Anaerobic Lagoon Research Articles

Field measurements of fugitive methane emissions from three Australian waste management and biogas facilities.

A key environmental sustainability requirement for the treatment of organic waste via anaerobic digestion (AD) is the prevention of unwanted methane emissions in the production chain whenever possible. Identifying and quantifying these emissions has been frequently investigated, particularly in Europe. However, the challenges of climate change are also becoming vitally important in Australia. This novel study presents the results from emission measurement campaigns carried out at two biogas plants and one landfill site in Australia. An on-site approach consisting of leakage detection and emission quantification by a static chamber method was applied. Twenty-nine leakages were detected predominantly on the digesters (gastight covered anaerobic lagoons) of the biogas plants. Ten emission hot spots were found on the surface cover of a landfill site. Methane emission rates of 9.9±2.3kgh-1 (10.5±2.4% CH4) for biogas plant A, 3.0±1.9kgh-1 (8.1±5.2% CH4) for biogas plant B and 41-211gh-1 for the two largest emission hot spots from the landfill were measured. Since not every single leakage or hot spot could be quantified separately, the stated overall emission rates had to be extrapolated. Importantly, the emission rates from the landfill should be interpreted carefully due to the limited overall area which could be practicably investigated. Leakages occurred at common components of the covered anaerobic lagoons such as the membrane fixation or concrete walls. Repairing these parts would increase the plant safety and mitigate negative environmental effects.

Sludge management in lagoons: The role of denitrification as a function of carbon biodegradation

Sludge from the bottom of an anaerobic lagoon storage system contains nutrient residues, as well as inorganic and organic matter. These wastes have polluting impacts on swine farms, and beyond the management alternatives, few studies apply economic and sustainable biological methods to reduce their effects. In this study, denitrification was proposed as an alternative sludge treatment for settling tanks (ST), biodigesters, and stabilized lagoons. The sludge sources had different deposition times and bioavailable carbon concentrations. Accordingly, the effects of agitation and carbon and nitrate concentrations were evaluated. The best removal feasibility was presented with the ST sludge, corresponding to 25% (v v−1) of the background volume, achieving higher total organic carbon (1342 mg L−1 day−1) and nitrate (279 mg L−1 day−1) removal. Furthermore, sludge management by denitrification was affected by carbon bioavailability and proven to be cost-effective, with 125 days required for processing.

Variation in hydrogen sulfide emissions from a U.S. Midwest anaerobic dairy lagoon.

Hydrogen sulfide (H2 S) emissions from midwestern United States dairy anaerobic waste lagoons are episodic and seasonal. Emissions were modeled using an inverse diffusion model in conjunction with measured concentrations and turbulence. The potential for lagoon mixing was estimated by the Brunt frequency using a theoretical Fourier series temperature profile model constructed from measured air and lagoon temperatures. Annual H2 S emissions from the dairy parlor and holding area liquid waste, based on 318 d of measurement, were 212g m-2 or 807g head of cattle-1 . Hydrogen sulfide emissions were highest in the spring and the fall. Eleven days with emissions >7g d-1 head-1 accounted for 25% of the annual emissions. Shear mixing appeared to dominate the mixing in the lagoon when the lagoon was estimated to be nearly isothermal. Wind shear correlated with significantly greater daily mean emissions. The H2 S emissions from this lagoon appeared to result from a series of processes; biogenic production of H2 S in the sludge, H2 S-enriched bubbles rise through the lagoon by buoyancy and wind shear induced mixing, and bubbles bursting at the surface either due to desiccation of the bubbles or surface disturbances induced by wind and precipitation.

