Turbidity removal at twenty-one South African water treatment plants

Abstract: The Water Research Group at the Rand Afrikaans University undertook an ambitious sampling and monitoring programme at twenty-one South African water treatment plants during 2000 and 2001. At some of these plants, there were parallel but different treatment trains due to plant extensions being made at different times. A total of 25 full or partial treatment trains could therefore be monitored. A total of 115 plant visits were made over a period of fifteen months, with samples taken throughout the plant, covering the complete treatment train from raw to final water. Amongst other parameters, the turbidity of each sample was determined on site immediately upon sampling. This paper will summarise and interpret the resulting data set of approximately 1300 turbidity values. The paper will firstly characterise the raw and final waters respectively. In other words, how does typical raw water vary, and how good is the typical final water produced? The second part will summarise the typical performance of each of the treatment processes. In other words, what reduction in turbidity is typically achieved during settling, dissolved air flotation and filtration? The paper will make a practical contribution in providing a benchmark to all operators of treatment plants by: · being able to immediately "position" themselves within a typical range of raw water values. · judging their final water quality against what is generally achieved, and · evaluating and troubleshooting their individual process units against what is generally achieved

Diversities, affinities and diasporas: a southern lens and methodology for understanding multilingualisms

We frame multilingualisms through a growing interest in a linguistics and sociology of the ‘south’ and acknowledge earlier contributions of linguists in Africa, the Américas and Asia who have engaged with human mobility, linguistic contact and consequential ecologies that alter over time and space. Recently, conversations of multilingualism have drifted in two directions. Southern conversations have become intertwined with ‘decolonial theory’, and with ‘southern’ theory, thinking and epistemologies. In these, ‘southern’ is regarded as a metaphor for marginality, coloniality and entanglements of the geopolitical north and south. Northern debates that receive traction appear to focus on recent ‘re-awakenings’ in Europe and North America that mis-remember southern experiences of linguistic diversity. We provide a contextual backdrop for articles in this issue that illustrate intelligences of multilingualisms and the linguistic citizenship of southern people. In these, southern multilingualisms are revealed as phenomena, rather than as a phenomenon defined usually in English. The intention is to suggest a third direction of mutual advantage in rethinking the social imaginary in relation to communality, entanglements and interconnectivities of both South and North

Chapitre 14: Phytopathogènes et stratégies de contrôle en aquaponie

peer reviewedAmong the diversity of plant diseases occurring in aquaponics, soil-borne pathogens, such as Fusarium spp., Phytophthora spp. and Pythium spp., are the most problematic due to their preference for humid/aquatic environment conditions. Phytophthora spp. and Pythium spp. which belong to the Oomycetes pseudo-fungi require special attention because of their mobile form of dispersion, the so-called zoospores that can move freely and actively in liquid water. In coupled aquaponics, curative methods are still limited because of the possible toxicity of pesticides and chemical agents for fish and beneficial bacteria (e.g. nitrifying bacteria of the biofilter). Furthermore, the development of biocontrol agents for aquaponic use is still at its beginning. Consequently, ways to control the initial infection and the progression of a disease are mainly based on preventive actions and water physical treatments. However, suppressive action (suppression) could happen in aquaponic environment considering recent papers and the suppressive activity already highlighted in hydroponics. In addition, aquaponic water contains organic matter that could promote establishment and growth of heterotrophic bacteria in the system or even improve plant growth and viability directly. With regards to organic hydroponics (i.e. use of organic fertilisation and organic plant media), these bacteria could act as antagonist agents or as plant defence elicitors to protect plants from diseases. In the future, research on the disease suppressive ability of the aquaponic biotope must be increased, as well as isolation, characterisation and formulation of microbial plant pathogen antagonists. Finally, a good knowledge in the rapid identification of pathogens, combined with control methods and diseases monitoring, as recommended in integrated plant pest management, is the key to an efficient control of plant diseases in aquaponics.Cos

Relatedness of <I>Thremonyces Ianuginosus</I> strains producing a thermostable xylanase.

NatuurwetenskappeMikrobiologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]