Pilot-scale Conditions Research Articles

ENHANCED REMOVAL OF ORGANIC MATTER AND NUTRIENTS BY SEQUENTIAL BATCH REACTORS

The aim of this research was to improve the removal of organic matter and nutrients from wastewater from pig farms in a combined batch reactor performed as anaerobic-aerobic sequential. For this purpose, it was suggested to include recirculation cycles of wastewater in a sequentially pulsed manner in the anaerobic treatment followed by intermittent aeration in the aerobic-anoxic treatment. This novelty implemented in both sequential reactors was studied under pilot scale conditions. The process of pulsed intermittent recirculation allowed better contact between the microorganisms and organic matter, and intermittent aeration improved the removal of nutrients, primarily nitrogen (nitrification and denitrification), total phosphorous and organic matter. The best configuration tested for the combined system was the one consisting of pulsed intermittent recirculation with 1 hour of recirculation and 3 hours rest in the anaerobic step and 2 hours of aeration and 1 hour without aeration cycle in the aerobic step. The removals achieved were 98 1% of total organic matter, 86 5% of soluble organic matter, 96 1% of total phosphorus and 55 18% of total nitrogen. Hence, it was demonstrated that a combined system with pulsed intermittent recirculation in the anaerobic stage and intermittent aeration in the aerobic stage could enhance the overall treatment of swine wastewater.

Factors contributing to bacteria inactivation in the Galdieria sulphuraria-based wastewater treatment system

Our previous pilot scale studies showed concurrent removals of biochemical oxygen demand and nutrients, and inactivation of pathogens in urban wastewaters by an extremophilic alga, Galdieria sulphuraria. The current work evaluated the following as potential factors contributing to the observed pathogen inactivation, using E. coli as a surrogate: bacterial toxicity of algal metabolites, culture pH and temperature, sunlight, dissolved oxygen and adsorption to algal biomass. Microtox toxicity results implied that algal metabolites were free of bacterial toxicants as the toxicity in the reactor decreased from 38.8% to zero in 4 days. Low cultivation pH of 4 was identified as the primary factor influencing E. coli reductions. At neutral pH, under sunlight, E. coli were reduced to undetectable levels in 24 h. But, in the presence of live algal biomass and sunlight, E. coli were reduced to undetectable levels within 12 h. We attribute this accelerated reduction of E. coli to the synergistic effect of sunlight and elevated dissolved oxygen levels generated by biomass in the reactor. Temperatures below 45 °C and adsorption of bacteria to algal biomass did not appear to cause inactivation of E. coli. Simulation of pilot-scale conditions confirmed that the synergistic effects of pH, sunlight, algal biomass, and dissolved oxygen contributed to the superior fecal coliform inactivation observed in the algal wastewater treatment system.

Technical feasibility and carbon footprint of biochar co-production with tomato plant residue

World tomato production is in the increase, generating large amounts of organic agricultural waste, which are currently incinerated or composted, releasing CO2 into the atmosphere. Organic waste is not only produced from conventional but also urban agricultural practices due recently gained popularity. An alternative to current waste management practices and carbon sequestration opportunity is the production of biochar (thermally converted biomass) from tomato plant residues and use as a soil amendment.To address the real contribution of biochar for greenhouse gas mitigation, it is necessary to assess the whole life cycle from the production of the tomato biomass feedstock to the actual distribution and utilisation of the biochar produced in a regional context. This study is the first step to determine the technical and environmental potential of producing biochar from tomato plant (Solanum lycopersicum arawak variety) waste biomass and utilisation as a soil amendment.The study includes the characterisation of tomato plant residue as biochar feedstock (cellulose, hemicellulose, lignin and metal content); feedstock thermal stability; and the carbon footprint of biochar production under urban agriculture at pilot and small-scale plant, and conventional agriculture at large-scale plant.Tomato plant residue is a potentially suitable biochar feedstock under current European Certification based on its lignin content (19.7%) and low metal concentration. Biomass conversion yields of over 40%, 50% carbon stabilization and low pyrolysis temperature conditions (350–400°C) would be required for biochar production to sequester carbon under urban pilot scale conditions; while large-scale biochar production from conventional agricultural practices have not the potential to sequestrate carbon because its logistics, which could be improved. Therefore, the diversion of tomato biomass waste residue from incineration or composting to biochar production for use as a soil amendment would environmentally be beneficial, but only if high biochar yields could be produced.