Nutrients recovery from fresh liquid manure through an airlift reactor to mitigate the greenhouse gas emissions of open anaerobic lagoons

Open anaerobic lagoons are widely used for liquid manure storage and treatment, with excess greenhouse gas (GHG) and odor emissions. In this study, liquid manure was valorized through hybrid nitrogen and phosphorous recovery as value-added products using an airlift reactor. Also, the organic load of liquid manure was reduced before discharging into anaerobic lagoons, which simultaneously mitigated GHG emissions. The results showed that 14.5% of total nitrogen (TN) was recovered as ammonium sulfate, while 38.8% of TN and 79.3% of total phosphorus (TP) were recovered as phosphorus-rich sludge. After the pre-treatment in the reactor, the odor could be controlled effectively due to a 94.2% decrease in total VFAs. In addition, 59.0% of COD was removed, which decreased the theoretical modeled GHG emissions by 51.7% compared to the traditional direct discharging. The application is promising for upgrading anaerobic lagoons of liquid manure.

A Framework Based on Finite Element Method (FEM) for Modelling and Assessing the Affection of the Local Thermal Weather Factors on the Performance of Anaerobic Lagoons for the Natural Treatment of Swine Wastewater

Anaerobic lagoons are natural wastewater treatment systems suitable for swine farms in small communities due to its low operational and building costs, as well as for the environmental sustainability that these technologies enable. The local weather is one of the factors which greatly influences the efficiency of the organic matter degradation within anaerobic lagoons, since microbial growth is closely related to temperature. In this manuscript, we propose a mathematical model which involves the two-dimensional Stokes, advection–diffusion-reaction and heat transfer equations for an unstirred fluid flow. Furthermore, the Anaerobic Digestion Model No1 (ADM1), developed by the International Water Association (IWA), has been implemented in the model. The partial differential equations resulting from the model, which involve a large number of state variables that change according to the position and the time, are solved through the use of the Finite Element Method. The results of the simulations indicated that the methodology is capable of predicting reasonably well the steady-state of the concentrations for all processes that take place in the anaerobic digestion and for each one of the variables considered; cells, organic matter, nutrients, etc. In view of the results, it can be concluded that the model has significant potential for the design and the study of anaerobic cells’ behaviour within free flow systems.

Process Optimisation of Anaerobic Digestion Treating High-Strength Wastewater in the Australian Red Meat Processing Industry

This work represents and reviews a compilation of investigations into improving anaerobic digestion performance of high-strength wastewater in the Australian Red Meat Processing industry. The industry produces significant quantities of organic-rich wastewater which requires treatment prior to release to the environment. Anaerobic lagoons are a cost-effective method of waste treatment where land availability is not an issue; however, the high fat load in the wastewater can negatively impact the anaerobic lagoon system and result in compromised anaerobic digestion performance. This paper will discuss the importance of upstream primary pre-treatment and review a series of investigations focused on optimising digester performance and improving fat biodegradability. These studies include: 1. the effect of temperature and mixing; 2. the influence of feedstock trace element composition and supplementation, and; 3. the potential benefit from pre-treatments such as chemical, thermobaric, thermochemical and bio-surfactant. This paper discusses the implications of these findings for covered anaerobic lagoon operation and provides recommendations to promote optimum digester performance and future opportunities in adopting alternate anaerobic digestion technology options. Finally, the paper provides recent trends toward the use of other waste streams for co-digestion and discusses this in terms of digester optimization and technology options.

