Environmental Technology

Bonthrone, K. M.; Quarmby, J.; Hewitt, C. J.; Allan, V. J. M.; Paterson-Beedle, M.; Kennedy, J. F.; Macaskie, L. E.

doi: 10.1080/09593330.2000.9618893pmid: N/A

Cells of a heavy metal-accumulating Citrobacter sp. appeared electron-opaque under the electron microscope when pre-grown in medium containing lactose and inorganic phosphate as the respective carbon and phosphorus sources, compared to cells supplied with glycerol and glycerol 2-phosphate. This was attributable to a greater proportion of bound metal cations, as analysed using proton induced X-ray emission analysis of extracted extracellular polymeric material (EPM). This was associated with a greater content of EPM-associated phosphorus and also an enhanced activity of isolated EPM to accumulate uranyl ion, to 23% of the polymer dry weight. EPM from glycerol 2-phosphate-grown cells, analysed using 31P nuclear magnetic resonance spectroscopy, gave several major phosphorus resonances between −1 and 2 ppm, in accordance with published spectra for enterobacterial lipopolysaccharide. Addition of Cd2+ promoted a shift downfield of the P resonances to a new, common, resonance at 3 ppm which was similar to that observed in native, Cd-unchallenged EPM obtained from inorganic phosphate-pregrown cells. The two types of polymer were morphologically distinct, with a shift to a more defined structure on addition of Cd2+ to the EPM from glycerol phosphate-grown cells. The two types of 31P spectra of the EPM were influenced by the pregrowth phosphorus source, and not by the carbon source. In contrast, analysis of the monosaccharide content of the EPM by gas chromatography and high performance liquid chromatography showed that the main components, rhamnose, glucose and ribose, were unaffected by the pre-growth phosphate source but cells pre-grown in glycerol medium had a higher proportion of glucose residues (ratios of glucose:rhamnose of 4:1 and 2.5:1 in glycerol and lactose-pregrown cells, respectively), and a higher content of EPM monosaccharides, overall, in the lactose-grown cultures. Restriction of carbon or nitrogen source by growth in continuous culture and analysis of the EPM gave major 31P resonances in the region of −1 to 3 ppm, while growth under phosphate-limiting continuous culture showed only one major species, at 1 ppm. The data illustrate that the composition of the cell surface polymers, and the ability of these to sorb heavy metal, are functions of the environment in which the cells are grown. This has implications in the application of biosorption techniques to the removal of heavy metals from wastes.

Annachhatre, A. P.; Amornkaew, A.

doi: 10.1080/09593330.2000.9618894pmid: N/A

Degradation of cyanide and its toxic effects on anaerobic biogranules were investigated in batch serum bottles using synthetic wastewater. Batch anaerobic cultures were exposed to a range of initial cyanide concentrations from 1 to 100 mg l−1 for a period of 48 hours. Cyanide degradation rate increased with initial cyanide concentration in the batch. Maximum cyanide degradation rate upto 35–40 mg l−1d−1 was recorded. Activity of biogranules was affected due to the presence of cyanide. Methane production rate decreased with increase in initial cyanide concentration in the batch. A methane production rate of 0.11 ml ml−1d−1 was recorded for 10 mgCN l−1 compared to 0.42 ml ml−1d−1 for control containing no cyanide. Results from Microtox toxicity tests confirmed degradation of cyanide occurring in batch tests. EC50 for exposure time of 5 minutes and 15 minutes increased with respect to batch time indicating reduction in cyanide contents and its toxicity. A generalized procedure to estimate batch time for reducing cyanide toxicity to a specific level is also included.

Rhee, E.; Speece, R. E.

doi: 10.1080/09593330.2000.9618895pmid: N/A

Computer controlled reactors were used to probe the maximal rate of anaerobic biodegradation of methylene chloride, carbon tetrachloride, and 1,1,1-trichloroethane using three important methane precursors (formic, acetic and propionic acids) as primary substrates. Maximal biodegradation rate was defined as that loading rate of the chlorinated aliphatic compounds which was achieved at a primary substrate removal rate of 50 % of the rate achieved with no chlorinated aliphatic present. The systems were controlled by a computer in response to the pH of the reactor in order to maintain an unlimiting concentration of the primary substrate in the reactors. For methylene chloride, carbon tetrachloride, and 1,1,1-trichloroethane 62 - 88, 96 - 99 and 93 - 97% respectively was biodegraded at maximal loading rates of 5.2 - 61, 19 - 79 and 31 - 110 mg l−1 of reactor day−1 for formate, acetate and propionate primary substrates respectively. Specific chlorinated organic removal rates, the most sensitive class of microorganisms, and the fate of these three compounds also were examined. With acetate as the primary substrate, the amount of methylene chloride, carbon tetrachloride and 1,1,1-trichloroethane removed per acetate converted to methane was 0.0023, 0.0027 and 0.045 mg mg−1 respectively. Based upon the bacterial mass, the conversion rate was 0.0085, 0.012 and 0.017 mg of methylene chloride, carbon tetrachloride and 1,1,1-trichloroethane mg−1 VSS day−1 respectively.

Basri, H. B.

doi: 10.1080/09593330.2000.9618896pmid: N/A

A prototype expert system, called the Leachate Management Advisor (LMA), has been developed to assist in the conceptual design of leachate management facilities in a sanitary landfill. The expert system aims to establish the expected leachate production and its polluting potential, recommend a policy for leachate containment, investigate whether lining, leachate collection or treatment is/are necessary, and, if so, perform conceptual design for the required components. An expert system shell, Kappa-PC, was selected as the development tool for the LMA prototype because of its object-oriented approach, which combines the two main knowledge representation techniques for expert systems, i.e. production rules and objects. An object-oriented model of the domain was successfully developed where the rule-based reasonings and other decision processes operate on or across objects representing real-world entities of the domain. Expertise in the knowledge base was acquired from 12 textual sources and 10 landfill practitioners in Malaysia. The overall performance of the LMA was evaluated to be satisfactory based on a case study of an actual landfill site.

