Post-treatment Of Anaerobic Effluent Research Articles

Characterization of Anaerobic Effluent: Seasonal Influence and Use of Anammox Process as Post-treatment

This study aimed to verify if subtropical annual seasonality variation of organic matter and nitrogen ratio facilitates the use of anammox process as a post-treatment of anaerobic effluent. We characterized the anaerobic effluent from a wastewater treatment plant (WWTP) located in Campinas, SP, Brazil. The collected composed samples were from an UASB reactor in different days, hours, and months during 1 year. The mean temperature of all seasons was above 19 °C, which favors anammox activity, and seemed to influence much more than that of pluviosity on effluent composition. It may be explained by the separated sewage collection in Brazil, which is not constructed to receive and transport rainwater, although some not predicted connection may be added in. We also concluded that subtropical annual seasonality of COD/N ratio range (2.2 to 3.1) from anaerobic effluent indicates that the use of anammox process is suitable as post-treatment of anaerobic effluent in subtropical areas. However, as total COD degrades over time and as total nitrogen concentration is influenced by seasons, these factors need to be taken into account in the project and operation of the reactor over the year.Graphical abstract

Performance of biological activated carbon (BAC) filtration for the treatment of secondary effluent: A pilot-scale study

In addition to the adsorption capability for organic compounds, granular activated carbon (GAC) can also serve as a good media for the growth of microbial communities in biofilters. Despite its potential, the application of BAC filtration for municipal wastewater treatment has been little addressed in the literature. In this context, this paper aimed to investigate BAC filtration as a post-treatment of anaerobic effluent in pilot scale and its performance in removing organic matter and turbidity. Removal efficiencies during the biofilters run times and along biofilters depth were also evaluated. Three BAC filters were evaluated under different operating conditions of filtration rates (from 13 to 32 m d−1) and empty bed contact time (EBCT) (from 45 to 112 min) during 170 days. The lowest filtration rate (13 m d−1) presented the best performance in terms of dissolved organic carbon (DOC) removal (68.2 ± 4.0%), leading to mean DOC effluent concentration of 6.8 ± 0,9 mg L−1. The BAC reached the stability of biological activity from the 63rd day of operation, however, the adsorption process was still occurring contributing to DOC removal. These DOC removals were higher than those results reported in the literature for BAC filters treating drinking water and municipal wastewater. The DOC removal efficiencies were maintained during the filter run times, showing the robustness of the system even after the interference caused by the backwashing process. BAC filtration was also capable of removing turbidity, with removal efficiencies between 84.5 ± 3.6% and 70.63 ± 6.8% depending on the filtration rate. The results indicated the capability of BAC systems to remove efficiently organic carbon and turbidity from effluents with high organic content, mean of 23.97 (±3.96) mg.L−1, and also valuable support to determine adequate operating parameters for BAC filters application in secondary effluent treatment, such as filtration rate (13 m d−1), EBCT (112 min), and detailed backwashing procedures.

Performance assessment of aerobic granulation for the post treatment of anaerobic effluents

Abstract Present study investigates the formation of aerobic granular biomass and its comparative performance in treatment of anaerobic effluents using two lab scale sequencing batch reactors (SBR), (Reactor 1 and 2) fed with medium strength synthetic wastewater and anaerobic effluent respectively. The granulation was better in reactor 1 with biomass concentration of 7014 mg/L while in reactor 2 it could reach only 3910 mg/L. Reactor 1 showed good organic and nitrogen removal performance. The COD removal efficiency in reactor 1 was more than 90% (average ∼ 94 ± 2%) reaching to a maximum of 98% with influent concentration of 1400 ± 12 mg/L. While in reactor 2, it was only 55 ± 9% reaching to a maximum of 64% with influent concentration of 213 ± 47 mg/L. Total nitrogen removal efficiency with influent of 140 ± 3 mg/L in reactor 1 was more than 90% compared to average removal efficiency of 78 ± 7% with influent of 84 ± 25 mg/L in reactor 2. Reactor 1 showed better nitrate removal of 91 ± 9%(influent nitrate concentration of 53 ± 6 mg/L) while as reactor 2 showed better ammonia removal of 87 ± 25% with influent concentration of 67 ± 29 mg/L. Sludge characterization by Scanning Electron Microscopy and Fourier Transforms Infrared Spectroscopy revealed bacterial morphologies of rod, coccus and filament coexisted in the granules. The preliminary findings in this study may supplement insights about application of aerobic granulation in post treatment of anaerobic effluents.