Quasi-Active Thermal Imaging of Large Floating Covers Using Ambient Solar Energy

Melbourne Water Corporation has two large anaerobic lagoons at the Western Treatment Plant (WTP), Werribee, Victoria, Australia. The lagoons are covered using numerous sheets of high-density polyethylene (HDPE) geomembranes to prevent the emission of odorous gases and to harness biogas as a source of renewable energy. Some of the content of raw sewage can accumulate and form into a solid mass (called “scum”). The development of a large body of solid scum that rises to the surface of the lagoon (called “scumbergs”) deforms the covers and may affect its structural integrity. Currently, there is no method able to effectively “see-through” the opaque covers to define the spread of the scum underneath the cover. Hence, this paper investigates a new quasi-active thermal imaging method that uses ambient solar radiation to determine the extent of the solid matter under the geomembrane. This method was devised by using infrared thermography and a pyranometer to constantly monitor the transient temperature response of the HDPE geomembrane using the time varying ambient solar radiation. Newton’s cooling law is implemented to define the resultant cooling constants. The results of laboratory-scale tests demonstrate the capability of the quasi-active thermography to identify the presence and the extent of solid matter under the cover. This paper demonstrates, experimentally, the importance of measuring the surface temperature of the cover and solar intensity profiles to obtain the cooling process when during variations in solar intensity during normal sunrise, sunset, daily transitioning from morning–afternoon–evening and cloud cover events. The timescale associated with these events are different and the results show that these daily transient temperature cycles of the geomembranes can be used to detect the extent of the accumulation of solid matter underneath the geomembrane. The conclusions from this work will be further developed for field trials to practically monitor the growth in the extent of the scum under the floating covers in WTP with the ambient solar energy.

Ammonia Emissions from Differing Manure Storage Facilities at Two Midwestern Free-Stall Dairies

Dairies contribute a major portion of agricultural ammonia emissions in the United States. Emissions were monitored over two years from an anaerobic lagoon receiving manure from cows in the milking parlor and holding area in Indiana (IN), USA and a storage basin receiving manure from cows in barns as well as the milking parlor and holding area in Wisconsin (WI), USA. Emissions were monitored using open-path tunable diode lasers, sonic anemometers, and two emission models. The mean annual daily emissions at the WI storage basins (30 µg m−2 s−1) was nearly equal to that at the IN lagoon (27 µg m−2 s−1). The mean annual daily ammonia (NH3) emissions on a per animal basis were greater at the WI basins (33 g NH3 hd−1 d−1; 26 g NH3 AU−1 d−1) (hd = animal; AU = 500 kg animal mass) than at the IN lagoon (9 g NH3 hd−1 d−1; 7 g NH3 AU−1 d−1). Emissions from both storage systems were highest in the summer, lowest in the winter, and similar during the spring and fall. Emissions were strongly correlated with air temperature and weakly correlated with wind conditions. Greater emissions at the WI basins appeared to be related primarily to the characteristics of the stored manure.

Oxygen Transfer Capacity as a Measure of Water Aeration by Floating Reed Plants: Initial Laboratory Studies

Reed-Phragmites australis (Cav.) Trin. ex Steud, an aquatic plant, commonly used in constructed wetlands for wastewater treatment, supplies oxygen into the subsurface environment. Reed may be used as a ‘green machine’ in the form of a floating vegetation cover with many applications: wastewater lagoons, manure lagoons or sewage sludge lagoons. An important measure of the performance of the plant system is the oxygen transfer capacity (OTC). Accurate prediction of the OTC in relation to reed biomass would be crucial in modelling its influence on organic matter degradation and ammonia–nitrogen oxygenation in such lagoons. Laboratory experiments aiming to determine OTC and its dependence on reed biomass were carried out. Eight plants with a total dry mass ranging from approximately 3 to 7 g were tested. Mean OTC was determined per plant: 0.18 ± 0.21 (g O2·m−3·h−1·plant−1), with respect to leaves-and-stem dry mass (dlsm): 44.91 ± 35.21 (g O2·m−3·h−1·g dlsm−1), and to total dry mass (dtm): 33.25 ± 27.97 (g O2·m−3·h−1·g dtm−1). In relation to the relatively small root dry mass (drm), the OTC value was 136.02 ± 147.19 (g O2·m−3·h−1·g drm−1). Measured OTC values varied widely between the individual plants (variation coefficient 115%), in accordance with their differing size. Oxygenation performance was greatest in the reed plants with larger above ground dry mass (>4 g dlsm), but no influence of the root dry mass on the OTC rate was found.

