Impact of paint shop decanter effluents on biological treatability of automotive industry wastewater

A three-year study on the treatment of domestic-industrial mixed wastewater using a full-scale hybrid constructed wetland

Three full-scale constructed wetlands (CWs), namely vertical flow (VFCW), surface flow (SFCW), and horizontal flow (HFCW) systems, were combined in a series process to form a hybrid CW, which was used for the treatment performance of domestic-industrial mixed wastewater and investigated over a three-year period. The hybrid CW demonstrated that it is effective and stable during the long-term treatment of high-loading mixed wastewater under different operation years, season changes, and technology processes, with the average removal efficiencies of suspended solids, chemical oxygen demand, biological oxygen demand, total nitrogen, ammonia nitrogen, nitrate nitrogen, and total phosphorous being 84, 40, 54, 54, 70, 40, and 46%, respectively. The effluent quality of the hybrid CW reached the highest discharge standard for wastewater treatment plants. First, a variety of pollutants from the mixed wastewater were effectively removed in the subsurface processes (VFCW and HFCW) via substrate adsorption and degradation of the attached biofilm. The higher dissolved oxygen content and oxygen transfer capacity values in the VFCW were favourable for the occurrence of aerobic pathways (such as nitrification and inorganic phosphorus oxidation). In addition, with the large consumption of oxygen in the previous process, the oxygen-enriching capacity of the SFCW processes, provided aerobic potential for the next stage. In particular, the plant debris in the SFCW temporarily increased the organics and suspended solids, further increasing the C/N ratio, which was beneficial for denitrification as the main nitrogen removal pathway in the HFCW.

Physicochemical analysis of wastewater generated from a coating industry in Mauritius

The coating industry is one of the most important consumers of water and chemicals and consequently is a major water polluter in Mauritius. The focus of this study was to characterise wastewater generated by a coating industry in Mauritius. The objectives were to develop a wastewater sampling strategy and to analyse the pollutant parameters as per Mauritian regulations. The wastewater samples were analysed for physicochemical properties and metal abundances over a period of 6 months. The physicochemical parameters analysed were pH, electrical conductivity (EC), true colour, total suspended solids (TSS), biological oxygen demand (BOD₅), chemical oxygen demand (COD), nitrate, phosphate, sulphate and free chlorine. The wastewater samples were also analysed for metal ions such as sodium, potassium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel and zinc. The results of the physicochemical parameters indicated the presence of biologically resistant organic matters in all the wastewater samples with elevated values of BOD₅ and COD, and low biodegradability index, respectively. The coating industry wastewater samples were acidic and saline in nature. Moreover, they presented high concentrations of TSS, free chlorine and sodium ions compared to standard limits promulgated by the Mauritian Government. Spearman's rank correlation matrix with non-linear regression analysis showed significant associations among the measured parameters which were found to have a common origin in the coating industry wastewater. This research will be useful for regular monitoring and setting up an adequate coating industry wastewater treatment for the potential reuse in production processes in Mauritius.

Co-metabolism of nonylphenol ethoxylate in sequencing batch reactor under aerobic conditions

The study evaluated the co-metabolism of nonylphenol polyethoxylate (NPEO) within a main substrate stream subjected to biodegradation in an activated sludge system. Peptone mixture simulating sewage was selected as the synthetic substrate. As a novel approach, the NPEO concentration was magnified to match the COD level of the peptone mixture, so that co-metabolism could be evaluated by respirometry and modeling. A sequencing batch reactor (SBR) set-up at high sludge age to also allow nitrification was operated for this purpose. A long acclimation phase was necessary to start NPEO biodegradation, which was completed with 15% residual by-products. Modeling of respirometric data could identify COD fractions of NPEO with corresponding process kinetics for the first time, where the biodegradation of by-products could be interpreted numerically as a hydrolysis mechanism. Nonylphenol diethoxylate (NP2EO) was observed as the major by-product affecting the biodegradation of NPEO, because NPEO and NP2EO accounted for 60 to 70% of the total soluble COD in the solution during the course of biological reactions. The co-metabolism characteristics basically defined NPEO as a substrate, with no appreciable inhibitory action on the microbial culture both in terms of heterotrophic and autotrophic activities.

Sustainable treatment of paint industry wastewater: Current techniques and challenges

Paint manufacturing industries produce wastewater containing high chemical oxygen demand and turbidity, besides organic matter, suspended solids, and heavy metals that cause enormous environmental damages. Safely treating this wastewater before being disposed to the natural water sources is essential for attaining the UN SDGs, particularly Goal 14: Life under water. Besides being efficient, wastewater treatment techniques must be sustainable - environmentally, economically, and ethically. While a few papers have reviewed specific treatment methods for certain pollutants, such as heavy metals, oils, and azo dyes from industrial wastewater, a comprehensive review of various treatment methods for all the pollutants of a particular industrial wastewater - paint industry - is lacking. This paper reviews the current treatment methods used for treating paint industry wastewater including the physicochemical, biological, and chemical treatment techniques. The physicochemical techniques produce large amount of sludge making it difficult for disposal while biological treatment techniques are difficult to maintain because of the uncertainties in the chemical compositions of the paint wastewater. Advanced oxidation processes are emerging as preferred methods among the chemical methods for reducing the toxicity of the various components of the paint wastewater with reduced sludge quantity. The review of various emerging techniques of paint industry wastewater treatments in this paper points to the need for paying greater attention to combining the oxidation and biological processes as they are emerging as sustainable methods for effective reduction of toxicity in paint wastewater while also reducing the sludge management challenges.

