Treatment Of Anaerobic Effluent Research Articles

Ozonation process at neutral pH integrated with anaerobic treatment system to methylparaben removal

The incomplete removal of emerging pollutants, such as parabens, from wastewater effluents represents a major pathway for their release into the environment. The development of advanced technologies integrated into well-known conventional systems is a solution. Advanced oxidative processes (AOP), such as ozonation and its combinations, are technologies based on the generation of hydroxyl radicals (HO•) capable of removing these pollutants, representing an alternative solution to this problem. Therefore, the present study aimed to investigate the ozonation process combined with hydrogen peroxide (O3/H2O2) in the treatment of anaerobic effluent post-treated by a real-scale upflow anaerobic sludge blanket (UASB) reactor, enriched with methylparaben (MeP). The study was conducted under optimized conditions and at neutral pH of the effluent. To investigate the influence of variables, as ozone concentration, hydrogen peroxide concentration, pH and time, a 24 Factorial experimental design followed by a 22 Doehlert optimization design was implemented. The optimal degradation occurred with 25.0 mg L−1 of O3 and 30.0 mg L−1 of H2O2 at neutral effluent pH, achieving a removal efficiency of 71.6 % after 60 min and 85.5 % after 120 min. The optimized O3/H2O2 process after 60 min achieved a 95.0 % removal of organic matter by biochemical oxygen demand (BOD), reducing the initial concentration from 138 mg L−1 to 7 mg L−1. Acute toxicity test with Artemia salina and Lactuca sativa, indicated an absence of toxicity (TU < 0.4). The findings of this study indicate the positive efficiency of combining post-UASB effluent treatment with O3/H2O2 processes for the removal of methylparaben.

Understanding photochemical adaptations of microalgal ammonium extremophiles to elevated ammonium concentrations in abattoir anaerobic digestate

Identifying microalgal species with outstanding environmental resistance to NH4+ toxicity is critical to developing effective algal-based anaerobic effluent treatment. This is the case for two microalgal NH4+ extremophiles, Chlorella sp. MUR269 and Scenedesmus sp. MUR270 well suited to treat high nitrogen digestates. However, their exact tolerance mechanisms to high NH4+ conditions still need to be understood. A chlorophyll fluorescence approach based on high-throughput pulse amplitude-modulated fluorimetry was used to understand the photochemical adaptations of these species under increasing NH4+ concentrations (0, 100, 200 mgNL−1) derived from abattoir anaerobic digestate. Both species tolerated 200 mgN-NH4+L−1 in the digestate by exhibiting different photochemical mechanisms. Chlorella decreased its PSII primary photochemistry efficiency (Fq′/FM′) and maximum electron transport (rETRmax) immediately after exposure to the treatment conditions. In contrast, Scenedesmus maintained unaltered Fq′/FM′ regardless of NH4+-N concentration, while rETRmax was significantly reduced to a level of Chlorella at 200 mgNL−1. Energy transduction parameters showed Chlorella increased the size of its reaction centre antennae to capture more photons, which increased the trapping flux ratio and maintained efficient dissipation of excess energy. Conversely, Scenedesmus displayed reductions in the absorbed, trapped and dissipated energy fluxes, though its transported flux for photochemical energy production was similar to Chlorella sp. The energetic communication and connectivity between Chlorella PSII units went up by 47 % and 40 % when the NH4+-N level increased from 50 to 100 and N200 mgL−1, respectively, while Scenedesmus exhibited a dose-dependent decrease in the connectivity between its PSII components. The photosynthetic performance index revealed that the overall energetic flux processing efficiency by Scenedesmus was 86 % (50 mgNL−1), 73 % (100 mgNL−1) and 91 % (200 mgNL−1) higher than Chlorella sp. Thus, the two chlorophytes maintained their overall photochemical capacity by simple, economic biological mechanisms involving adjustments of antenna size and energetic communications between PSII neighbour units.

