published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

The production of 1,2-Dichloroethane (1,2-DCA) exceeds 5.44 billion kg per year, and is higher than that of any other industrial halogenated chemical. Improper disposal practices or accidental spills of this compound have made it a common contaminant of soil and groundwater. 1,2-DCA has been classified as a priority pollutant by the Environmental Protection Agency owing to its toxicity, persistence and bioaccumulation in the environment. It has also been shown to have mutagenic and potential carcinogenic effects on animals and humans. Bioremediation is emerging as a promising technology for the clean-up of sites contaminated with chlorinated hydrocarbons. However, sites co-contaminated with heavy metals and 1,2-DCA may pose a greater challenge for bioremediation, as the former pollutant could inhibit the activities of microbes involved in bioremediation. Therefore, this study was undertaken to quantitatively assess the effects of heavy metals on 1,2-DCA biodegradation and to investigate the use of biostimulation, bioaugmentation, dual bioaugmentation, and biosorption for remediation of water co-contaminated with 1,2-DCA and heavy metals in microcosms. The combined effect of 1,2-DCA and the respective heavy metals on the microbial population and diversity was also investigated. The minimum inhibitory concentrations (MICs) and concentrations of the heavy metals (arsenic, cadmium, mercury and lead) that caused half-life doubling (HLDs) of 1,2-DCA as well as the degradation rate coefficient (k1) and half-life (t1/2) of 1,2-DCA were measured in two different wastewater types. An increase in heavy metal concentration from 0.01–0.3 mM, resulted in a progressive increase in the t1/2 and relative t1/2 and a decrease in k1. The MICs and HLDs of the heavy metals were found to vary, depending on the heavy metals and wastewater type. In addition, the presence of heavy metals was shown to inhibit 1,2-DCA biodegradation in a dose-dependent manner, with the following order of decreasing inhibitory effect: Hg2+ > As3+ > Cd2+ > Pb2+. For the bioremediation experimental set-up, 150 ml wastewater was spiked with 1,2-DCA (2.5 mM) and the respective heavy metal in air-tight serum bottles (Wheaton). The bottles were biostimulated, bioaugmented, dual-bioaugmented or undergoing biosorption. The microcosms were incubated at 25 °C and the 1,2-DCA concentration was measured weekly. Co-contaminated water undergoing biostimulation, bioaugmentation and, in particular, dual bioaugmentation were observed to exhibit higher degradation of 1,2-DCA in the presence of the heavy metal, compared to co-contaminated water receiving none of the treatments. Dual bioaugmentation, proved to be most effective, resulting in up to 60% increase in 1,2-DCA degradation after 4 weeks, followed by bioaugmentation (55%) and biostimulation (51%). In addition, an increase in the total number of 1,2-DCA degrading bacterial population was observed in the bioaugmentated microcosms compared to those biostimulated, which corresponds to an increased 1,2-DCA degradation observed in the bioaugmentated co-contaminated microcosms. Dominant bacterial strains obtained from the co-contaminated microcosms were identified as members of the genera, Burkholderia, Pseudomonas, Bacillus, Enterobacter and Bradyrhizobiaceae, that have been previously reported to degrade 1,2-DCA and other chlorinated compounds. Some of these isolates also belong to genera that have been previously shown to be resistant to heavy metals. PCR-DGGE analysis revealed variations in microbial diversity over time in the different co-contaminated microcosms, whereby the number of bands was reduced, the intensity of certain bands increased, and new bands appeared. Agricultural biosorbents (AB) were found to adsorb heavy metals effectively when utilized at a concentration of 2.5%, with the level of biosorption found to be dependent on the type of AB as well on the type of heavy metal present. OP proved to be the most efficient biosorbent for the heavy metals tested, followed by CNF, and corn cobs (CC) least efficient; therefore CC was not used in further bioremediation experiments. Both orange peel (OP) and coconut fibre (CNF) were found to be excellent at removing heavy metals from co-contaminated microcosms, with OP removing 14.59, 74.79, 60.79 and 87.53% of As3+, Cd 2+, Hg2+ and Pb2+, respectively, while 10.03, 40.29, 68.47 and 70.00% of As3+, Cd2+, Hg2+ and Pb2+, respectively, was adsorbed by CNF. Consequently, a higher degradation of 1,2-DCA was observed in the presence of OP and CNF, compared to the untreated control. It can be concluded that the remediation approaches utilized in this study proved effective in the bioremediation of water co-contaminated with 1,2-DCA and heavy metals and may provide the foundation for new and innovative treatment strategies for co-contaminated sites. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