Biogas y compost a partir de residuos

El incremento de residuos asociados al crecimiento de la población es un problema grave en nuestra sociedad. La posibilidad de biometanización es una alternativa amigable con el medio ambiente ya que contribuye al procesamiento de centenares de toneladas de basura que se acumulan en nuestras ciudades. En Neuquén, la fracción orgánica de los residuos alcanza el 44 % y es una potencial fuente de energía. Este puede ser valorizado por medio de biogas y compost.El potencial metanogénico se puede medir empleando el método de la jeringa que tiene la ventaja de ser un procedimiento experimental de bajo costo. El presente trabajo consistió en comparar la cantidad de biogas generada en función de la concentración de sólidos totales. El potencial de biogas es el volumen de producto generado por la cantidad de sustrato, en este caso, la fracción orgánica de los residuos. Se realizó el ensayo usandolo como sustrato y empleando el agua residual de laguna anaerobia como inóculo. Se utilizó jeringas de 60 ml a 35 °C con concentraciones sustrato 5 %, 10 %, 15 %, 20 % y 40 % de sólidos totales de la fracción orgánica y 10 ml de inóculo de agua residual de laguna anaerobia. Se determinó que la condición más favorable fue para las concentraciones de 5 % y 20 % de sólidos totales. Además, se evaluó la preparación de un acelerante para el digestato por el método de zucconi.

Performance evaluation and sustainable, cost-effective and energy-efficient process enhancement measures for Pagla sewage treatment plant, Bangladesh

At present, Pagla Sewage Treatment Plant (STP) is the only sewage treatment plant in Dhaka, the capital city of Bangladesh, with a capacity to treat 120 million litres per day (MLD) of sewage. Evidence suggests that the plant is overburdened and cannot by itself handle the wastewater generated in Dhaka. Furthermore, the treatment plant is hampered by a number of functional problems which limit both its capacity to treat wastewater, and the efficiency of the treatment process. Rectifying the functional problems of the plant and implementing enhancement measures would greatly improve the functionality of Pagla STP. A thorough evaluation was carried out on the performance of the plant and a detailed process flow diagram developed. Several functional problems were identified, mostly pertaining to the primary sedimentation tanks and the unused sludge lagoons. The influent and effluent characteristics of Pagla STP were also assessed using BOD5 values as the primary criteria. It was found that the influent BOD5 value was 832 mg/L and effluent BOD5 was 497.5 mg/L, against design values of 120 mg/L and 50 mg/L respectively. Based on the evaluation, theoretical analysis was done, and a sustainable, cost and energy efficient retrofit was proposed whereby the sludge lagoons would be converted to anaerobic lagoons to facilitate biological pretreatment. It is estimated that implementing such an enhancement would increase the treatment capacity of the plant beyond its original design. Furthermore, theoretical calculations show up to 5,000 m3 of methane gas can be generated daily from the plant, which is enough to power 6,000 homes with renewable energy.

Strain Monitoring Strategy of Deformed Membrane Cover Using Unmanned Aerial Vehicle-Assisted 3D Photogrammetry

Large structures and high-value assets require inspection and integrity assessment methodologies that ensure maximum availability and operational capabilities. Large membranes are used as floating covers at the anaerobic wastewater lagoons of Melbourne Water’s Western Treatment Plant (WTP). A critical function of this high-value asset pertains to the harnessing of the biogas gas generated at these lagoons as well as protecting the environment from the release of odours and greenhouse gases. Therefore, a proactive inspection and efficient management strategy are required to ensure these expensive covers’ integrity and continued operation. Not only is identifying the state of stress on the floating cover crucial for its structural integrity assessment, but the development of rapid and non-contact inspections will significantly assist in determining the “real-life” performance of the cover for superior maintenance management. This study investigates a strain determination method for WTP floating cover which integrates unmanned aerial vehicle (UAV)-assisted photogrammetry with finite element analyses to determine the structural integrity of these covers. Collective aerial images were compiled to form 3D digital models of the deformed cover specimens, which were then employed in computational and statistical analyses to assess and predict the strain of the cover. The findings complement the future implementation of UAV-assisted aerial photogrammetry for structural health assessment of the large floating covers.

