is shown to be currently suitable in all parameters for the development of bivalve farming, but the negative trend of the silicate concentration observed in this work may lead in the future to the phytoplankton depletion and to disastrous consequences for the bivalve aquaculture in the southwest of Crimea.
•The first long-term oceanographic study of a mussel farm area is presented.•Many oceanological parameters under study demonstrate significant trends.•The trends are attributed to the regional climate change and phytoplankton activity.•The negative silicate trend is coupled to the long-term phytoplankton depletion.•The mussel farm in the brackish oligotrophic water affects little the environment.
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