[Truncated abstract] An ethanol delivery system, consisting of silicone (poly(dimethylsiloxane)) tubing coiled and shaped as mats, was characterised and evaluated for its potential to act as a permeable reactive barrier (PRB), to promote reducing conditions and enable the enhanced bioremediation of a variety of groundwater contaminants in situ. Aqueous ethanol solutions were recirculated through the inner volume of the silicone polymer tubing in the mat, to allow permeation and delivery of ethanol by diffusion through the tubing walls to a target contamination zone. The aim of the system was to provide control over subsurface geochemistry by overcoming carbon source limitations, and as a result stimulate indigenous bacteria to remove contaminants. The physical properties of the silicone tubing were initially characterised, which included the determination of the ethanol sorption and diffusion properties of the tubing. A model for the mass of ethanol transferred via diffusion from an aqueous solution on the inner volume of a length of polymer tubing was developed to enable prediction of the ethanol delivery capacity of the silicone polymer mats. A number of large-scale laboratory column studies were then conducted to validate this ethanol mass delivery model, and to evaluate the use of silicone polymer mats to deliver ethanol and promote the biodegradation of a range of different contaminated groundwaters. The laboratory column experiments were observed to produce ethanol mass flux delivery statistically similar to that predicted by the model; however this was only with the application of an effective diffusion coefficient within the model, which was determined from the model under subsurface-simulated conditions. Ethanol delivery using the silicone tubing polymer mat system was also quantified in a pilot field-scale demonstration. The mass of ethanol delivery in the field was shown to be within the range of model-predicted ethanol delivery; however delivery was not as consistent and predictable as that observed in the column studies. Successful ethanol enhanced nitrate contamination removal (via denitrification) was observed at a field scale. For field applications, this innovative polymer mat amendment delivery system may provide targeted, predictable and cost-effective amendment delivery compared to aqueous injection methods for groundwater bioremediation, however, knowledge and quantification of the hydrogeology of the particular field site is required. Two other ethanol-driven biologically-mediated contaminant removal processes were also investigated in the laboratory-scale soil column studies, and included the assessment of the removal of dissolved metals/sulfate via sulfate reduction and metalsulfide precipitation, and the removal of trichloroethene via reductive dechlorination.

Made available in DSpace on 2016-01-13T13:27:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-24. Added 1 bitstream(s) on 2016-01-13T13:33:00Z : No. of bitstreams: 1 000854786.pdf: 1509859 bytes, checksum: d70b0ac9c6f747deccb46e85615c339e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A aquicultura tornou-se uma importante e lucrativa atividade agrícola, com grande interesse comercial e social, entretanto pode ser altamente impactante para o ambiente se não manejada de forma correta. O manejo adequado dos sistemas de criação de peixes em tanques e viveiros consiste na manutenção da qualidade da água, já que a produção de organismos aquáticos é dependente de subsídios externos como o aporte de nutrientes, gerando resíduos, cujo acúmulo no sistema, pode ser prejudicial ao peixe, à microbiota aquática e ao corpo receptor e efluente dessa atividade. Macrófitas aquáticas e o perifíton são importantes ferramentas agindo como biofiltros e minimizando as concentrações de material orgânico, influenciando na qualidade da água e nos organismos existentes. O objetivo desse trabalho foi avaliar a eficiência do tratamento da água de tanques de piscicultura e seus efluentes, utilizando macrófitas aquática e/ou perifíton, avaliando a influência destes na qualidade da água e consequente influência na comunidade planctônica. O trabalho foi realizado no Centro de Aquicultura da Unesp (Caunesp), onde foram utilizados 4 tanques de 40 m2 e 1,5 de profundidade, com tratamentos diferentes (macrófita e/ou perifíton) recebendo a mesma água de abastecimento. Foi observado que a presença dos tratamentos apresentou influência direta nas condições bióticas e abióticas dos tanques, atuando na riqueza e abundância das espécies planctônicas. Através dos resultados obtidos foi observado que a água do tanque sem planta aquática e/ou perifíton apresentou associação com temperatura, condutividade, ortofosfato, fósforo total, DBO5, coliforme termotolerante, nitrogênio amoniacal total, sólidos totais suspensos e turbidez, assim como o efluente, que também esteve relacionado a essas variáveis. O sedimento dos tanques acumulou concentrações diferentes de nutrientes e metais, e o tanque controle... / Aquaculture has become an important and lucrative agricultural activity, with great commercial and social interest, however can be highly impacting to the