Önkal-Engin, G.; Wibulswas, R.; White, D. A.

doi: 10.1080/09593330.2000.9618897pmid: N/A

Humic acid occurs in waters naturally. Humic acid gives its characteristic yellowish to brownish colour to water making it unaesthetic. In this study, synthetic hydrotalcite, hydrotalcite-like compounds, calcined hydrotalcites and modified forms of Montmorillonite were used to remove humic acid from water. The results indicated that surfactant treated Montmorillonite was more effective than other forms of modified Montmorillonite. In the case of hydrotalcites, hydrotalcite-like compounds removed more humic acid than synthetic hydrotalcite. Surfactant treated Montmorillonite, however, was found to be a better adsorbent when compared to other clay samples.

Turan, M.

doi: 10.1080/09593330.2000.9618898pmid: N/A

Biofilm growth and detachment mechanisms in anaerobic fluidized bed reactors (AFBRs) were studied. The hydrodynamic characteristics and the energy dissipation of the biological fluidized bed were investigated. Biofilm growth experiments in a pilot-scale AFBR were performed and attached biomass concentration was observed to increase rapidly in the upper part of the bed. The measured and predicted biomass concentrations showed good agreement. Biomass loss due to hydrodynamic forces and particle collisions were also investigated during the experimental studies. Some relationships applicable to the AFBRs were obtained for the biofilm specific detachment rate (rb) versus the fraction solids (Cv), the hydrodynamic shear stress (τ) and the Reynolds number of the flow (Re) with good accuracy. Detachment rate increased with the increment in Cv and τ and decreased with increase of Re. It was found that the shear stress and particle collisions play a major role in the detachment mechanism.

Agamuthu, P.; Choong, Looi Chee; Hasan, Shameem; Praven, V. V.

doi: 10.1080/09593330.2000.9618899pmid: N/A

Composting as a biological waste treatment process holds a lot of promise in Malaysia. Although composting has a long history of application, it is difficult to find published work in the area of kinetics, which is regarded as important from the engineering point of view. As composting operates on the same general biochemical principles as all biological systems, enzyme kinetics concepts could be applicable in the formulation of kinetic model of the composting process In this study, composting experiments were performed on oil palm empty fruit bunches, garden wastes, chicken dung and garden waste together with municipal sewage sludge. A commercial compost starter was evaluated for its efficacy to speed up the composting process. The kinetic rate constants Km, K′m, Rm and R′m were determined experimentally. It was observed that the Michealis constant (Km) values were fairly constant (between 1.20 to 1.84) for each waste irrespective of whether compost starter was added. As for the maximum or limiting velocity, Rm and R′m values, it was observed that the values were higher with the addition of compost starter, the increase depending on the type of agro-waste and in the case of garden waste and EFB it was almost double when compared to control. The growth characteristics of actinomycetes, bacteria and fungi involved in composting were also evaluated and based on μm and Ks the addition of compost starters showed a positive effect on the growth rate of these microorganisms.

Jiménez, L.; Pérez, I.; García, J. C.; Trigo, M. D.; Navarro, E.

doi: 10.1080/09593330.2000.9618900pmid: N/A

Black liquor obtained in the bleaching with the cartazyme anzime - oxyen - hydrogen peroxide (XOP) sequence of soda pulp from wheat straw was characterized. A central composite design was used to examine the influence of operating variables of the O bleaching step (temperature, time and soda concentration) on various properties of the black liquor (pH, chemical oxygen demand, total carbon, total organic carbon, total inorganic carbon, total solids, total volatile solids, total mineral solids and colour). Equations that relate the dependent variables to the independent ones were derived that predict the former with errors less than 25%. The least polluting black liquor was obtained by using a medium temperature (100 °C), a medium soda concentration (1.65%) and a short time (15 min) in the O step of the XOP bleaching sequence. Under these conditions, the properties of pulp bleached with the XOP sequence (yield, brightness and viscosity), and those of the paper sheets obtained from them (breaking length, stretch, burst index, tear index and double fold number), were found to be only 6% smaller than the optimum values in most instances.

Choung, J. W.; Xu, Z.; Finch, J. A.

doi: 10.1080/09593330.2000.9618901pmid: N/A

Treating acid mine drainage (AMD) using ambient temperature ferrite (ATF) process is attractive but challenging due to the complex nature of AMD solution chemistry. Calcium, associated with sulfate and ferric oxy-hydroxides, has been shown to interfere with ferrite formation. A novel process has been developed based on the use of carbonates to scavenge the soluble calcium followed by neutralization with carefully controlled solution chemistry. With this process, magnetic precipitates of spinel structure are formed from a simulated AMD within a practically feasible reaction period, while producing an environmentally safe effluent.

Pérez-Martínez, J. I.; Ginés, J. M.; Morillo, E.; Rodríguez, Mª L. G.; Moyano, J. R.

doi: 10.1080/09593330.2000.9618902pmid: N/A

In the present paper the complexation of 2,4-Dichlorophenoxyacetic acid (2,4-D) and a partially methylated-β-Cyclodextrin (PM-β-CD) has been studied in solution, being determined from the phase solubility diagram an apparent stability constant of 359.0 M−1 for the complex. Solid complexes were also obtained by different processing methods being investigated the inclusion process by scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, hot stage microscopy and x-ray diffractometry. Dissolution rate studies of the non-complexed and complexed pesticide were carried out. In all the cases the complex formation improved the dissolution rate. 2,4-D / PM-β-CD complexes may find use in pesticide formulations since they present important advantages.