Vertical flow constructed wetland planted with Heliconia psittacorum used as decentralized post-treatment of anaerobic effluent in Southern Brazil

In order to investigate the potential of vertical flow constructed wetlands (VFCWs), a 24.5 m2 surface area filled with gravel and planted with Heliconia psittacorum, was implemented as an experimental system for domestic wastewater treatment in southern Brazil. The aims of the study were to (i) evaluate the performance of a full scale system septic tank (ST) and VFCW for decentralized domestic wastewater treatment, and (ii) identify the influence of Heliconia for hydraulic characteristics and consequent performance of the VFCW. The applied load rates in the VFCW were, on average, 10 g biochemical oxygen demand (BOD) m−2 day−1, 4 g NH4+-N m−2 day−1 and a hydraulic loading rate (HLR) of 60 mm day−1. Physicochemical analyses of wastewater treatment were carried out through grab sample methodology, for 5 months. Additionally, hydrodynamic tests were performed during plant development using rhodamine. The study demonstrated the viability of the system for decentralized wastewater treatment in Brazil, with average removal efficiencies of 78% for chemical oxygen demand (COD) and 84% for total suspended solids (TSS), according to national effluent discharge regulations. In spite of media’s large size, the VFCW achieved good average removal efficiencies. The tracer test results showed that the VFCW average hydraulic detention time increased as plants grew. This may have occurred due to interception of wastewater applied on the macrophyte’s leaves as well as a reduction in filter media permeability caused by the spread of roots and rhizomes. These results indicate that the plants played an important role in increasing wastewater contact time in wetlands with high hydraulic conductivity such as a gravel VFCW.

Post-treatment of anaerobic effluent containing 1,4-dioxane and heavy metals via auto-aerated down-flow hanging luffa (ADHL) system

Abstract Biodegradation of anaerobic effluent containing 1,4-dioxane and heavy metals via auto-aerated down-flow hanging luffa (ADHL) system was extensively investigated. The oxygen was naturally supplied to the consortium bacterium through windows located along the reactor height creating favorable aerobic conditions. The bioreactor efficiently removed 1,4-dioxane and total chemical oxygen demand (CODt) from anaerobic effluent without significant inhibitory effects. Removal efficiencies of CODt and 1,4-dioxane were significantly increased from 31.3 ± 10 to 59.5 ± 5.9% and from 43.7 ± 11.9 to 90 ± 4.9% at increasing the hydraulic retention time (HRT) from 5.7 to 17.3 h, respectively. Moreover, ADHL system was very effective for removal of heavy metals (Cr6+, Cu2+, Fe3+, Mn2+, Ni2+) where the extracellular polymeric substances (EPS) concentrations were quite high and amounted to 12.3 ± 1.3 g/g biomass at an HRT of 17.3 h. The nitrification efficiency was 3.0, 46.8 and 56.3% at HRTs of 5.7, 11.5 and 17.3 h, respectively. Batch experimental results showed that the key removal mechanism of 1,4-dioxane was adsorption followed by biodegradation process.

Remoção de nutrientes por meio de algas sob diferentes condições de iluminação

O presente estudo teve como objetivo avaliar o crescimento de algas e a remoção de nutrientes (nitrogênio e fósforo) empregado no pós-tratamento de efluentes de reatores anaeróbios (UASB), em diferentes condições de iluminação por diodo de emissão de luz (LED). Os resultados mostraram que a iluminação LED não afeta o crescimento das algas, resultando em valores muito próximos aos com iluminação natural (luz do dia). Em relação ao nitrogênio e fósforo, a concentração obtida no efluente final foram < 1,5mgN/L e < 2,5mgP/L, com eficiências superiores a 96%.

Isolation and characterization of a microorganism involved in sulfide-oxidizing autotrophic denitrification in a vertical fixed-bed reactor

This study evaluates the microbial community involved in autotrophic denitrification by sulfide oxidation, applied in the post-treatment of anaerobic effluent. The enrichment of the bacterial community and autotrophic denitrifying community was performed with biomass samples collected from a vertical fixed bed reactor operated under the following condition: autotrophic nitrate reduction with excess sulfide. The nitrate reduction condition with N/S ratio of 0.8 showed the highest concentration of autotrophic denitrifying microorganisms. The isolated bacterium was identified as Pseudomonas stutzeri - like organism. The maximum specific growth rate of the population (μmax) was 0.037h−1, with doubling time of 18.7h. The cell yield (Y) was 0.15gSSVgN−1 and denitrification rate was of approximately 0.24gNgSSVh−1. The data obtained point to the feasibility of applying the isolated species in the autotrophic denitrification process using sulfide as electron donor.