Treatment of water contaminated by volatile organic compounds in hydroponic root mats

Hydroponic root mats (HRMs) are relatively new ecological water treatment technology with the aquatic vegetation forming buoyant root mats by their dense interwoven roots and rhizomes, either floating or sitting on the bottom of the water body. The aim of this study was to investigate the treatment of water contaminated by volatile organic compounds (VOCs) in HRMs under pilot-scale conditions. Floating hydroponic root mats (FHRM) and a hydroponic root mat filter (HRMF) mesocosms were established near a former industrial area in Leuna. The mesocosms received the contaminated groundwater with the main VOCs were benzene and methyl tert-butyl ether (MTBE). The results revealed that both systems exhibited a similar removal performance of MTBE during the two years operation. Seasonal variation was observed for benzene removal in both systems, with almost complete removal of benzene during summer period. The FHRM system exhibited higher benzene removal efficiency than the HRMF system, especially during the second year of operation. MTBE is more difficult to be removed than benzene in both systems, with overall MTBE mean removal efficiency of 32% as compare to 61% for benzene removal. Both benzene and MTBE removals are shown to be positively correlated with water loss in both systems, while air temperature only had significant influence on VOCs removal in the HRMF system. The emission rates of benzene and MTBE in the FHRM system are 8.4 and 6.9mgm−2 d−1, respectively. This removal accounted for 3.0% and 30.8% of the total benzene and MTBE removal. The emission rates of benzene and MTBE in the HRMF system were 6.0 and 1.4mgm−2 d−1, respectively, accounting for 2.3% and 8.3% of total removal of benzene and MTBE. In conclusion, HRMs can be an efficient approach to treat water contaminated by benzene in summer time, and the volatilization of benzene will decrease in the HRMs with the development of the root mat.

Comparing targeted and non-targeted high-resolution mass spectrometric approaches for assessing advanced oxidation reactor performance

High resolution mass spectrometry (HR-MS) offers the opportunity to track large numbers of non-target analytes through water treatment processes, providing a more comprehensive view of reactor performance than targeted evaluation. Both approaches were used to evaluate the performance of a pilot scale advanced oxidation process (AOP) employing ultraviolet light and hydrogen peroxide (UV/H2O2) to treat municipal wastewater effluent. Twelve pharmaceuticals and personal care products were selected as target compounds and added to reactor influent. Target compound removal over a range of flow rates and hydrogen peroxide addition levels was assessed using a liquid chromatograph combined with a quadrupole time-of-flight mass spectrometer (LC-qTOF-MS). Target compound removals were used to determine hydroxyl radical concentrations and UV fluence under pilot scale conditions. The experiments were also analyzed using a nontarget approach, which identified “molecular features” in either reactor influent or effluent. Strong correlation (r = 0.94) was observed between target compound removals calculated using the targeted and non-targeted approaches across the range of reactor conditions tested. The two approaches also produced consistent rankings of the performance of the various reactor operating conditions, although the distribution of compound removal efficiencies was usually less favorable with the broader, nontarget approach. For example, in the UV only treatment 8.3% of target compounds and 2.2% of non-target compounds exhibited removals above 50%, while 100% of target compounds and 74% of non-target compounds exhibited removals above 50% in the best condition tested. These results suggest that HR-MS methods can provide more holistic evaluation of reactor performance, and may reduce biases caused by selection of a limited number of target compounds. HR-MS methods also offer insights into the composition of poorly removed compounds and the formation of transformation products, which were widely detected.

Pilot-scale verification of maximum tolerable hydrodynamic stress for mammalian cell culture.

