COD removal from biologically stabilized landfill leachate using Advanced Oxidation Processes (AOPs)

BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Halanaerobium lacusrosei.RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD0 = 1880–9570 mg L−1), salt concentration ([NaCl] = 30–100 g L−1) and liquid upflow velocity (Vup = 1.0–8.5 m h−1) on COD removal from salt (NaCl)‐containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD0 = 1880 mg L−1, and efficiency decreased to 43% on increasing COD0 to 9570 mg L−1 at 20 g L−1 salt concentration. COD removal was in the range 50–60% for [NaCl] = 30–60 g L−1 at COD0 = 5200 ± .100 mg L−1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L−1. Increasing liquid upflow velocity from Vup = 1.0 m h−1 to 8.5 m h−1 provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L−1 to 321 mg L−1 at Vup = 8.5 m h−1, resulting in over 92% COD removal at 30 g L−1 salt‐containing synthetic wastewater.CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. Copyright © 2008 Society of Chemical Industry

Removal of color, COD and determination of power consumption from landfill leachate wastewater using an electrochemical advanced oxidation processes

Hydrogen peroxide (HP) is widely used in advanced oxidation processes (AOPs). This study evaluates the chemical oxygen demand (COD) removal efficiency of Acid Orange 8 (AO 8) at a higher concentration by modified Fenton processes using substituted HP such as tert-butyl hydroperoxide (TBHP) and sodium perborate (SPB) and sodium persulphate (SPS) as oxidants. Under optimal conditions, COD removal was found to be 72.8 and 58.9% at pH 3.0 and 6.5 in the Fenton process in 300 min.The COD removal efficiency of different systems is in the order: Fe2+/SPB>Fe2+/HP>Fe2+/TBHP>Fe2+/SPS indicating the possibility of using SPB as a substitute for HP and SPS. The order of efficiency is attributed, among other factors, to their ability to produce HO. radicals. Various anions are shown to exhibit an inhibitory effect in the order: I->Br->F->Cl->SO42->NO3-. The inhibitory effect of Cl- is observed at higher concentrations than F- and Br-, even though I- displays inhibition at all concentrations. Finally, COD removal kinetics and the degradation mechanism, based on the identified intermediate products, were determined in this study.

The poultry slaughterhouse industry consumes a large volume of potable water for bird processing and equipment cleaning, which culminates in the generation of high strength poultry slaughterhouse wastewater (PSW). The wastewater contains high concentrations of organic matter, suspended solids, nitrogen and nutrients. Most poultry slaughterhouses in South Africa (SA) discharge their wastewater into the municipal sewer system after primary treatment. Due to its high strength, PSW does not meet SA's industrial discharge standards. Discharge of untreated PSW to the environment raises environmental health concerns due to pollution of local rivers and fresh water sources, leading to odour generation and the spread of diseases. Thus, the development of a suitable wastewater treatment process for safe PSW discharge to the environment is a necessity. In this study, a biological PSW treatment process using an Expanded Granular Sludge Bed (EGSB) was evaluated. Response surface methodology coupled with central composite design was used to optimize the performance of the EGSB reactor. The dependant variable used for optimization was chemical oxygen demand (COD) removal as a function of two independent variables, hydraulic retention time (HRT) and organic loading rate (OLR). The interactions between HRT, OLR and COD removal were analysed, and a two factorial (2FI) regression was determined as suitable for COD removal modelling. The optimum COD removal of 93% was achieved at an OLR of 2 g-COD/L/d and HRT of 4.8 days. The model correlation coefficient (R2) of 0.980 indicates that it is a good fit and is suitable for predicting the EGSB's COD removal efficiency.