environment if not managed properly. Proper management of fish farming in pond systems and nurseries is to maintain water quality, since the production of aquatic organisms is dependent on external subsidies as the supply of nutrients, generating waste, whose accumulation in the system, can be harmful the fish, the aquatic microbiota and the receiving body and effluents that activity. Macrophytes and periphyton are important tools acting as biofilters and minimizing the concentrations of organic material, influencing the quality of water and the organisms living there. The aim of this study was to evaluate the efficiency of water treatment fishponds and their effluent using aquatic macrophytes and / or periphyton evaluating their influence on water quality and the consequent influence on plankton community. The study was developed in UNESP Aquaculture Center (CAUNESP), where they were used four tanks of 40 m2 and 1.5 deep, with different treatments (macrophyte and / or periphyton) receiving the same water supply. It was observed that the presence of the treatments had a direct influence on biotic and abiotic conditions of the ponds, acting in richness and abundance of planktonic species. Through the results it was observed that the pond without aquatic plant and / or periphyton was associated with variables, temperature, conductivity, orthophosphate, total phosphorus, BOD5, thermotolerant coliform, total ammonia nitrogen, total suspended solids and turbidity. This condition provided the predominance of plankton community correlated positively to these factors, such as Rotifers, Copepods Cyclopoida, Cyanobacteria and Xanthophyceae, considered indicators of eutrophic bodies environment. In the treatment only with macrophytes, lower nutrient concentrations and increased transparency ... / FAPESP: 2013/03070-0

Orientador: Lúcia Helena Sipaúba Tavares / Banca: Maria Stela Maioli Castilho Noll / Banca: Maria da Graça Gama Melão / Resumo: As plantas aquáticas são componente importante de um "wetland" construído utilizado para tratamento de efluentes de aquicultura, devido a sua habilidade de absorver nutrientes da água. Estas macrófitas possibilitam melhores condições para microrganismos aquáticos que auxiliam na melhora da qualidade de água. O presente estudo objetivou avaliar o crescimento, a composição química e a fauna associada à Eichhornia crassipes, e as condições físicas e químicas da água e sedimento em um "wetland" (21°11'S; 48°18'O) de uma fazenda de aquicultura, em duas etapas de crescimento da macrófita (Fevereiro à Maio e Julho à Outubro de 2014). A fauna associada a E. crassipes foi amostrada com quadrantes flutuantes (0,09m²); as macrófitas foram lavadas e o plâncton e macrofauna foram fixadas com formalina a 4%; as espécimes foram identificadas e contadas. Diptera, Odonata, Rotifera, Copepoda, Protozoa, Ostracoda and Nematoda estiveram presentes em todas as coletas nas duas etapas de crescimento da E. crassipes. Vorticella sp. foi o gênero dominante nas duas etapas, sendo que Protozoa e Rotifera apresentaram maior abundância. A 1ª etapa de crescimento apresentou maiores valores de nitrogênio e fósforo na água e a 2ª etapa a maior retenção de nutrientes no sedimento antes do banco de aguapé. De acordo com os resultados obtidos foi possível comprovar que o tempo máximo que a E. crassipes deve ser mantida no "wetland" para retenção dos resíduos provenientes da aquicultura é de 60 dias, sendo nece... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aquatic plants are a relevant component of a constructed wetland for the treatment of aquaculture effluents due to their capacity in absorbing nutrients from water. The macrophytes provide better conditions for aquatic microorganisms to improve water quality. Current research evaluated the growth, chemicals composition and fauna associated with Eichhornia crassipes, the physical and chemical conditions of water, and sediment within the system for effluent treatment on an aquaculture farm (21°11'S; 48°18'W) at two growth periods of aquatic plant growth (February to May and July to October 2014). Fauna associated to E. crassipes were sampled with floating quadrants (0.09 m²); the macrophytes were washed and the plankton and macrofauna were fixed with 4% formalin; the specimens were then identified and counted. Diptera, Odonata, Rotifera, Copepoda, Protozoa, Ostracoda and Nematoda occurred at all collections in both periods of E. crassipes growth. Vorticella sp. was the predominant genus in the two periods; Protozoa and Rotifera species were the most abundant. The first period of growth revealed higher nitrogen and phosphorus rates in the water, whilst in the second period there was a greater nutrient retention in the sediment in front of the stand of macrophyte. Results showed that 60 days is the maximum time that E. crassipes may be maintained in the wetland to retain wastes from aquaculture; after this period biomass and the accumulation of nutrients in the vegetal tissue... (Complete abstract click electronic access below) / Mestre