Although several scaling bioreactor models of mammalian cell cultures are suggested and described in the literature, they mostly lack a significant validation at pilot or manufacturing scale. The aim of this study is to validate an oscillating hydrodynamic stress loop system developed earlier by our group for the evaluation of the maximum operating range for stirring, based on a maximum tolerable hydrodynamic stress. A 300-L pilot-scale bioreactor for cultivation of a Sp2/0 cell line was used for this purpose. Prior to cultivations, a stress-sensitive particulate system was applied to determine the stress values generated by stirring and sparging. Pilot-scale data, collected from 7- to 28-Pa maximum stress conditions, were compared with data from classical 3-L cultivations and cultivations from the oscillating stress loop system. Results for the growth behavior, analyzed metabolites, productivity, and product quality showed a dependency on the different environmental stress conditions but not on reactor size. Pilot-scale conditions were very similar to those generated in the oscillating stress loop model confirming its predictive capability, including conditions at the edge of failure.

Bioremediation of TNT contaminated soil with fungi under laboratory and pilot scale conditions

Bioremediation of contaminated soil involves the utilization of innovative technology such as mycoremediation. The capability of fungi to grow in 2,4,6-trinitrotoluene (TNT) contaminated soil, to produce lignin modifying enzymes and to degrade TNT in soil was studied. White-rot fungi, namely Gymnopilus luteofolius, Kuehneromyces mutabilis, and Phanerochaete velutina, were incubated with TNT contaminated non-sterile soil (1000 mg kg−1). All the fungi produced high amounts of manganese peroxidase (MnP) in TNT contaminated soil, but no laccase. The most efficient fungus, P. velutina, degraded 80% of TNT in 2.5 months and was selected for further scale-up experiment with 0.3 t (0.56 m3) of soil and inoculum soil ratio of 1:30. The degradation of TNT was 70% in 49 days, and production of fungal metabolites, namely 4-amino-2,6-diaminotoluene and 2-amino-4,6-diaminotoluene was only 1% of the original TNT concentration. These metabolites were degraded to less than 0.5% during the following 58 days incubation. Fungal remediation process was scaled-up with P. velutina, which tolerated high concentration of TNT and was able to invade the whole mass of soil with only 10 kg of fungal inoculum growing on pine bark. With these parameters the process should be easy to scale-up for soil treatment in field.

P‐65: Advanced Processing of ITO and IZO Thin Films on Flexible Glass

Ultra‐thin 100µm thick flexible glasses with a maximum dimension of 250×300 mm2 were deposited with transparent conductive ITO and IZO using in‐line magnetron sputtering under pilot scale conditions. The flexible glass was coated at room temperature with ITO and IZO and further refined by dynamic flash lamp annealing (FLA) in the millisecond range. After flashing the films, we achieved an improved transmittance and a reduced sheet resistance of the films.

Accumulation of Chemical Oxygen Demand in Membrane Bioreactors at Pilot-Scale and Full-Scale Conditions

AbstractThe accumulation of high-molecular-weight organic compounds is a common phenomenon in membrane bioreactors (MBRs). It is currently not known to what extent accumulation occurs in full-scale plants because relevant tests were mostly performed in experimental plants. To overcome the lack of practical experience, a measurement campaign was carried out including four municipal wastewater treatment plants and two pilot plants [one MBR and one conventional wastewater treatment plant (WWTP)]. The results clearly showed that accumulation depends on sludge retention time (SRT), temperature, sludge volume index (SVI), and the fraction of volatile suspended solids (VSS). As a result of biological processes, the chemical oxygen demand (COD) accumulation may increase for a limited period of time and amounts 10–120 mg/(PE·d). The introduction of sludge from a municipal MBR into the system of conventional activated sludge plants (CAS) for external sludge handling does not affect the treatment efficacy of the la...

Comparative Metabolomic Study of Penicillium chrysogenum During Pilot and Industrial Penicillin Fermentations

Comparative metabolomics was carried out to investigate the metabolic differences of Penicillium chrysogenum in the pilot and industrial fermentations that resulted from the scale-up. By principal component analysis, the early stages of two fermentation processes were clearly distinguished, whereas the middle and final stages were clustered together. It indicated that the different metabolisms of cells in the pilot and industrial fermentations mainly existed during the early stage. Furthermore, the levels of polyamines, polyols, glycolysis, and tricarboxylic acid cycle intermediates, which changed more dramatically during the pilot process, were all higher in the pilot than in the industrial fermentation during the early stage. This indicated that the fermentation conditions of the early stage should be the focus of process management which is aimed at increasing penicillin production. Additionally, the comparative accumulations of the precursors of penicillin (valine, cysteine, and lysine) revealed that penicillin biosynthesis in the industrial process was more affected during the middle stage of fermentation. These findings provide new insights to further regulate the industrial process and improve the production of penicillin. More generally, this study attempts to address the scarcity of studies that contrast the metabolic outcomes between commercial- and pilot-scale conditions.