While palm oil mill effluent (POME) from different sources will have varying characteristics due to the different process flows in mills, efficient monitoring and performance evaluation of anaerobic digesters in POME treatment are crucial to ensure stable biogas production with minimal operational problems. Therefore, this study aims to evaluate and compare the performances of in‐ground lagoon anaerobic digesters under mesophilic conditions in four different biogas plants (BGPs A, B, C and D) located in Malaysia with respect to total chemical oxygen demand (COD) removal and total biogas produced. Results show that all BGPs are still functioning well with satisfactory methane yields (.135–.364 Nm3CH4/kgCOD removed) and COD removal efficiencies (67%–85%). ANOVA analysis shows that organic loading rate (OLR), temperature (T) and recirculation ratio (RR) have significant effects on the COD removal and biogas production of all four plants. BGP B has the highest amount of biogas produced (4.12 × 105 Nm3/month) and COD removal rate amongst other BGPs due to its most stable and lowest T (<40°C), high RR, and consistent and high COD load. Conversely, BGP D has the lowest COD removal and biogas production, which are mainly contributed by a high COD inlet (92 000 mg/L) and a high T in the anaerobic digester (48.7°C). Despite having a similar design of an anaerobic digester, this comparative study reveals that different BGPs will have different optimum operating conditions and limitations, depending not only on the operating conditions of the BGP (OLR, T and RR) but also on the raw POME quality stemming from the palm oil milling process. A future study would be focused on the optimisation of four BGPs for maximum biogas removal.

In the present study, the removal of phenol from synthetic wastewater was evaluated in a fixed bed reactor with up flow sludge blanket filtration (FUSBF) in comparison with a typical USBF system. At hydraulic retention time (HRT) of 24 hours and solid retention time (SRT) of 20 day, the effect of initial concentration of phenol (260-1020 mg/L) on phenol and chemical oxygen demand (COD) removal efficiency (%) was investigated in both systems. The effect of the presence of fixed bed was determined throughout the operational period.The results showed that the FUSBF system had a better ability than the typical USBF system in terms of phenol and COD removal. The average phenol and COD removal at phenol concentration of 312 mg/L was 97.52% and 92.82% for the FUSBF system and 92.80% and 82.18% for the typical USBF system, respectively. At HRT of 24 h and organic loading rate (OLR) of 30 g/m-3.h-1, the amount of phenol removal was 82.1%. At OLR of 30 g/m-3.h-1, role of fixed bed in phenol and COD removal was 25.01% and 29.3%, respectively, overall, the FUSBF system has a higher efficiency and ability than that of typical USBF and can be used for the purification of industrial wastewater containing refractory organic compounds such as phenol.

Advanced oxidation processes which produce hydroxyl radicals with high oxidation potential have come forward among the methods used in the treatment of industrial wastewaters containing organic pollutants that are difficult to biodegrade. The application of UV rays with the fentanyl reactivity showed that the organic material is more fragmented and the degradation rate is higher. In this study, Fenton process and photo-Fenton process were applied to industrial wastewater of paper. In experimental studies, optimum experimental parameters such as iron ion and hydrogen peroxide concentrations, pH, temperature, reaction time, mixing speed and light intensity were determined and processes were compared. 70% color and 51% chemical oxygen demand (COD) removal in the Fenton process; 96% color and 90% COD removal in the photo-Fenton process were obtained. The addition of UV radiation to the oxidation process resulted in better degradation of organic contaminants and enhanced color and COD removal efficiency. Although the optimum reaction time of the Fenton process was 120 minutes, the optimum reaction time of the photo-Fenton process was 60 minutes.

Biohydrogen production from brewery wastewater in an Anaerobic baffled reactor. A preliminary techno-economic evaluation