Uncertainty in using dispersion models to estimate methane emissions from manure lagoons in dairies

Manure lagoons in dairies make significant contributions to emissions of methane, a major greenhouse gas; however, there is a high level of uncertainty in these emissions. In this paper, we apply dispersion models in combination with a unique sampling strategy, which involves stationary measurements at multiple points around the lagoons to estimate methane emissions from manure lagoons located in two dairies, one in Southern California and the other in Central California. We then estimate the uncertainty associated with the results from this approach by interpreting our measurements with two dispersion models, a numerical Eulerian model (EN) and a backward Lagrangian stochastic (bLS) model. The range of emissions inferred from these two models is a measure of uncertainty related to differences in the formulation of these models. We also estimate 95% confidence intervals for the emission estimates from each of the models by bootstrapping the residuals between model estimates and measurements. Both models explain more than 85% of the variance of the methane concentrations measured at the two dairies. For the Southern California dairy (1066 milking cows), the 95% confidence interval of the emission rate inferred by the EN model is 282 kg/d to 482 kg/d. The corresponding interval for the bLS model is 174 kg/d to 246 kg/d. The best fit value from the EN model is about 1.9 times that from the bLS model. For the Central California dairy (3200 milking cows), the best emission rates from the two models differ by about 10%. The emission rate inferred by the EN model ranges from 3198 kg/d to 5312 kg/d, and that from the bLS ranges from 2943 kg/d to 4977 kg/d. Our results are consistent with methane emissions derived from information on dairy cow population and manure management practices at these two dairies. These results suggest this measurement technique is easily deployed and effective at quantifying uncertainties associated with methane emissions from manure lagoons.

Remote Monitoring of Floating Covers Using UAV Photogrammetry

High-density polyethylene (HDPE) is commonly the material of choice for covered anaerobic lagoons (CAL) at wastewater treatment plants. The membrane floats on the wastewater, and hence is called a “floating cover”, and is used for odour control and to harvest the methane-rich biogas as a renewable resource to generate electricity. The floating cover is an expensive and high-value asset that demands an efficient methodology for the determination of a set of engineering quantities for structural integrity assessment. Given the dynamics of the anaerobic activities under the floating cover, the state of deformation of the floating cover is an engineering measurand that is useful for its structural health assessment. A non-contact measurement strategy is preferred as it offers practical and safety-related benefits over other methods. In collaboration with Melbourne Water Corporation (MWC), an unmanned aerial vehicle (UAV) assisted photogrammetry approach was developed to address this need. Following the definition of the appropriate flight parameters required to quantify the state of deformation of the cover, a series of periodic flights were operated over the very large floating covers at MWC’s Western Treatment Plant (WTP) at Werribee, Victoria, Australia. This paper aims to demonstrate the effectiveness and practicality of this inspection technique to determine the state of deformation of the floating covers measured over a ten-month period.

Diversity of anoxygenic phototrophic bacteria in anaerobic lagoons and facultative stabilization pond used in treatment of sewage

The objective of this study was to identify the anoxygenic phototrophic bacteria in the anaerobic lagoons and facultative stabilization pond of the Vale do Ribeira, Cajati, Sao Paulo, Brazil, and their correlation with physical and chemical parameters of the ponds’ water. The samples were collected seasonally (spring, summer, autumn and winter) in the sub-surface, intermediate layer and sediment-water interface. We used the PCR/DGGE with puf M 557FGC and puf M 750R primers specific to the reaction center of the photosynthetic phototrophic bacteria for their identification. The amplification products were separated by electrophoresis on denaturing gradient gel. From the bands cut out and sequenced from DGGE, the identified bacteria were Rhodopseudomonas palustris (99% similarity), Chromatium sp . (92%), Thiocapsa sp. (90%), Rhodospirillum sp. (95%), Roseobacter sp. (93%) and other uncultured bacteria.

