http://vital.seals.ac.za:8080/vital/access/manager/Index en-us 5 http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:9471 Wed 13 Mar 2024 10:44:10 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4195 Wed 12 May 2021 23:59:16 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4389 Wed 12 May 2021 23:17:08 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4394 Wed 12 May 2021 23:07:36 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10501 Wed 12 May 2021 23:06:15 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4071 Wed 12 May 2021 22:26:49 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4526 Wed 12 May 2021 22:26:11 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:2210 Wed 12 May 2021 22:20:43 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10310 Wed 12 May 2021 22:19:58 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:9473 Wed 12 May 2021 21:02:22 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:9622 Wed 12 May 2021 20:56:09 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10400 Wed 12 May 2021 20:17:48 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:3746 Wed 12 May 2021 19:48:45 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:9366 Wed 12 May 2021 19:43:24 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:3992 Wed 12 May 2021 19:32:33 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10102 Wed 12 May 2021 19:30:09 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:3443 Wed 12 May 2021 19:09:43 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:11108 Wed 12 May 2021 18:57:56 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5802 Wed 12 May 2021 18:57:17 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:11754 Wed 12 May 2021 18:42:59 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4076 10,000 mg/I), numerous metals and high concentrations of those metals (> 20 mg/l of platinum group metals) in the wastewater are the main challenges for biological removal of nitrogenous compounds from PMR wastewater. Nitrogenous compounds such as NH₄⁺-N and N0₃-N are strong metal ligands, which make it difficult to recover metals from the wastewater. Therefore, a bioprocess was developed for removal of nitrogenous compounds from carefully simulated PMR wastewater. A preliminary investigation of metal wastewater was carried out to determine its composition and physico-chemical properties, the ability to nitrify and denitrify under different pH conditions and denitrification with different carbon Source compounds and amounts. Even at pH 4, nitrification could be carried out. A suitable hydraulic retention time was found to be 72 hours. There was no significant difference between sodium acetate and sodium lactate as carbon sources for denitrification. Based on these results, a reactor comparison study was carried out using simulated PMR wastewater in three types of reactors: continuously stirred tank reactor (CSTR), packed-bed reactor (PBR) and airlift suspension reactor (ALSR). These reactors were fed with 30 mg/l of Rh bound in an NH₄⁺ based compound (Claus salt: pentaaminechlororhodium (III) dichloride). Total nitrogen removal efficiencies of > 68 % , > 79 % and > 45 % were obtained in the CSTR, PBR and ALSR, respectively. Serially connected CSTR-PBR and PBR-CSTR reactor configurations were then studied to determine the best configuration for maximum removal of nitrogenous compounds from the wastewater. The PBR-CSTR configuration gave consistent biomass retention and automatic pH control in the CSTR. Ammonium removal efficiencies > 95 % were achieved in both reactors. As poor nitrate removal was observed a toxicity study was carried out using respirometry and the half saturation inhibition coefficients for Pt, Pd, Rh and Ru were found to be 15.81, 25.00, 33.34 and 39.25 mg/l, respectively. A mathematical model was developed to describe the nitrogen removal in PMR wastewater using activated sludge model number 1 (ASMl), two step nitrification and metal toxicity. An operational protocol was developed based on the literature review, experimental work and simulation results. The optimum reactor configuration under the set conditions (20 mg/I of Rh and < 100 mg/I of NH₄⁺-N) was found to be PBR-CSTR-PBR process, which achieved overall NH₄⁺-N and N0₃⁻-N removal efficiencies of > 90 % and 95 %, respectively. Finally, a rudimentary microbial characterisation was carried out on subsamples from the CSTR and PBRsecondary. It was found that the CSTR biomass consisted of both rods and cocci while PBRsecondary consisted of rods only. Based on these experimental works, further research needs and recommendations were made for optimisation of the developed bioprocess for removal of nitrogenous compounds from PMR wastewater.]]> Wed 12 May 2021 18:01:58 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10396 Wed 12 May 2021 17:59:22 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:11301 Wed 12 May 2021 17:56:13 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:2780 Wed 12 May 2021 17:54:35 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10010 Wed 12 May 2021 17:50:31 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4588 Wed 12 May 2021 17:37:46 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:1196 Wed 12 May 2021 17:28:54 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:3932 Wed 12 May 2021 17:27:51 SAST ]]> 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http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:5678 Thu 13 May 2021 02:40:27 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:8238 Thu 13 May 2021 01:57:29 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:3930 Thu 13 May 2021 01:44:19 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:16129 Thu 13 May 2021 01:24:32 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10529 Thu 13 May 2021 01:07:53 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:9518 Thu 13 May 2021 00:58:04 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:4765 Thu 13 May 2021 00:31:56 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:10621 20 μm) accounted for > 65 percent of the Chl a, whereas during closed mouth conditions they accounted for about 55 percent of the Chl a biomass. Chlorophytes became the dominant taxon in the dry summer months but were replaced by cryptophytes and dinoflagellates during the wet season. When nutrient concentrations were low during low flow conditions in the Van Stadens Estuary mixotrophic microphytoplankton became an important fraction of the water column together with phototrophic dinoflagellates and cryptophytes. In the Maitland large sized chlorophytes were the dominant taxa in late spring and summer seasons and made up more than 80 percent of the cell numbers. In the Maitland before the floods in 2002 cyanophytes were the dominant group in late spring contributing more than 75 percent in cell abundance. Data from the short-term study in the Van Stadens Estuary showed similarities and differences in the Chl a response to increased river inflow. High river inflow initially reduced Chl a biomass followed by a recovery period of a couple of days compared to a 8 – 10 week recovery period in studies monitored over seasonal and annual temporal scales. The responses may be dissimilar but help to illustrate that there are similar response patterns to environmental forcing necessary to support phytoplankton biomass at different temporal scales. This study has demonstrated that flooding events caused by strong river flow cause breaching of the mouth, a reduction in salinity and marked nutrient input. Although the causes of flooding can be similar in both estuaries the resultant effects are varied and can alter the ability of the estuary to retain water. This study was able to demonstrate that the supply of macronutrients from the catchment was strongly correlated with rainfall (R2 = 0.67) and that phytoplankton growth mainly depended on an allochthonous source of macronutrients although internal supplies could be critical at times in controlling microalgal biomass.]]> Thu 13 May 2021 00:22:20 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:972 Thu 06 Jul 2023 16:10:51 SAST ]]> http://vital.seals.ac.za:8080/vital/access/manager/Repository/vital:2199 Mon 26 Aug 2024 15:32:04 SAST ]]>