Orientador: Lúcia Helena Sipaúba Tavares / Banca: Rodrigo Ney Millan / Banca: Maria do Carmo Calijuri / Resumo: A aquicultura tornou-se uma importante e lucrativa atividade agrícola, com grande interesse comercial e social, entretanto pode ser altamente impactante para o ambiente se não manejada de forma correta. O manejo adequado dos sistemas de criação de peixes em tanques e viveiros consiste na manutenção da qualidade da água, já que a produção de organismos aquáticos é dependente de subsídios externos como o aporte de nutrientes, gerando resíduos, cujo acúmulo no sistema, pode ser prejudicial ao peixe, à microbiota aquática e ao corpo receptor e efluente dessa atividade. Macrófitas aquáticas e o perifíton são importantes ferramentas agindo como biofiltros e minimizando as concentrações de material orgânico, influenciando na qualidade da água e nos organismos existentes. O objetivo desse trabalho foi avaliar a eficiência do tratamento da água de tanques de piscicultura e seus efluentes, utilizando macrófitas aquática e/ou perifíton, avaliando a influência destes na qualidade da água e consequente influência na comunidade planctônica. O trabalho foi realizado no Centro de Aquicultura da Unesp (Caunesp), onde foram utilizados 4 tanques de 40 m2 e 1,5 de profundidade, com tratamentos diferentes (macrófita e/ou perifíton) recebendo a mesma água de abastecimento. Foi observado que a presença dos tratamentos apresentou influência direta nas condições bióticas e abióticas dos tanques, atuando na riqueza e abundância das espécies planctônicas. Através dos resultados obtidos foi observado que a água do tanque sem planta aquática e/ou perifíton apresentou associação com temperatura, condutividade, ortofosfato, fósforo total, DBO5, coliforme termotolerante, nitrogênio amoniacal total, sólidos totais suspensos e turbidez, assim como o efluente, que também esteve relacionado a essas variáveis. O sedimento dos tanques acumulou concentrações diferentes de nutrientes e metais, e o tanque controle... / Abstract: Aquaculture has become an important and lucrative agricultural activity, with great commercial and social interest, however can be highly impacting to the environment if not managed properly. Proper management of fish farming in pond systems and nurseries is to maintain water quality, since the production of aquatic organisms is dependent on external subsidies as the supply of nutrients, generating waste, whose accumulation in the system, can be harmful the fish, the aquatic microbiota and the receiving body and effluents that activity. Macrophytes and periphyton are important tools acting as biofilters and minimizing the concentrations of organic material, influencing the quality of water and the organisms living there. The aim of this study was to evaluate the efficiency of water treatment fishponds and their effluent using aquatic macrophytes and / or periphyton evaluating their influence on water quality and the consequent influence on plankton community. The study was developed in UNESP Aquaculture Center (CAUNESP), where they were used four tanks of 40 m2 and 1.5 deep, with different treatments (macrophyte and / or periphyton) receiving the same water supply. It was observed that the presence of the treatments had a direct influence on biotic and abiotic conditions of the ponds, acting in richness and abundance of planktonic species. Through the results it was observed that the pond without aquatic plant and / or periphyton was associated with variables, temperature, conductivity, orthophosphate, total phosphorus, BOD5, thermotolerant coliform, total ammonia nitrogen, total suspended solids and turbidity. This condition provided the predominance of plankton community correlated positively to these factors, such as Rotifers, Copepods Cyclopoida, Cyanobacteria and Xanthophyceae, considered indicators of eutrophic bodies environment. In the treatment only with macrophytes, lower nutrient concentrations and increased transparency ... / Mestre

Orientador: Bruno Coraucci Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-17T01:24:25Z (GMT). No. of bitstreams: 1 Senna_PaulaReginaCoeliBarbosa_M.pdf: 5617120 bytes, checksum: 340fdd25e903f12f594069b1c57b10b9 (MD5) Previous issue date: 2010 / Resumo: O excesso de nutrientes, provenientes principalmente de esgotos sanitários, que são lançados em corpos receptores pode levar ao processo de eutrofização, ocasionando efeitos adversos ao meio ambiente. Surge então a necessidade do tratamento avançado ser considerado no planejamento dos recursos hídricos. Deste modo, avaliou-se a desnitrificação de uma parcela do efluente sanitário proveniente UNICAMP. Para isso, esta água residuária foi tratada por um filtro anaeróbio com recheio de bambu (Bambusa tuldoides), operado com tempo de detenção hidráulica de 9 horas, sendo logo após direcionada para um filtro de areia (aeróbio). Tendo como alternativa o reuso agrícola, o processo de desnitrificação do efluente é fundamental evitando-se a percolação do nitrato no solo. Na primeira fase do estudo, o efluente dos filtros de areia foi aplicado em