Application of a mathematical model to predict simultaneous reactions in anaerobic plug-flow reactors as a primary treatment for constructed wetlands

Anaerobic digestion technologies offer a set of advantages when they are implemented as a primary treatment phase prior to the use of constructed wetland systems in low cost wastewater facilities. The aim of this study is to describe a model capable of reflecting the complex functioning of anaerobic lagoons, subject to continuous flux in the feed pipe, taking into account that physicochemical properties are subject to a concentration gradient and biochemical ones to simultaneous reactions which depend on each other. Based on both Stokes and advection-diffusion-reaction equations, the proposed model includes twenty-one variables to describe hydraulic, physical, biochemical and physicochemical characteristics that take place in different points of the system and at different moments of time. Drawn up by the International Water Association, the anaerobic digestion model ADM1 is included for the purpose of incorporating the anaerobic processes in the calculation. The finite element method was used to solve the nonlinear, second order partial differential equations of the model. The calculation strategy was designed using a flowchart. Using the open-source FreeFem++ software, a simulation of the mathematical model, in bi-dimensional space, is presented to demonstrate the dynamic behaviour of the proposed model. This yields essential information about the performance of the substrate, cells, and the biochemical reaction products in each of the points within the reactor. Simulations show the potential of this methodology to carry out studies of the behaviour of each of the variables contemplated in the model, as well as comparative studies of the various possible options. In addition, this methodology can be used to help modify the behaviour of the variables based on digester geometry and the boundary values the system is subject to. From the results, it can be concluded that the proposed methodology can be a useful tool for calculating and designing the aforementioned synergistic systems of anaerobic digester plug-flow reactors and constructed wetlands.

Hybrid Upflow-Anaerobic Filter (HU-AF) Integrated technology for bio-methane generation from vinasse with shorter hydraulic retention time

Research about Hybrid Upflow-Anaerobic Filter (HU-AF) integrated technology for bioenergy generation from vinasse was conducted. Modification of influent flow system, expansion of filter contact area and addition of gas accumulator for biogas collection were used to enhance the degree of vinasse biodegradation biogas generation, and yet to shorten the hydraulic retention time (HRT). Hybrid Upflow-Anaerobic Filter (HU-AF) integrated technology was a double dome reactor with sequential connection, with up-flow inlet distribution inside the reactor. Total volume of HU-AF was 60 m3. A mixing and a feeding chamber, with volume 3 m3, each were installed before HU-AF reactor. A reservoir chamber with volume of 6 m3 was added after HU-AF reactor. OLR was 2.04 kg COD/day. A methanogenic seed sludge derived from anaerobic lagoon. The experiment was carried out initially by seeding, acclimatization and adaptation of microorganisms inside the reactor. A feeding ratio of vinasse: water = 1:4, and initial pH of 6 were adjusted. Result showed that Full-scale HU-AF integrated technology was able to degrade COD with maximum degradation of COD 55.45% at pH 7.1, and shorten the HRT into 32 days. Biogas production was consisted of 57.21 % methane, 13.98% CO2 and various gases 28.1% (H2S, VOC, CO and H2O). This experiment showed that HRT was shorter than conventional reactor.

Bacterial community structures and biodegradation kinetic of Tiamulin antibiotic degrading enriched consortia from swine wastewater

The antibiotic tiamulin (TIA) is common and widely used medication for dysentery eradication in swine productions. Tiamulin persists in livestock manure, and its residues have been found in various environment. This work obtained four tiamulin-degrading enriched bacterial consortia from a covered anaerobic lagoon system and a stabilized pond system of swine farms. Tiamulin was efficiently removed by the enriched cultures at the concentrations between 2.5 and 200mg/L, with a removal of 60.1-99.9% during 16h and a degradation half-life of 4.5-15.7h. The stabilized pond system cultured with taimulin solely could eliminate tiamulin at the highest rates. The logistic substrate degradation model fit most of the experimental data. Next-generation amplicon sequencing was conducted, and it was found that the bacterial community was significantly impacted by the inoculum source, nutrient addition, and high tiamulin concentrations. Principal coordinate analysis (PCoA) indicated the similarity of bacterial communities in the original enriched samples and the 2.5mg/L tiamulin-removed cultures. The 200mg/L consortia were rather different and became similar to the other 200mg/L consortia from different sources and cultures without nutrient supplementation. Shannon and Simpson indices suggested a reduction in bacterial diversity at high concentrations. The microbes that had high growth in the most efficient enriched culture, or which were abundant in all samples, or which increased with higher tiamulin concentrations were likely to be the major tiamulin-degrading bacteria. This is the first report suggested the possible roles of Achromobacter, Delftia, Flavobacterium, Pseudomonas, and Stenotrophomonas in tiamulin degradation.