Achievement and microbial profiles of non-aerated partial nitrification in photo sequencing batch and continuous flow reactors

Nitrite accumulation could be achieved in algal-bacterial consortia without energy-intensive aeration, which could be a sustainable alternative for wastewater treatment. However, few studies focused on the achievement of partial nitrification in different non-aerated algal-bacterial systems and the related microbial mechanisms are still unclear. Here two different algal-bacterial systems (photo-sequencing batch reactor (PSBR) and up-flow sludge blanket bioreactor (PUSB)) were operated for anaerobic effluent treatment and the non-aerated partial nitrification was evaluated. Results showed that the nitrite accumulation rates in the PSBR and PUSB were 92.70 ± 7.81 % and 81.44 ± 11.28 %, respectively, which was constant with microbial activities. Denser algal-bacterial granules were observed in the PSBR, whereas looser algal-bacterial flocs were in the PUSB. Phormidium and Leptolyngbya (i.e., two filamentous cyanobacteria) were enriched in the PSBR and PUSB, respectively, and the higher enrichment of Nitrosomonas and complete inhibition of Nitrospira contributed to better partial nitrification of PSBR. The PUSB had more intensive interspecific interactions and more cooperative behavior in microbial network. Metagenomic analysis revealed that partial denitrification might partially contribute to the nitrite accumulation in the PUSB owing to higher nitrate reductase gene expressions. Overall, this study advances our understandings of the partial nitrification process and nitrite accumulation by algal-bacterial consortia.

Inorganic carbon limitation during nitrogen conversions in sponge-bed trickling filters for mainstream treatment of anaerobic effluent

Anaerobic sewage treatment is a proven technology in warm climate regions, and sponge-bed trickling filters (SBTFs) are an important post-treatment technology to remove residual organic carbon and nitrogen. Even though SBTFs can achieve a reasonably good effluent quality, further process optimization is hampered by a lack of mechanistic understanding of the factors influencing nitrogen removal, notably when it comes to mainstream anaerobically treated sewage. In this study, the factors that control the performance of SBTFs following anaerobic (i.e., UASB) reactors for sewage treatment were investigated. A demo-scale SBTF fed with anaerobically pre-treated sewage was monitored for 300 days, showing a median nitrification efficiency of 79% and a median total nitrogen removal efficiency of 26%. Heterotrophic denitrification was limited by the low organic carbon content of the anaerobic effluent. It was demonstrated that nitrification was impaired by a lack of inorganic carbon rather than by alkalinity limitation. To properly describe inorganic carbon limitation in models, bicarbonate was added as a state variable and sigmoidal kinetics were applied. The resulting model was able to capture the overall long-term experimental behaviour. There was no nitrite accumulation, which indicated that nitrite oxidizing bacteria were little or less affected by the inorganic carbon limitation. Overall, this study indicated the vital role of influent characteristics and operating conditions concerning nitrogen conversions in SBTFs treating anaerobic effluent, thus facilitating further process optimization.

Control of sulfides and coliphage MS2 using hydrogen peroxide and UV disinfection for non-potable reuse of pilot-scale anaerobic membrane bioreactor effluent

Anaerobic membrane bioreactors reduce the energy cost of wastewater treatment and meet filtration requirements for non-potable reuse. However, sulfides (H2S/HS−) formed during anaerobic treatment exert a high chlorine demand and inhibit UV disinfection by photon shielding at 254 nm. This study evaluated the feasibility of hydrogen peroxide (H2O2) for sulfide oxidation, UV disinfection for inactivation of MS2 bacteriophage, and chlorine to provide a residual for distribution. H2O2 treatment at pH ≥ 8 favored sulfide oxidation to sulfate in 30 min at a 4:1 H2O2:sulfide stoichiometry. Compared to a 6:1 H2O2:sulfide molar ratio, treatment of anaerobic effluent with 0.5 mM sulfides with a 4:1 H2O2:sulfide molar ratio would increase the applied UV fluence needed for 5-log MS2 inactivation from 180 mJ cm−2 to 225 mJ cm−2. However, the lower H2O2 dose reduced the dose of chlorine needed to quench residual H2O2 and provide a residual for distribution. Treatment at the 4:1 H2O2:sulfide molar ratio was favored, because the cost savings in H2O2 and chlorine reagents outweighed the energy savings associated with UV treatment. However, H2O2/UV/chlorine treatment of anaerobic effluent was cost-competitive with conventional treatment of aerobic effluent for non-potable reuse only for < 285 µM sulfides.

