UASB Performance and Perspectives in Urban Wastewater Treatment at Sub-Mesophilic Operating Temperature

UASBs present several advantages compared to conventional wastewater treatment processes, including relatively low construction cost facilities, low excess sludge production, plain operation and maintenance, energy generation in the form of biogas, robustness in terms of COD removal efficiency, pH stability, and recovery time. Although anaerobic treatment is possible at every temperature, colder climates lead to lower process performance and biogas production. These factors can be critical in determining the applicability and sustainability of this technology for the treatment of urban wastewater at low operating temperature. The purpose of this study is the performance evaluation of a pilot-scale (2.75 m3) UASB reactor for treatment of urban wastewater at sub-mesophilic temperature (25 °C), below the optimal range for the process, as related to biogas production and organic matter removal. The results show that, despite lower methane production and COD removal efficiency compared to operation under ideal conditions, a UASB can still achieve satisfactory performance, and although not sufficient to grant effluent discharge requirements, it may be used as a pretreatment step for carbon removal with some degree of energy recovery. Options for UASB pretreatment applications in municipal WWTPs are discussed.

The Removal of Binary Mixture of Dyes by Heterogeneous Fenton Oxidation: Kinetics, Product Identification and Toxicity Assessment

The removal of mixture of two azo dyes, Acid blue 29 and Ponceau xylidine, was studied by heterogeneous Fenton and Fenton-type processes using hydrogen peroxide and sodium persulphate as oxidants in the presence of and nano and micro-Fe2O3 particles as catalysts. The synthesised nano-Fe2O3 particles were characterised using analytical techniques viz. FT-IR, TEM, EDX, powder XRD and VSM. We have examined the effects of particle size on the COD removal efficiency and the reusability of the catalyst after optimising pH, and concentrations of catalyst and oxidant. Combination of nano-Fe2O3 and hydrogen peroxide possessed higher COD removal efficiency, which was accelerated in acidic pH and inhibited at pH > 6. Total consumption of hydrogen peroxide confirmed the efficiency of the optimised parameters. The mechanism of the formation of intermediate ions and products are proposed. COD removal and consumption of hydrogen peroxide follow pseudo-first-order kinetics. The toxicity of the solutions was assessed using Aliivibrio fischeri light loss and Escherichia coli growth inhibition assays. Both the assays showed different toxicity levels for the same solution.

Upflow Anaerobic Filter for the Treatment of Wastewater from a Natural Rubber Latex Concentration Unit

In this study, wastewater from a centrifuge rubber latex concentration unit was experimentally treated by an up-flow anaerobic filter (UAF) at variable hydraulic detention time to investigate the COD removal efficiency and the gas production rate. The UAF reactors were made of PVC pipe with an inside diameter of 9.5 cm, 180 cm in height, with a bed volume of 12.8 L, and filled with polyethylene media. The initial COD concentration of wastewater was in the range 4620 - 10400 mg.L-1. HRTs were controlled at 20 days, with the organic loading rate varying from 2.9 to 10.5 kg.day.m-3. The findings show that the COD removal efficiency of the system was in the range of 85% to 92% for the varying organic loading rates. In addition, the specific methane production rate varied from 8.2 to 14 L of CH4 produced/g of COD destroyed/day for the different organic loading rates.

Study on Treatment of Blood from Abattoir using Microbial Fuel Cell (MFC) Technology with Production of Green Energy

Zero energy technologies and sustainable energy production are the two major concerns of present day researches. Microbial fuel cells (MFCs) are bioreactors that extract chemical energy stored in organic compounds, into electric potential, through bio-degradation. The core reason for the high strength of effluent generated from slaughterhouses is animal blood. The current study evaluates the potential of MFC technology to reduce the pollution strength of cattle blood in terms of chemical oxygen demand (COD). The current study was piloted in three stages using lab scale two chambered MFC: The first stage was to determine the best oxidising agent as compared to natural aeration from three accessible options, KMnO4, diffused aeration and tape grass aquatic plant. KMnO4 was found to be the superlative with a 30% reduction in COD in 100 hrs batch reactor and a maximum power of 0.97 mW using 125 mL livestock blood. The second stage of the study optimised the concentration of KMnO4. At 500 mg/L KMnO4 concentration, 50% COD removal efficiency was acquired in a batch reactor of 60 hrs with an average energy output of 1.3 mW. In the final stage on the addition of coconut shell activated carbon with an Anolyte at a rate of 40 mL/125 mL of substrate COD removal efficiency increased to 74.9%.