Microbiological and Physicochemical Characterization of Small-Scale Cocoa Fermentations and Screening of Yeast and Bacterial Strains To Develop a Defined Starter Culture

Spontaneous cocoa bean fermentations performed under bench- and pilot-scale conditions were studied using an integrated microbiological approach with culture-dependent and culture-independent techniques, as well as analyses of target metabolites from both cocoa pulp and cotyledons. Both fermentation ecosystems reached equilibrium through a two-phase process, starting with the simultaneous growth of the yeasts (with Saccharomyces cerevisiae as the dominant species) and lactic acid bacteria (LAB) (Lactobacillus fermentum and Lactobacillus plantarum were the dominant species), which were gradually replaced by the acetic acid bacteria (AAB) (Acetobacter tropicalis was the dominant species). In both processes, a sequence of substrate consumption (sucrose, glucose, fructose, and citric acid) and metabolite production kinetics (ethanol, lactic acid, and acetic acid) similar to that of previous, larger-scale fermentation experiments was observed. The technological potential of yeast, LAB, and AAB isolates was evaluated using a polyphasic study that included the measurement of stress-tolerant growth and fermentation kinetic parameters in cocoa pulp media. Overall, strains L. fermentum UFLA CHBE8.12 (citric acid fermenting, lactic acid producing, and tolerant to heat, acid, lactic acid, and ethanol), S. cerevisiae UFLA CHYC7.04 (ethanol producing and tolerant to acid, heat, and ethanol), and Acetobacter tropicalis UFLA CHBE16.01 (ethanol and lactic acid oxidizing, acetic acid producing, and tolerant to acid, heat, acetic acid, and ethanol) were selected to form a cocktail starter culture that should lead to better-controlled and more-reliable cocoa bean fermentation processes.

Linking laboratory data with pilot scale entrained flow coal gasification performance. Part 2: Pilot scale testing

By exploring the links between laboratory-scale gasification data (e.g. slag viscosity measurements, char reactivity considerations) and the performance of the same coals under realistic pilot-scale conditions, we are provided with a dataset that allow us to refine coal test procedures for entrained flow gasification, understand the entrained flow gasification process in significantly more detail than previously, and gain some new insight into how coal reactivity and slag viscosity properties interact to define operating envelopes for specific gasification technologies. The first paper in this two-part series presented a detailed characterisation of a suite of Australian coals using laboratory-scale gasification facilities. This paper presents gasification data obtained from pilot-scale testing of these same coals, and explores the links between laboratory data, coal assessments made using these data, and the performance of the coals under realistic conditions. The results demonstrate a high degree of consistency between laboratory indications of coal reactivity and coal gasification behaviour at pilot scale. This work also demonstrates the impact of interactions between coal conversion properties and slag formation and flow behaviour, and how these interactions dictate operational parameters for the gasifier.

Parameter and State Estimation of an Anaerobic Digestion Model in Laboratory and Pilot-Scale Conditions

AbstractThis work considers the parameter and state estimation of a low-order model of anaerobic digestion of cattle dung. First, on the basis of a previously identified parameter set, partial parameter estimation with laboratory experimental data is performed. A modern numerical sensitivity analysis, to our knowledge not used for microbial biotechnology models so far, is a successful part of the estimation procedure. Second, the estimation results are validated with pilot-scale experimental data and can be considered satisfactory. Third, state estimation of the main AD variables is made via H-infinity filtering.