Part B: Advances in gas emission control techniques for anaerobic-based STPs Technical Note 8 – Emission and mathematical models of dispersion of odorants gases generated in the STPs

Companies related to environmental sanitation, such as sewage treatment plants (STP), especially those based on anaerobic effluent treatment, are faced with the need to evaluate their odorous gaseous emissions, aiming to reduce any impacts on the environment and on the surrounding community, since odorant gases emission has a real impact on people and their well-being, in addition to being one of the main reasons related to complaints and nuisance around the STP. In this context, this Technical Note discusses: (i) the application of the dynamic flux chamber for the direct measurement of volatile gas in units that have quiescent liquid surfaces (low degree of agitation); (ii) the use of algebraic mathematical models to estimate the emission rate of odorants gases in the units of a STP; and (iii) the use of dispersion models as tools to evaluate the concentration of pollutants after their emission. The required input data from each model is highlighted as well as the limitations of each process.

Enzymatic pretreatment and anaerobic co-digestion as a new technology to high-methane production.

The population growth is causing an increase in the generation of effluents (mainly organic fraction of municipal solid waste (OFMSW) and agro-industrial waste), which is an old problem in agro-industrial countries such as Brazil. Contrastingly, it is possible to add value to these residual biomasses (residues) through the application of new technologies for the production of bioenergy. Anaerobic digestion (AD) of sewage sludge is being applied in many effluent treatment plants for the sustainable and economically viable production of biogas. However, the biogas produced from AD (sludge) or co-digestion (sludge with other residues) presents a concentration of methane between 60 and 70% on average, which is relatively low. This review is aimed at analyzing studies involving (i) production of lipases by solid-state fermentation (SSF) by different microorganisms for the application in enzymatic pretreatments prior to the anaerobic treatment of effluents; (ii) pretreatment followed by AD of various residues, with an emphasis on OFMSW and sewage sludge; and (iii) more recent studies on anaerobic co-digestion (AcoD) and hybrid technologies (pretreatment + AD or AcoD). There are many studies in the literature that demonstrate the enzymatic pretreatment or AcoD applied to the optimization of methane production. Nevertheless, few studies report the combination of these two technologies, which can improve the process and reduce or eliminate the costs of biogas purification, which are major challenges for the viability of this route of bioenergy production. KEY POINTS: • Municipal and agro-industrial wastes have potential as medium for lipase production. • Enzymatic pretreatment and anaerobic co-digestion are low cost for high-methane production. Graphical abstract Interactions among various factors optimization methane production from enzymatic pretreatment and AcoD.

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.

Filamentous microalgae Tribonema sp. cultivation in the anaerobic/oxic effluents of petrochemical wastewater for evaluating the efficiency of recycling and treatment

The filamentous microalgae Tribonema sp. was cultured in the effluents of different stages (the primary clarifier, the anaerobic and the anaerobic/oxic) of the traditional Anaerobic/Oxic (A/O) process for evaluating the recycling and treatment efficiency of the petrochemical wastewater in this paper. It was observed that Tribonema sp. grew in the anaerobic effluent had the ideal growth states and wastewater treatment efficiency. The biomass concentration, the chemical oxygen demand (COD), and total nitrogen (TN) removal rates were 4.4 g/L, 98.4% and 96.8%, respectively, for Tribonema sp. grown in the anaerobic effluent. Moreover, the total phosphorus (TP) and organic contaminants were almost completely removed and the oil content of the microalgae reached the highest (36.1%) in the anaerobic effluent. The filamentous microalgae Tribonema sp. cultivation directly integrated with the treatment of anaerobic effluents is demonstrated as an alternative approach to the traditional oxic stage in the A/O process.

English

The use of a biosurfactant surfactin produced by Bacillus subtilis LB5a in cassava growth medium (cassava wastewater) was evaluated to treat anaerobically, the effluent from a poultry slaughterhouse. During the effluent pretreatment, effects of surfactin concentration factors were evaluated, considering the ones which were superior and below its critical micelle concentration (CMC = 28 mg L-1): 6, 13, 27, 31, 48, 73 and 56 mg L-1 and temperature (25, 30, 42.5, 55 and 60&deg;C) up to 6 h, using the rotational central composite design. During anaerobic treatment, flasks were filled with anaerobic sludge as inoculum and a pretreated effluent for 4.5 h in its different concentrations of surfactin. Reactors were connected to eudiometers under static system at 34&deg;C. During the pretreatment phase, there was a direct ratio between temperature and surfactin concentrations according to the increase of organic matter solubilization, measured by soluble chemical oxygen demand (SCOD). These results have shown surfactin applicability produced by B. subtilis LB5a during the anaerobic treatment of effluent from a poultry slaughterhouse; as for all treatments, there was no inhibition of microbial consortium of the anaerobic sludge. SCOD removal was above 80%, while oil and greases removal was above 70%, plus a propitious specific methane yield. Key words: Bacillus subtilis, agro-industrial effluents, anaerobic sludge.