Wastewater treatment is a global concern, especially in developing countries with limited access to safe and clean facilities, resulting in individuals practicing unsafe and unsustainable human practices. This poses challenges for South African wastewater treatment plants (WWTPs) due to the aging infrastructures and the use of conventional technologies. Also, recent population growth, urbanization, and industrial activities have given rise to contaminating water resources with recalcitrant organic micropollutants (OMPs). Organic micropollutants cause severe environmental pollution, imbalanced ecosystems (aquatic life), human health risks, and oxygen depletion due to accelerated chemical oxygen demand (COD). Apart from the detrimental effects of wastewater on human health and the ecosystem, the United Nations (UN) sustainability development goal of obtaining clean water and sanitation (SDG #6) by 2030 is continuously threatened. Therefore, treating wastewater for reuse in the environment with good quality comes in handy. Against this background, photocatalysis, such as the advanced oxidation process (AOP), is reported as a promising, eco-friendly, and cost-effective technology for degrading organic contaminants (COD) into harmless compounds. However, the TiO2-based photocatalytic process has setbacks, such as recoverability and treatability efficiency, limiting its industrial application. Therefore, this study explored oxide and non-oxide photocatalysts as alternatives to TiO2-based photocatalytic processes for a local South African wastewater treatment. The photocatalysts considered were Titanium dioxide (TiO2), Iron (III) oxide (Fe2O3), Zinc Sulphide (ZnS), and Copper Sulphide (CuS). Their applicability was conducted experimentally by evaluating and optimizing the performance of oxide (TiO2, Fe2O3) and non-oxide (ZnS, CuS) photocatalysts under UV, UV-visible, and natural sunlight irradiation. The One-Factor-at-a-Time (OFAT) approach was used on the photocatalytic system to identify the relationship between the variables that influence the photocatalytic degradation treatment of municipal wastewater. The water quality parameters considered were pH, turbidity (NTU), colour (Pt. Co), and COD (mg/L). By employing the oxides and non-oxides under a constant UV irradiation light source vi and OFAT approach, the catalyst load (0.5-2.5 g/L), mixing speed (30-150 rpm), and exposure time (10-60 minutes) were investigated. Among the photocatalysts, CuS displayed the best results overall for above 50% COD removal efficiency, whilst ZnS was also efficient in removing above 50% turbidity and colour at a catalyst load of 1.5 g/L, mixing speed of 90 rpm, and UV exposure time of 45 minutes. It was established that CuS was the cheapest at R2.01/1.5g as compared to TiO2 at R32.47/1.5g. Subsequently, the photocatalysts were investigated using three different light sources: UV, UV-visible, and sunlight irradiation. UV-visible was the most favourable at a catalyst load of 1.5 g/L, mixing speed of 90 rpm, and irradiation time of 60 minutes. Thus, the high light intensity of UV-visible, 191,000 Lux, enhanced the photocatalytic performance of the four photocatalysts under this study, with the optimum COD removal values at 72.25%, 70.87%, 70.20%, and 46.66% for Fe2O3, ZnS, CuS, and TiO2 respectively. Furthermore, response predictive models were developed as a function of the input factors of the photocatalytic system for the treatment of municipal wastewater. This was done utilizing the response surface methodology (RSM) via the Box Behnken design (BBD) with the best-performing catalyst (CuS) and the best light source (UV visible), at the optimal conditions of catalyst load of 2 g/L CuS, a mixing speed of 120 rpm, and an exposure time of 30 minutes with treatability desirability of 96%. The selected optimal condition was then validated experimentally, and the results obtained were agreeable with the model-predicted values at 95% confidence levels. Moreover, a comparative study with CuS and TiO2 was evaluated with synthetic wastewater (SW) and raw wastewater (RW) at the optimal conditions. The results by CuS demonstrated above 55% COD, turbidity, and colour removal from both the SW and RW compared to the TiO2, which obtained below 35% removal from both SW and RW. Therefore, under the conditions investigated in this study, CuS was found to be the most cost-effective and viable photocatalyst alternative to TiO2 for wastewater treatment. However, the techno-economic and life cycle assessment must be explored to encourage the prospects of the CuS in the water settings