Performance of two parallel covered lagoon digesters in the treatment of pig farm wastewaters

Pig farming moves a large part of the Brazilian economy. However, due to the high polluting potential, alternatives to treat and take advantage of the effluents must be developed, being the use of digesters a possible solution. This study aimed to evaluate the performance of two parallel covered lagoon digesters (CLD) in the treatment of swine wastewater. Monitoring was performed on a farm installed in Teixeiras, Minas Gerais, Brazil, in terms of COD in the period from August 2018 to July 2019. The study demonstrated that COD removal efficiency in the CLD was 40.2 and 39.5%, which did not indicate a statistical difference at a 5% significance level. The two digesters in parallel were compatible with each other in terms of COD reduction. Furthermore, individually they did not present significant changes in their performance in the summer and winter periods.

Using BCN nanostructure as anode electrode for photoelectrocatalytic degradation of organics: a statistical approach

In this study, boron carbon nitride (BCN) nanostructures were used as photocatalyst which was synthesized in a chemical vapor deposition reactor. Photoelectrocatalysis was used for degradation organic pollutants from produced water. BCN nanostructures were coated on a coil-type copper wire to be as anode electrode in the photoelectrocatalytic process. The effect of different parameters on chemical oxygen demand (COD) removal efficiency from produced water was investigated by a central composite design (CCD) to maximize photoelectrocatalysis influence as one of the most used methods of wastewater treatment. A 12 run Plackett–Burman design was used for screening of the parameters (initial COD, electrical conductivity, applied cell voltage, UV lamp wavelength, H2O2 concentration, residence time, and initial pH) which led to the selection of residence time and initial pH as effective parameters. Since the core goal of this study was to maximize the COD removal efficiency, the steepest ascent method was used to propel these two parameters to the optimum region. Finally, CCD showed that applying photoelectrocatalysis could lead to 88.79% of the COD removal efficiency which would be an optimum value at a residence time of 15.85 min and a pH value of 3.3. Ultimately, this result was confirmed by experimentation at those conditions.

Performance of Food Waste Feeding Pilot Plant Biodigester Operated with Identified Potential Substrate Properties

Anaerobic digestion has been proven as sustainable process technology for organic waste conversion into renewable bio-energy. This study was conducted to evaluate the performance of mono-digestion process for different types of food waste substrates using pilot scale anaerobic bio-digester (1200 L) in terms of biogas production and the chemical oxygen demand (COD) removal efficiency. The biochemical methane potential (BMP) test of rice waste (R), vegetable waste (VW) and coconut meat residue (CMR) were tested at initial volatile solid (VS) loading of 0.1631, 1.1690, 1.0059 g VS/L, respectively at fixed inoculum/substrate (I/S) ratio of 0.5. Further study conducted by using rice waste (R) in pilot plant anaerobic bio-digester (1200L) for 43 days to investigate the reactor performance in term of COD removal efficiency. Interestingly, inoculum used for this study performs very well and able to digest food waste. Results demonstrate that the maximum specific biogas yield (SBY) was observed from rice waste (R) at 0.0587 L/kg VS compared to other substrates. Specific biogas yield (SBY) of rice waste (R) was 16.01% and 11.92% higher than substrate vegetable waste (VW) and coconut meat residue (CMR) respectively. High COD removal efficiency of pilot plant bio-digester (up to 93 %) using rice waste (R) as sole substrate indicates a good performance of reactor in treating food waste. Conversion of food waste to biogas in pilot plant bio-digester is highly potential as one of the sustainable waste treatment technology.

Investigating the Result of Current Density, Temperature, and Electrolyte Concentration on COD: Subtraction of Petroleum Refinery Wastewater Using Response Surface Methodology

Electrochemical oxidation (EO) investigated chemical oxygen demand (COD) subtraction from petroleum refinery wastewater (PRW) as a capable remediation process. Titanium substrates coated with iridium–tantalum oxide mixtures (Ti/IrO2–Ta2O5) were used as the dimensional stable anode (DSA). The Box-Behnken Design (BBD), a statistical experimental design and response surface methodology (RSM), was used to matrix the current density, temperature, and electrolyte (NaCl) concentration variables, with COD removal efficiency as the response factor. A second-order verifiable relationship between the response and independent variables was derived where the analysis of variance displayed a high coefficient of determination value (R2 = 0.9799). The predicted values calculated with the model equations were very close to the experimental values where the model was highly significant. Based on the BBD for current density, the optimum process conditions, temperature and electrolyte (NaCl) concentration were 7.5 mA/cm2, 42 °C and 4.5 g/L, respectively. They were resulting in a COD removal efficiency of 99.83% after a 12-hour EO period.