Enzymatic hydrolysis and anaerobic biological treatment of fish industry effluent: Evaluation of the mesophilic and thermophilic conditions

Enzymatic hydrolysis and anaerobic treatment of effluent similar to that generated in the fish processing industry were evaluated at 30 °C and 50 °C. Hydrolysis used lipase produced by fungus Penicillium simplicissimum in solid state fermentation with babassu cake as substrate, which has optimal activity at 50 °C. Hydrolysis kinetics was conducted with mixtures of effluent (containing 1500 mg oils and greases/L) and different lipase activities (0–0.67 U/ml of effluent), verifying that with 0.16 U/ml of effluent, 9.69 μmol/ml of free acids were produced after 4 h at 50 °C. Anaerobic biodegradation assays were conducted with effluent submitted to three different treatments: thermophilic (hydrolysis and anaerobic treatment at 50 °C), mesophilic (hydrolysis and anaerobic treatment at 30 °C) and hybrid (hydrolysis at 50 °C and anaerobic treatment at 30 °C). The best results (97.5% of chemical oxygen demand [COD] removal and 105.4 ml CH4/g CODremoved) were obtained with the hybrid treatment in only 68 h. The thermophilic hydrolysis not only reduced the amount of enzyme and the hydrolysis time but also reduced the time and the cost of mesophilic anaerobic treatment, favoring the application of this treatment on an industrial scale.

Sustainable and integrated palm oil biorefinery concept with value-addition of biomass and zero emission system

The problem of biomass residues and effluent from the palm oil milling process has become a big concern for the industry, the public and the environment. Furthermore, the modern palm oil mill can no longer rely solely on traditional crude palm oil and palm kernel products for profit generation. In order to remain truly sustainable in the future, we propose the solid biomass residues and liquid effluent to be managed and utilized via a biorefinery concept to generate new value-added products, in-line with zero emission system. Modern and efficient boiler and turbine systems utilizing biomass and biogas captured from the anaerobic effluent treatment can provide the steam and electricity required for the palm oil mill operations. The solid biomass residues can be channeled towards the production of value-added products such as biofertiliser, biochar, biofuels and biomaterials. The liquid final discharge can be further treated to meet river water quality, making it suitable to be recycled - hence achieving zero emission. Such an integrated approach will not only solve the issue of proper biomass disposal and effluent treatment, but also more importantly create a win-win-win situation for profit, people and planet - the three pillars of sustainability.

Effect of Microalgae/Activated Sludge Ratio on Cooperative Treatment of Anaerobic Effluent of Municipal Wastewater

In this work, capability of the green microalga (MA), Chlorella vulgaris, in treating synthetic anaerobic effluent of municipal wastewater was investigated. While pure C. vulgaris (100 % MA) provided maximum soluble chemical oxygen demand (sCOD) and N-NH4(+) removal efficiencies of 27 and 72 % respectively, addition of activated sludge (AS) to MA in different mass ratios (91, 80, 66.7, 9 % MA) improved wastewater treatment efficiency. Thus giving maximum sCOD and N-NH4(+) removal efficiencies 85 and 86.3 % (for MA/AS = 10/1), respectively. Utilizing AS without C. vulgaris, for treating the synthetic wastewater resulted in 87 % maximum sCOD and 42 % maximum N-NH4(+) removal efficiencies. Furthermore, algal growth and specific growth rates were measured in the systems with microalga as the dominant cellular population. As a result, faster algal growth was observed in mixed systems. Specific growth rate of C. vulgaris was 0.14 (day(-1)) in 100 % MA and 0.39 (day(-1)) in 80 % MA. Finally, data gathered by online measurement of dissolved oxygen indicate that algae-activated sludge mixture improves photosynthetic activity of examined microalga strain during anaerobic effluent treatment.