EFEITO DA TAXA DE AERAÇÃO NO DESEMPENHO DE ALAGADOS CONSTRUÍDOS AERADOS INTERMITENTEMENTE JOÃO GABRIEL THOMAZ QUELUZ; LAUREN NOZOMI MARQUES YABUKI E MARCELO LOUREIRO GARCIA Instituto de Geociências e Ciências Extas, Universidade Estadual Paulista, Avenida 24 A,1515, CEP: 13506-900, Rio Claro, SP, Brasil. queluz@fca.unesp.br; lauren.yabuki@unesp.br; marcelo.garcia@unesp.br 1 RESUMO O presente trabalho foi conduzido com o objetivo de avaliar o efeito de diferentes taxas de aeração na remoção de nitrogênio total (NT) e demanda química de oxigênio (DQO) em alagados construídos de fluxo subsuperficial horizontal (ACFH) aerados intermitentemente. Para isso, foram avaliados quatro ACFH em escala piloto utilizando diferentes taxas de aeração (0; 2; 5 e 10 L min-1) com intervalo de aeração intermitente fixo de 3 h d-1 (1h com aeração/7 horas sem aeração). Os sistemas receberam 8,6 L d-1 de efluente sintético, resultando em tempo de detenção hidráulica de 3 dias. Os resultados mostram que os ACFH aerados intermitentemente apresentaram elevada eficiência na remoção de DQO (>97%), NT (>80%) e NH4+ (>97%), enquanto o ACFH sem aeração apresentou menor eficiência na remoção de DQO (93,9%), NT (48,8%) e NH4+ (57,7%). Adicionalmente, os resultados também mostram que os três ACFH aerados intermitentemente obtiveram desempenho similar na remoção de DQO, NT e NH4+. Finalmente, os resultados permitem concluir que a aeração intermitente permite a ocorrência simultânea da nitrificação e da desnitrificação, aprimorando, assim, o desempenho dos ACFH na remoção de NT. Entretanto, o uso de diferentes taxas de aeração não altera a eficiência de remoção de NT e DQO. Palavras-chave: aeração artificial, remoção de DQO, remoção de nitrogênio. QUELUZ, J. G. T.; YABUKI, L. N. M.; GARCIA, M. L. EFFECT OF AERATION RATE ON THE PERFORMANCE OF INTERMITTENTLY AERATED CONSTRUCTED WETLAND 2 ABSTRACT The aim of the present work was to evaluate the effect of different aeration rates on the removal of total nitrogen (TN) and chemical oxygen demand (COD) in intermittently aerated horizontal subsurface flow constructed wetlands (HFCW). Four pilot-scale HFCWs were evaluated using different aeration rates (0, 2, 5, and 10 L min-1) with a fixed intermittent aeration interval of 3 h d-1 (1 h with aeration / 7 h without aeration). The HFCWs received 8.6 L d-1 of synthetic effluent, resulting in a hydraulic retention time of 3 days. The results show that intermittently aerated HFCWs were highly efficient in removing COD (>97%), TN (>80%) and NH4+ (>97%), while the HFCW without aeration showed lower efficiencies in the removal of COD (93.9%), TN (48.8%), and NH4+ (57.7%). In addition, the results also show that the three intermittently aerated HFCW achieved similar performance in the removal of COD, TN, and NH4+. Finally, the results indicate that intermittent aeration allows the simultaneous occurrence of nitrification and denitrification, thus improving the performance of HFCW in removing TN. However, the use of different aeration rates does not alter COD and TN removal efficiencies. Keywords: artificial aeration, COD removal, the nitrogen removal.

Application of electrochemical flow-through oxidation technology in the treatment of concentrated water from nanofiltration and reverse osmosis in the coal chemical industry

Effects of different pretreatment methods on anaerobic mixed microflora for hydrogen production and COD reduction from palm oil mill effluent