Bioremediation of cardboard recycling industry effluents using mixed fungal culture

Purpose This paper aims to evaluate the bioremediation [chemical oxygen demand (COD) and color removal] of the effluent from the cardboard recycling industry in Yazd, central province of Iran, using mixed fungal culture. Design/methodology/approach First, the effluent samples from the cardboard recycling industry were cultured on potato dextrose agar medium to isolate native fungal colonies. The grown colonies were then identified using morphological macroscopic and microscopic characteristics to choose the dominant fungi for bioremediations. The mixed cultures of Aspergillus niger, Aspergillus flavus and Penicillium digitatum were finally used for bioremediation experiments of the cardboard recycling industry. A suspension containing 1 × 106 CFU/ml of fungal spores was prepared from each fungus, separately and their homogenous mixture. Sewage samples were prepared and sterilized and used at 25%, 50% and 90% dilutions and pH levels of 5, 7 and 8 for bioremediation tests using mixed fungal spores. Following that, 10 ml of the mixed fungal spores were inoculated into the samples for decolorization and COD removal and incubated for 10 days at 30°C. The amount of COD removal and decolorization were measured before incubation and after 3, 6 and 10 days of inoculation. In this research, the color was measured by American Dye Manufacturer Institute and COD by the closed reflux method. The results of the present study were analyzed using SPSS 21 statistical software and one-way ANOVA tests at p-value < 0.05. Findings The results of this research showed that the mean decolorization by mixed fungal culture over 10 days at pH levels of 5, 7 and 8 were 44.40%, 45.00% and 36.84%, respectively, and the mean COD removal efficiency was 71.59%, 73.54% and 16.55%, respectively. Moreover, the mean decolorization at dilutions of 25%, 50% and 90% were 45.00%, 31.93% and 30.53%, respectively, and the mean COD removal efficiency was 73.54%, 62.38% and 34.93%, respectively. Therefore, the maximal COD removal and decolorization efficiency was obtained at dilution of 25% and pH 7. Originality/value Given that limited studies have been conducted on bioremediation of the effluent from the cardboard recycling industry using fungal species, this research could provide useful information on the physicochemical properties of the effluent in this industry.

Treatment of simulated printing and dyeing wastewater using ozone microbubble

Owing to its widespread and persistent usage, methylene blue (MB) is an environmental substance, mostly found in the printing and dyeing industry that raises concerns in the environment recently by posing significant threat to human life and the ecosystem as a whole. Thus, there is the need to effectively manage and treat the wastewater from these industries before reaching to the available water sources. Ozonation treatment is very efficient in treating printing and dyeing wastewater (MB) and can be greatly improved by using micro-bubble technology. Microbubble dissolution is an effective way to improve the rate of ozone mass transfer. To discover these properties, a method was used to improve the mass transfer of ozone microbubbles, which was used to effectively treat simulated printing and dyeing wastewater. We investigated the effects of pH, water temperature, ozone flow, and other conditions on the dissolution and attenuation properties of ozone in methylene blue microbubble solutions. Treatment of simulated printing and dyeing wastewater (methylene blue) was investigated under various initial pH and ozone flow rates. A catalytic exhibition was performed towards the decolorization of methylene blue (MB) concentrations and the corresponding COD removal efficiency. Ozone depletion and pH levels played key roles in MB degradation. Under high pH level of 11.01, the rate of removal of COD was 93.5%. Ozone dosage also has direct effect on COD removal efficiency and decolorization. Higher ozone flow rates, 0.4 L/min and 0.5 L/min recorded more than 94% degradation of COD thus very effective and efficient. Also, ozone flow rates 0.3 L/min, 0.4 L/min and 0.5 L/min with initial pH, 7.03, 6.63 and 6.36 decreased to 3.43, 3.49 and 3.44 after reaction processes which clearly shows that with high ozone dosage, pH reduces considerably.