Application of Home-Made Enzyme and Biosurfactant in the Anaerobic Treatment of Effluent with High Fat Content

The SSF lipase production from Penicillium simplicissimum using an agro industrial residue and the biosurfactant from Pseudomonas aeruginosa were employed for a combined pre-treatment of wastewater from poultry processing industry. During the hydrolysis step of the wastewater fat better results were obtained at 34°C with biosurfactant 0.4% (v/v) and liquid enzyme preparation 6.2% (v/v) or at 46°C with biosurfactant 0.1% (v/v) and liquid enzyme preparation 3.8% (v/v). The pre-hydrolysis in two different conditions of enzyme and biosurfactant concentrations at 34°C and posterior anaerobic treatment allowed the COD removal and methane production, while the no hydrolyzed wastewater besides the COD removal, did not show methane production. Those results suggest the importance and efficiency of the pre-treatment with home-made lipases and biosurfactant during the high fat content wastewater pre-treatment.

Biotechnological treatment of effluent from the combined enzymatic-ultrasound scouring of raw wool

New eco-labels for textile products and demands to wastewater discharges are forcing wool scouring processes to reuse wastewater and to search for more efficient and environmental friendly methods of processing. This challenge has prompted intensive research in new advanced treatment technologies. Due to the high level of detergent usage, the most widely used treatment of wool scouring effluent (WSE) is anaerobic. As the pressure to use more environmentally acceptable treatment methods increases there is the need to study alternative, biologically efficient treatment systems for WSE. This work aims at studying the influence of the combined enzymatic-ultrasound scouring of raw wool fibers on the effectiveness of the anaerobic treatment of effluents from this processing. Experiments carried out combined enzyme and ultrasound scouring of wool followed by treatment of effluents obtained. Aerobic and anaerobic treatments of these effluents were performed using a special laboratory reactor. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of effluents from different scouring processes were defined. The results of this study indicate that the anaerobic biological and chemical treatments of WSE treated by combined enzymatic-ultrasound scouring is a promising alternative technology from the point of view of reducing the wastewater pollution and the effective cleaning of effluents coming out from this process.

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.

Effect of temperature on two-phase anaerobic reactors treating slaughterhouse wastewater

The effectiveness of the anaerobic treatment of effluent from a swine and bovine slaughterhouse was assessed in two sets of two-phase anaerobic digesters, operated with or without temperature control. Set A, consisting of an acidogenic reactor with recirculation and an upflow biological filter as the methanogenic phase, was operated at room temperature, while set B, consisting of an acidogenic reactor without recirculation and an upflow biological filter as the methanogenic phase, was maintained at 32°C. The methanogenic reactors showed COD (Chemical Demand of Oxygen) removal above 60% for HRT (Hydraulic Retention Time) values of 20, 15, 10, 8, 6, 4, and 2 days. When the HRT value in those reactors was changed to 1 day, the COD percentage removal decreased to 50%. The temperature variations did not have harmful effects on the performance of reactors in set A.

Enzymatic pre-hydrolysis applied to the anaerobic treatment of effluents from poultry slaughterhouses

A pool of hydrolases with 21.4 U g −1 lipase activity was produced through solid-state fermentation of the fungus Penicillium restrictum in waste from the Orbignya oleifera (babassu) oil processing industry. Enzymatic hydrolysis and anaerobic biodegradability tests were conducted on poultry slaughterhouse effluents with varying oil and grease contents (150–1200 mg l −1) and solid enzymatic pool concentrations (0.1–1.0% w/v). Enhanced anaerobic treatment efficiency relative to raw effluent was achieved when a 0.1% concentration of enzymatic pool was used in the pre-hydrolysis stage with 1200 mg oil and grease l −1 (chemical oxygen demand (COD) removal efficiency of 85% vs. 53% and biogas production of 175 ml vs. 37 ml after 4 d).

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.

The Application of Anaerobic Wastewater Treatment System in Paper Industry

Since the beginning of the eighties, anaerobic effluent treatment plants have been applied in the paper industry. The UASB reactor has become the most popular reactor. It is operating on almost all types of paper industry effluents, but the largest numbers can be found in the paper recycling industry.When acid paper sizing was abandoned, circumstances for fresh water reduction improved considerably. so that process waters and resulting effluents became more concentrated in COD.Besides this, anaerobic plants have also become popular for the treatment of condensates from sulphite (SP) and sulphate (Kraft) mills as well as for TMP and CTMP effluents and even for black liquor from soda pulping and NSSC. Improvements to the conventional UASB reactor have further increased loading rates and reduced hydraulic retention times. The IC (Internal Circulation) UASB reactor can treat twice the COD loading of conventional UASB at hydraulic retention times of 2 hours or more and is replacing the role of UASB in the paper industry effluents.