Laboratory Studies of Producing Hydrogen and Incremental Oil From Light Oil Reservoirs Using Downhole Gasification

Abstract The idea of gasifying (reforming) a fraction of a light crude oil in the reservoir, was conceived originally by Davidson and Yule(1). This involved "stringing?? a series of downhole gasification (DHG) units along either a horizontal producer well or vertical producer well, or along some other suitable well arrangement. Although catalytic steam reforming of naphtha practiced on a large scale has been extensively researched, such understanding is largely restricted to much lower pressures than those investigated in the present study. We present results obtained using a small, "pilot-scale?? DHG unit, or reforming reactor, operated at up to 100 bar pressure. The feed to this unit was a light naphtha fraction cut from Statfjord crude oil. The effect of pressure, catalyst loading, steam to hydrocarbon ratio and gasifier temperature were investigated. Essentially, the conversion to inert gases, principally hydrogen and carbon dioxide, at high pressure was sufficiently high to make the process technically feasible in depleted light oil reservoirs. Furthermore, the economics of this novel enhanced oil recovery process, which also produces (and stores) hydrogen, appear to be very favourable. However, the experiments, which were conducted under pilot-scale conditions using a single-tube reactor unit, were not of sufficient duration time to test the long-term effects on catalyst activity owing to carbon fouling and sulphur poisoning. These factors (at least carbon deposition) can be controlled as demonstrated in the experiments by adjusting the steam-to-hydrocarbon ratio and the depth of naphtha-cut taken from the crude oil. These aspects of the process are to be further investigated in a Phase 2 project. Introduction Davidson and Yule(1) originally conceived the idea of a self-contained, downhole gasification (DHG) unit as a safer, "greener?? method for transporting oil out of environmentally sensitive areas, such as the Everglades, as gas. Subsequently, the focus was directed towards applying DHG in depleted light oil reservoirs. The inert gases generated by a downhole DHG unit(s) are directed into a gas cap, or used to create a gas cap (Figure 1). This would then allow gravity stabilized displacement (GSGI), WAG, or another assisted gas injection technique, to be implemented for the purpose of improved oil recovery. This is still a high priority, especially in such areas as the North Sea, and the many hundreds of depleted light oil fields in the US, where output continues to fall. The main IOR problem is the availability of a suitable gas to inject into the reservoir, especially offshore. Although the displacement dynamics are likely to be complex because of the hydrogen in the generated gas, it is estimated that valuable incremental oil can be gained using the DHG process.

Deoxynivalenol and other Fusarium mycotoxins in bread, cake, and biscuits produced from UK-grown wheat under commercial and pilot scale conditions

Bread, cakes and biscuits were manufactured from flour containing deoxynivalenol (DON) and low concentrations of zearalenone (ZON) and nivalenol (NIV). The results show that these mycotoxins remain mostly unaffected during manufacture. Although the results indicate that the mycotoxins are largely stable and survive processing, when concentrations were determined on an ‘as is’ basis as stipulated in legislation, levels in finished products were usually lower than in the starting flour due to the dilution effect of other ingredients such as fat, sugar and water. Thus mean concentrations of DON in bread were reduced by about 35% and 39% in white and wholemeal bread respectively which are in close agreement with the reduction required by the regulations although the changes that occur during milling white and wholemeal flour from whole wheat also need to be taken into account. The reduction of DON during cake manufacture is greater than for bread because flour makes up only about 25% of the starting ingredients. However, in biscuit production, particularly for crackers for which flour constitutes about 90% of the recipe ingredients, the reduction indicated by the regulations is not achieved. It is concluded that for some commercial processes, the whole-wheat or flour ingredients used will need to contain DON levels lower than those set by legislation to ensure that the final products will still meet statutory limits. Limited results with consignments containing low concentrations of ZON and NIV suggest that their stability and survival are similar to those for DON.

A pilot-scale study on ultraviolet disinfection system for drinking water

In recent years, ultraviolet technology for drinking water disinfection has experienced rapid growth in North America and Europe, driven by the needs of disinfection by-product reduction and control of emerging pathogens such as Cryptosporidium which are resistant to chlorination. Tsinghua University has performed some work based on a pilot-scale UV system in Dongguan. The aim of this study was to evaluate the efficacy of UV systems for drinking water under pilot-scale conditions (continuous flow system) and to compare with the collimated-beam results in the laboratory for the same water quality. The experiment results showed that (1) UV was effective against E. coli and TBC. B. substilis and MS2 were more UV-resistant, especially when UVT was below 90%. (2) The inactivation of micro-organisms by UV could be described by first-order kinetics using fluence–inactivation data from laboratory studies in CB tests for a certain fluence range. No inactivation at low fluences (shoulder) and no further increase of inactivation at higher fluences (tailing) was observed for some challenge micro-organisms. (3) Water quality and UV sensitivity of the micro-organism influenced the inactivation rate. (4) For the daily monitor results of 13,000 h, UV could be a stable disinfection manner for total coliform and TBC. (5) The lamp intensity online monitor showed that the lamp efficiency decay was limited to within the first 12,000 h.