reator anaeróbio com recheio de brita, variando-se as vazões de fonte de carbono de 20 para 25L e o tempo de detenção hidráulica de 4 para 7 horas. Na segunda fase, o efluente nitrificado no filtro de areia foi recirculado para o filtro anaeróbio com recheio de bambu, em proporções de 15% e 20% em relação ao esgoto bruto. As duas fases do tratamento atingiram até 60% de desnitrificação, com efluente dentro de padrões de lançamento para DQO, DBO para fase 1 como também eficiência na desinfecção referente a Coliformes Totais e Escherichia Coli de acordo com Legislação, podendo o efluente ser lançado em corpos hídricos de classe 2, como também aplicado em práticas de reúso de classe A, B e C / Abstract: The excess nutrients, mainly from sewage released into receptors, can lead to eutrophication, causing adverse effects to the environment and also the health of the population. Then comes the need for advanced treatment be considered in the planning of water resources. Thus, we estimated the denitrification of the University of Campinas Hospital's sanitary effluent, through a combination of aerobic and anaerobic filter. To do so, the wastewater was treated by an anaerobic filter filled with bamboo (Bambusa tuldoides), operated with hydraulic retention time of 9 hours, forwarded by a sand filter. Intermittent operation was used to ensure a wide ground layer oxygenation, causing nitrification of 80% of the affluent. Denitrification is an essential process when reusing wastewater for agricultural purposes, as it prevents the percolation of nitrate in the soil. The denitrification analysis was done in two phases. First, the sand filter's effluent hás been applied into the anaerobic reactor filled with gravel with flows of carbon source of 20 and 25L and hydraulic retention time from 4 to 7 hours. The obtained values were within the standards for reuse. Second, the nitrified effluent in sand filter is recirculated to the anaerobic filter filled with bamboo, in proportions of 15% and 20% compared to raw sewage. Both phases of the treatment achieved a rate of 60% effluent denitrification and, for first phase, the effluents are in agreement with the standards releases of COD, BOD as well as the disinfection efficiency regarding coliform and Escherichia Coli. According to law, the effluent may be flowed out into bodies of water Class 2 and also can be applied in reuse practices of class A, B and C / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

Faecal contamination in water is detected using appropriate microbial models such as total coliforms, faecal coliforms and E. coli. Βeta-D-Galactosidase (β-GAL) and Beta-D-glucuronidase (β-GUD) are two marker enzymes that are used to test for the presence of total coliforms and E. coli in water samples, respectively. Various assay methods have been developed using chromogenic and fluorogenic substrates. In this study, the chromogenic substrates chlorophenol red β-D-galactopyranoside (CPRG) for β-GAL and p-nitrophenyl-β-D-galactopyranoside (PNPG) for β-GUD were used. Potential problems associated with this approach include interference from other organisms present in the environment (e.g. plants, algae and other bacteria), as well as the presence of certain chemicals, such as phenolic compounds in water. Phenolic compounds are present in the aquatic environment due to their extensive industrial applications. The USA Enviromental Protection Agency (EPA) lists 11 Priority Pollutant Phenols (PPP) due to their high level of toxicity. This study investigated the interfering effects of the eleven PPP found in water on the enzyme activities of both the β-GAL and β-GUD enzyme assays. The presence of these PPP in the β-GAL and β-GUD enzyme assays showed that over and underestimation of activity may occur due to inhibition or activation of these enzymes. Three types of inhibition to enzyme activities were identified from double reciprocal Lineweaver-Burk plots. The inhibition constants (Ki) were determined for all inhibitory phenolic compounds from appropriate secondary plots. Furthermore, this study presented a validated reverse phase high performance liquid chromatography (RP-HPLC) method, developed for the simultaneous detection, separation and determination of all eleven phenolic compounds found in the environment. This method demonstrated good linearity, reproducibility, accuracy and sensitivity. Environmental water samples were collected from rivers, streams, industrial sites and wastewater treatment plant effluent. These samples were extracted and concentrated using a solid phase extraction (SPE) procedure prior to analysis employing the newly developed HPLC method in this study. Seasonal variations on the presence of the PPP in the environment were observed at certain collection sites. The concentrations found were between 0.033 μg/ml for 2,4-dinitrophenol in a running stream to 0.890 mg/ml for pentachlorophenol from an tannery industrial site. These concentrations of phenolic compounds found in these environments were able to interfere with the β-GAL and β-GUD enzyme assays.