A novel pilot-scale installation integrated of improved sieve-tray tower and wet electrostatic precipitator for paint mist removal

In order to overcome the problem of decrease of the spraying exhausts purification efficiency caused by the paint mist, the installation combining of the improved sieve-tray tower and the wet electrostatic precipitator (WEP) was used for the treatment of the pilot-scale 1,000 m³ paint waste gas. The characteristics of paint mist were investigated, showing that the size distribution of oil-based paint mist located in the range of 5.4-43.4 μm with an approximate symmetrical distribution under the pressure of 0.4 MPa. The size of paint mist less than 10 μm accounted for ~50% in quantity. It was revealed that the integrated setup was able to remove the concentration of oil-based paint mist with ~98% removal efficiency, in which the improved sieve-tray tower contributed ~94% particles removal. The soluble volatile organic pollutants (VOCs) of spraying exhaust gas were also captured by sieve-tray tower, promoting VOCs removal. At last, the feasibility of integrated setup used in paint mist removal was analyzed, including the secondary pollutants treatment. The results exhibited the setup has the potential for industrial applications.Implications: Fabricating a pilot-scale installation integrated of the improved sieve-tray tower and wet electrostatic precipitator to remove spraying exhaust gas in the furniture factory efficiently. This tech meets China's VOC emission policy.

Detection, provenance and associated environmental risks of water quality pollutants during anomaly events in River Atoyac, Central Mexico: A real-time monitoring approach

River Atoyac is considered to be one of the most polluted rivers in Mexico due to the discharges of untreated or partially treated wastewater from industrial and municipal activities. In order to improve the river water quality, it is obligatory to identify the possible contaminant sources for upholding a well-balanced ecosystem. Henceforth, the present study incorporates the application of a continuous real-time monitoring system to identify the provenance of pollutants of the river mainly from anomaly events. Four monitoring stations were installed all along the River Atoyac in the State of Puebla, Central Mexico. The real-time monitoring systems have an ability to measure various water quality parameters for every 15 minutes such as Temperature (T), pH, Conductivity (EC), turbidity (TURB), Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP) and Spectral Absorption Coefficient (SAC). In total, eight water samples of anomaly events (i.e.) 2 per monitoring station during rainy (August-September) and winter seasons (November-December), that were detected using the parameters previously mentioned were procured and also analyzed in the laboratory for evaluating almost 54 physicochemical, inorganic and organic characteristics. Statistical results of factorial analysis explained that 30% of the total variance corresponded to textile effluents, 23% related to discharges produced by automobile and petrochemical industries, and 18% of the total variance defined the agricultural activities. Additionally, indices like Overall Index Pollution, Heavy Metal Evaluation Index, Screening Quick Reference Table and Molecular ratios of hydrocarbons for PAH sources was also calculated to estimate the grade of pollution and associated ecotoxicological risks. The present study also enlightens the fact that the assessed results will definitely provide valuable information for the management of river water quality by developing stringent public policies by governmental agencies for the sustainable conservation of Atoyac River.

A comparative study of anaerobic fixed film baffled reactor and up-flow anaerobic fixed film fixed bed reactor for biological removal of diethyl phthalate from wastewater: a performance, kinetic, biogas, and metabolic pathway study

BACKGROUND

Phthalic acid esters, including diethyl phthalate (DEP), which are considered as top-priority and hazardous pollutants, have received significant attention over the last decades. It is vital for industries to select the best treatment technology, especially when the DEP concentration in wastewater is high. Meanwhile, anaerobic biofilm-based reactors are considered as a promising option. Therefore, in the present study, for the biological removal of DEP from synthetic wastewater, two different anaerobic biofilm-based reactors, including anaerobic fixed film baffled reactor (AnFFBR) and up-flow anaerobic fixed film fixed bed reactor (UAnFFFBR), were compared from kinetic and performance standpoints. As in the previous studies, only the kinetic coefficients have been calculated and the relationship between kinetic coefficients and their interpretation has not been evaluated, the other aim of the present study was to fill this research gap.

RESULTS

In optimum conditions, 90.31 and 86.91% of COD as well as 91.11 and 88.72% of DEP removal were achieved for the AnFFBR and UAnFFFBR, respectively. According to kinetic coefficients (except biomass yield), the AnFFBR had better performance as it provided a more favorable condition for microbial growth. The Grau model was selected as the best mathematical model for designing and predicting the bioreactors' performance due to its high coefficients of determination (0.97 < R²). With regard to the insignificant variations of the calculated Grau kinetic coefficients (K_G) when the organic loading rate (with constant HRT) increased, it can be concluded that both of the bioreactors can tolerate high organic loading rate and their performance is not affected by the applied DEP concentrations.

CONCLUSIONS

Both the bioreactors were capable of treating low-to-high strength DEP wastewater; however, according to the experimental results and obtained kinetic coefficients, the AnFFBR indicated higher performance. Although the AnFFBR can be considered as a safer treatment option than the UAnFFFBR due to its lower DEP concentrations in sludge, the UAnFFFBR had lower VSS/TSS ratio and sludge yield, which could make it more practical for digestion. Finally, both the bioreactors showed considerable methane yield; however, compared to the UAnFFFBR, the AnFFBR had more potential for bioenergy production. Although both the selected bioreactors achieved nearly 90% of DEP removal, they can only be considered as pre-treatment methods according to the standard regulations and should be coupled with further technology.