Insight into the structural configuration of metagenomically derived lipase from diverse extreme environment

The present study aims at finding the structural similarity of five metagenomically derived lipase protein sequences from diverse extreme environmental conditions i.e. hot springs, low-temperature regions, anaerobic lagoons and marine source. Using PROTPARAM server, the analysis of physicochemical characteristics of all lipases were found to be neutral in pH and are hydrophilic in nature except clone RK-Lip-479 and clone JKP01. The molecular weight varied from 31.2 kDa to 46.4 kDa while amino acid residues varied from 293 (clone FosC12) to 417 (clone JKP01). The instability index of all the proteins ranged from 22 to 35, which indicate their stability under given conditions except clone h1Lip1 lipase with higher instability index of 44.72 indicating less stable. Determination of the secondary structure of all proteins by SOPMA tool revealed the dominance of α-helices ranging between 27.34% (clone h1Lip1 lipase) to 45.05% (clone FosC12 lipase) and coils ranged between 27.3% (clone FosC12 lipase) to 34.53% (clone JKP01 lipase). 3D structures of all lipase proteins deduced using SWISS-MODEL automated server were found to be monomeric. The structures were retrieved and visualized using PyMol v0.99. The QMEAN values were within the range of 0.8–1.5 suggesting the models to be of suitable. The outcome of RAMPAGE and VERIFY3D servers for the models obtained were also observed to be of much suitable. The insight into the structural configurations of proteins revealed as above may help in varied applicability of metagenomics lipases.

Case study on the effect continuous CO2 enrichment, via biogas scrubbing, has on biomass production and wastewater treatment in a high rate algal pond

Microalgae grown in high rate algal ponds (HRAP) treating wastewater are considered a promising feed for biofuel production. Biomass productivity is often considered to be limited by carbon availability, with the addition of CO2 being the proposed solution. Biogas from anaerobic wastewater treatment potentially provides a cheap, co-located CO2 source. Two identical 223 m2 HRAPs were constructed at Melbourne Water's Western Treatment Plant, where biogas from an anaerobic lagoon is used to generate electricity. One HRAP was fed secondary treated wastewater that had been enriched with CO2 recovered from the biogas using industry standard biogas scrubbers, the Enriched HRAP, while the other HRAP was fed the same wastewater expect it had by passed the biogas scrubbers, the Control HRAP. The biomass production and wastewater treatment performance of the two HRAPs was compared over 12 months. The inlet to the Enriched HRAP had significantly higher free CO2 and inorganic carbon, 175.00 ± 49.30 mg L−1 and 110.00 ± 10.2 mg L−1, than the inlet to the Control HRAP, 9.30 ± 7.08 mg L−1 and 89.62 ± 5.12 mg L−1. There were no significant differences in biomass production between the HRAPs as measured by dry matter, particulate organic carbon or nitrogen. Chlorophyll a was statistically higher in the Enriched HRAP, however, this measurement is potentially unreliable. Regarding wastewater treatment, only total nitrogen and ammonium removal differed significantly between the HRAPs, with the Control HRAP, 59.13 ± 21.13% and 76.46 ± 32.33%, slightly outperforming the Enriched HRAP, 53.52 ± 17.41% and 68.76 ± 31.17%. Overall, neither biomass production nor wastewater treatment was meaningfully improved by CO2 enrichment, however, wastewater treatment was still effective in both HRAPs.