Ph.D. (Biochemistry) / Please refer to full text to view abstract

Mine wastewaters generated during active production operations, and decanting streams following mine closure have major environmental impacts, and volumes requiring treatment are expected to increase substantially as the South African mining industry matures. Biological treatment of mine waters has been the subject of increasing interest, where sulphate reducing bacteria are employed for the reduction of sulphate to sulphide, precipitation of metals and the production of alkalinity. However, the sulphide if not removed from the system can be oxidised back to sulphate. As a result there have been limitations especially in the provision of technological options that are sustainable over the long-term, where the total sulphur (in its different forms) can be removed from the system. These, however, are the subject of a number of constraints including, importantly, the process capability to remove reduced sulphur from the treated stream, in one of its oxidation states, and thus linearise the biological sulphur cycle. This remains a major bottleneck in the development of biological wastewater treatment technology. Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and it has been suggested that they play a role in the biological cycling of sulphur. The use of sulphur biofilms for the removal of elemental sulphur was identified in this study as a possible means for addressing the technological bottleneck, especially in passive wastewater treatment systems. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, the microbial species responsible for their occurrence or bio-process applications of the system. A linear flow channel reactor was developed to simulate natural conditions and enabled the study of floating sulphur biofilm under controlled laboratory conditions. It was observed that these biofilms developed through three distinct stages termed Thin, Sticky and Brittle films. A microprobe study showed the presence of a steep Redox gradient established across (260 to 380 μm) depth of the floating sulphur biofilm of ~ 0 to -200 mV (top to bottom), which correlated with pH and sulphide gradients across the system. Structural investigations embedded in an exopolymeric matrix containing clearly defined channels and pores. Sulphur crystals were found to develop within the biofilm and above a certain size these disengaged and then settled in the liquid phase below the biofilm. These features, together with the ability of the biofilm to remain suspended at the air/water interface thus provide the surface requirement, and indicate that these structures may be understood as “true” biofilms. In order to study an apparent functional differentiation within the floating sulphur biofilm system, a method was developed to expand its various components over a 13 cm length of agarose tube and across which an oxygen/sulphide gradient was established. This was done by inserting a sulphide plug in the bottom of the tube, overlaying this with the biofilm mixed and suspended in agarose and leaving the tube to open air. After allowing for growth, the different components of the microbial population occurring at various levels across the oxygen/sulphide gradient were sampled. The microbial population was found to resort in distinct functional layers. Aerobes including Acidithiobacillus and Azoarcus, Acidithiobacillus, Thiothrix, Thiovirga and Sulfurimonas were found in the upper oxidised layer. Aerobe and facultative anaerobes such as Chryseobacterium, Bacteroides and Planococcus were found in the middle and heterotrophic anaerobes such as Brevundimonas and uncultured anaerobes were found in the bottom anoxic layer. This enabled the development of a first descriptive structural/functional model accounting for the performance of floating sulphur biofilms. The potential of the floating sulphur biofilm for use as a bioprocess unit operation for sulphide removal in lignocellulose-based low-flow passive systems for acid mine drainage wastewater treatment was investigated. The linear flow channel reactor was scaled up and it was shown that the optimum sulphide removal of 74 % and sulphur recovery of 60 % could be achieved at 20 °C. In a further scale up of the linear channel reactor, the floating sulphur biofilm reactor was developed and operated. Sulphide removal and sulphur recovery of 65 and 56 % respectively was measured in the process. An understanding of the nature and function of floating sulphur biofilms and the further development of their potential application in sulphide removal in aquatic systems may provide a useful contribution to the treatment of acid mine drainage and other sulphidic wastewaters.