This paper presents data for the synthesis and characterization of layer double hydroxides (LDH) and their use for color and chemical oxygen demand (COD) removal from effluents generated by a textile industry. Adsorption studies with raw and biologically treated (activated sludge) textile effluent showed that the pseudo-second order model best fitted the experimental data, leading to adsorption coefficients of 39.1 and 102.9 mgCOD/gLDH for raw and treated effluents, respectively. The best conditions for color and COD removal were obtained at lower values of temperature and pH (25 °C and pH 7) and, in these conditions, an LDH dose of 10 g/L resulted in color removal efficiencies of 56% for samples of raw and 66% for samples of treated effluent. Recycling studies indicated that the reuse of thermally treated LDH led to a progressive loss in the removal efficiencies of COD and color. The reduction was more pronounced with samples of the raw textile effluent. LDH characterization performed before and after each adsorption and regeneration experiment showed that there was no intercalation of dye molecules in the interlayer region of the LDH, indicating that COD and color removal might be due to the adsorption of organic molecules onto the LDH surface.

The discharge of industrial effluent constituting high orthophosphates and organic pollutants in water receiving bodies compromises freshwater quality and perpetuates eutrophication. In this study, an anaerobic–aerobic sequencing batch reactor (SBR) under activated sludge was investigated for orthophosphates and chemical oxygen demand (COD) removal from brewery wastewater. Raw brewery wastewater samples were collected on a daily basis for a period of 4 weeks. The findings of the study are reported based on overall removal efficiencies recording 69% for orthophosphates and 54% for total COD for a sludge retention time (SRT) of 7 days and hydraulic retention time of 18 h at mesophilic temperature conditions of ±25 °C. Moreover, the SBR system showed stability on orthophosphate removal at a SRT ranging from 3 to 7 days with a variation in organic volumetric loading rate ranging from 1.14 to 4.83 kg COD/m3.day. The anaerobic reaction period was experimentally found to be 4 h with the aerobic phase lasting for 14 h. The SBR system demonstrated feasibility on orthophosphates and COD removal with variation in organic loading rate.

Due to the population growth and reduction of water resources, wastewater treatment and reuse vital. As the secondary wastewater treatment processes enable removes a significant amount of P and N, nutrient-rich effluents can cause eutrophication in water bodies. On the other hand, nutrients removal in sewage treatment using mechanical methods is costly and complex. The aquaculture method using Azolla filiculoides could be an appropriate option for removing total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD) from wastewater. Synthetic wastewater has been prepared in the typical range of municipal wastewater. Two g fresh weight of an acclimatized A.filiculoides was floated in sample bowls each one containing 500 CC prepared wastewater. Total nitrogen, TP, and COD removal by Azolla filiculoides for 21-days were optimized and investigated using the response surface methodology (RSM). For this aim, the D-optimal method was used to optimize the three independent variables (TP concentration (10.8-84.6mg l- 1), TN concentration (20-99mg l- 1), and COD concentration (66.26-415mg l- 1)) for their maximum removal efficiency of them. Experiments were performed on 28 runs in which independent variables were measured using a HACH DR 5000 spectrometer. Predicted R-squared for COD, TP, TN removal, and Azolla mass (responses) have been equal to -0.0897, 0.8514, 0.7779, and 0.5645, respectively. The model was used to maximize Azolla growth and maximize removal efficiency of nitrogen, phosphorus, and COD that occurred in minimum concentrations of TN (20mg l- 1), TP (10.8mg l- 1), and COD (66.26mg l- 1). The removal efficiency of Azolla was obtained 77.5 % for COD, 66.8 % for TP, and 78.1 % for TN in the optimum condition of independent variables. Also, increase of Azolla mass was 239 %, with desirability of 0.66. The difference between model prediction and model validation testing for Azolla mass increase, COD, TN, and TP removal was equal to ± 11.6 %, ± 7.9 %, ± 0.0 %, and ± 1.9 %, respectively. Azolla could remove phosphorus in nitrogen deficiency or even lack of nitrogen. Results indicate that removal efficiency has an upward trend as the Azolla growth increases. This kind of fern has a significant effect on removing nitrogen, phosphorus, and COD from an aqueous solution. The removal efficiency of TN, TP, and COD at optimum operating conditions showed good agreement with model-predicted removal efficiency.