Post-treatment of anaerobic effluent by ozone and ozone/UV of a kraft cellulose pulp mill.

Pulp and paper mill effluents represent a challenge when treatment technologies are considered, not only to reduce organic matter, but also to reduce the toxicological effects. Although anaerobic treatment has shown promising results, as well as advantages when compared with an aerobic system, this process alone is not sufficient to reduce recalcitrant compounds. Thus, an advanced oxidation process was applied. This experiment was performed to determine the effect of ozone and ozone/UV treating a horizontal anaerobic immobilized biomass reactor effluent from a kraft cellulose pulp mill for 306 days with an organic volumetric load of 2.33 kgCOD/m³/day. The removal of organic compounds was measured by the following parameters: adsorbable organically bound halogens (AOX), total phenols, chemical oxygen demand (COD), dissolved organic carbon and absorbance values in the UV-visible spectral region. Moreover, ecotoxicity and genotoxicity tests were conducted before and after treatment with ozone and ozone/UV. At an applied ozone dosage of 0.76 mgO₃/mgCOD and an applied UV dosage of 3.427 Wh/m(3), the organochlorine compounds measured as AOX reached removal efficiencies of 40%. Although the combination of ozone/UV showed better results in colour (79%) and total phenols (32%) compared with only ozone, the chronic toxicity and the genotoxicity that had already been removed in the anaerobic process were slightly increased.

Hydrodynamics of a Bench-Scale Aerated Post Treatment Unit for Up-Flow Anaerobic Sludge Blanket Reactor

The major issues in anaerobic treatment are discharge standard accomplished by post-treatment facilities. Model tanks have been designed for post treatment of anaerobic effluents. Tracer studies by KMnO4 have been employed on model tanks to know hydrodynamics and mixing inside the tanks. The existence and arrangement of baffles in the tanks and higher tracer density can result in much more complex flow pattern which includes turbulent mixing, dead zones and short circuiting. The objective of the paper is to present the result of a numerical study undertaken to investigate the flow inside the reactor and effect of hydraulic parameters on the extent of mixing. The computational fluid dynamics (CFD) study was also performed on the velocity distribution within the model tanks. Thus, several 2D steady-state and time-variable numerical simulations were performed with in the model tanks geometry. Tracer transport was analyzed in case of burst of concentration. The CFD study shows how velocity, pressure and their vector notations were useful to predict the dead spaces inside the tanks which affect the mixing behavior inside the tank.

Mesophilic and thermophilic activated sludge post treatment of anaerobic effluent. Sludge and wastewater characterisation using batch experiments.

Anaerobic pretreated paper process water was characterized in terms of readily biodegradable, slowly biodegradable, very slowly biodegradable and inert wastewater fractions under mesophilic and thermophilic conditions. The anaerobic pretreated paper process water contained a relatively high amount of slowly biodegradable components and few easily biodegradable components as indicated by the ratio of short-term BOD over the BOD5. Wastewater readily biodegradable COD, determined as short-term BOD, was almost similar when measured under both temperature conditions. Fractions of slowly biodegradable COD and inert COD of the same wastewater were found to depend on the type of biomass involved in the test. Thermophilic aerobic biomass was not able to degrade the wastewater to the same extent as the mesophilic biomass resulting in higher apparent inert COD levels. Furthermore, wastewater colloidal COD did not flocculate under thermophilic conditions and was thus not removed from the liquid phase.

Post-treatment of anaerobic effluents in constructed wetland systems

This papers describes the behaviour of wetlands as a post-treatment unit for anaerobically treated sewage for the removal of organic matter, suspended solids, nutrients (nitrogen and phosphorus) and faecal coliforms. Raw sewage was treated in a UASB reactor with a retention time of 5 h and the effluent was used in four units of wetlands with coarse sand as the medium and operated with different hydraulic loads. Three of the units had emerging macrophytes (Juncus sp), whereas the fourth one was operated as a control unit without plants. During the 12 months of operation, the organic material removal efficiency (measured as COD) was in the range of 79 to 85%, whereas suspended solids removal varied from 48 to 71%. Faecal coliform removal was very high (99.99%); phosphorus was also efficiently removed (average efficiency of 90% for the lowest hydraulic load), but nitrogen removal was only partial (45 to 70% for ammonia and 47 to 70% for TKN). The experimental results clearly show the technical feasibility of using wetlands for treatment of municipal sewage after a pre-treatment in the UASB reactor.