Nitrogen removal of high strength wastewater via nitritation/denitritation using a sequencing batch reactor

The sequencing batch reactor (SBR) process concept was applied to achieve efficient ammonium removal via nitrite under both laboratory and pilot-scale conditions. Both sets of experimental results show that without pH control or carbon addition the nitritation process consistently converted approximately 50% of the ammonium from biosolids dewatering liquids to nitrite with hydraulic retention times (HRT) as short as 10 h. The results from the pilot-scale study also indicate that the selective oxidation of ammonium to nitrite is a reliable process as the accumulation of nitrate was never an issue during a 330-day trial. The SBR process concept was extended to achieve complete nitrogen removal through nitritation and denitritation in the laboratory scale. The experimental results indicate that a total reduction of 96-98% of the ammonium nitrogen from biosolids dewatering liquids (influent concentration typically 1,200 g m(-3)) was achieved with a short HRT of 1.1 d and a removal rate of 1.05 kgNm(-3)d(-1). This process concept was tested at pilot scale where the nitritation process could be started up without temperature control in a short period of time. Nitrogen removal rates up to 1.2 kgNm(-3)d(-1) at an HRT of 0.88 d have been obtained. COD to nitrogen ratios required in the pilot plant were consistently in the range 1.6-1.9 kgCOD kg(-1)N removed.

Properties of Low‐substituted Cationic Starch Derivatives Prepared by Different Derivatisation Processes

AbstractCationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution 13C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid.The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different.The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.

The use of algal-bacterial biofilms to enhance nitrification rates in lagoons: experience under laboratory and pilot-scale conditions

Investigations were undertaken at the Western Treatment Plant (WTP), near Melbourne, Australia, to find ways of increasing overall ammonia and nitrogen removal rates in the WTP lagoon systems. Immobilisation of nitrifying bacteria in biofilms was one approach explored. Preliminary tests showed that algal/bacterial biofilms capable of achieving ammonia removal rates of 3 to 4 μg N/cm2·h would form on support surfaces immersed in the WTP lagoons. A laboratory-scale investigation was carried out to characterise the influence of parameters such as pH, temperature, COD level, dissolved oxygen concentration and incubation depth on biofilm performance. This study was followed by a pilot-scale investigation in a series of experimental ponds at the WTP. This compared the performance of three ponds, two containing 9360 m2 and 18240 m2 respectively of a geotextile biofilm support material and one containing no biofilm support material (the control pond). Ammonia removal rates comparable to those obtained in the preliminary tests were obtained when the biofilm support material was within the top 500 mm of the lagoon, i.e. in the photic zone. COD and suspended solids levels in the effluents from the biofilm containing ponds were substantially lower than those in the control pond effluent.

Cleaning of Acid Mine Drainage from An Uranium Mine By Means of a PassiveTreatment System

Acid mine drainage containing uranium, radium, iron and some non-ferrous metal ions were treated under pilot-scale conditions by means of a passive system consisting of an anoxic pond, an alkalinity producing anoxic drain, an aerobic wetland, and an anaerobic cell, arranged in series. In the anoxic pond containing a mixture of cattle manure and straw the content of the dissolved oxygen in the waters was reduced and most of the ferric ions were turned into the ferrous state to avoid deposition of metal precipitates within the subsequent alkalinity producing drain. In this drain the alkalinity of the waters was increased as a result of their contact with crushed limestone under anaerobic conditions. In the aerobic wetland iron was removed as iron hydroxide and radioactive elements were removed mainly by sorption by the emergent vegetation and microbial biomass grown in this wetland. Finally, in the anaerobic cell sulphate and metals were removed and additional alkalinity was produced as a result of the activity of sulphate reducing bacteria.