Scum materials

The detection and analysis, including quantification, of cyanobacterial toxins are essential for monitoring their occurrence in natural and controlled waters used for agricultural purposes, potable supplies, recreation and aquaculture. Risk assessment of the cyanobacterial toxins for the protection of human and animal health, and fundamental research, are also dependent on efficient methods of detection and analysis. In this article we discuss the methods developed and used to detect and analyse cyanobacterial toxins in bloom and scum material, water and animal/clinical specimens, and the progress being made in the risk assessment of the toxins. 

From dense scum material toxins can be released when cells start to lyse. It can happen that scums are washed ashore where they dry forming crusts along the shoreline. A release of toxins can then occur with a time delay when the cells get submerged or rehydrated again. ... 

Anionic surfactants are the most commonly used class of surfactant. Anionic surfactants include sulfates such as sodium alkylsulfate and the homologous ethoxylated versions and sulfonates, eg, sodium alkylglycerol ether sulfonate and sodium cocoyl isethionate. Nonionic surfactants are commonly used at low levels ( 1 2%) to reduce soap scum formation of the product, especially in hard water. These nonionic surfactants are usually ethoxylated fatty materials, such as H0CH2CH20(CH2CH20) R. These are commonly based on triglycerides or fatty alcohols. Amphoteric surfactants, such as cocamidopropyl betaine and cocoamphoacetate, are more recent surfactants in the bar soap area and are typically used at low levels (<2%) as secondary surfactants. These materials can have a dramatic impact on both the lathering and mildness of products (26). 

In the Slimmer of 1989, Rutland Water, the largest man-made lake in Western Europe and which supplies potable water to approximately 500 000 people in the East of England, contained a heavy bloom of Microcystis aeruginosa. By the end of the summer, a number of sheep and dogs had died after drinking from the bloom and concentrated scum. Analysis revealed that the cyanobacterial bloom material was toxic to laboratory mice, and that rumen contents from a poisoned sheep contained fivemicrocystin variants.Microcystins were detected in waters used for recreation in Australia at concentrations greater than 1 mg per... 

Chemical Reactivity - Reactivity with Water Reacts slowly, forming heavy scum and liberating carbon dioxide gas. Dangerous pressure can build up if container is sealed Reactivity with Common Materials No hazardous reaction unless confined and wet Stability During Transport Stable if kept sealed and dry Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor qf Polymerization Not pertinent. 

Soap works because the nonpolar end dissolves in dirt (oil), leaving the polar end outside the dirt. This combination is known as a micelle (see Figure 16-30). To the surrounding water molecules, the micelle appears as a very large ion. These ions tire water-soluble and repel each other due to their like charges, a behavior that causes them to remain separated. Metal ions in hcird water (Ca VMg VFe ) cause a precipitate to form because they react with carboxylate ions to form an insoluble material (also known as the soap scum hanging around the bathtub or shower). 

In hard water areas all over the world, it is difficult to make the soap lather. Instead, the water becomes cloudy. This cloudiness is caused by the presence of a solid material (a precipitate) formed by the reaction of the dissolved substances in the water with soap (basically sodium stearate) and it is a real problem. This white precipitate is known as scum (Figure 11.35). 

Figure 15 6B Arsenic distribution in the scum, slag and landfill materials (from 25 m X 25 m network boreholes).

At the Bagnoli brownfield site, Tarzia et al. (2002) (as part of his PhD program with University of Naples Federico II) carried out a study aimed to discriminate anthropogenic pollution sources from natural pollution sources. For this study, heavy metals and Pb isotope data from soils, waste materials, scum, and slag samples from the brownfield site were used. 

Plots of metal concentrations against Pb isotope ratios were extremely useful. For example, Cr values were found to be distributed along two clearly different clusters. One cluster represents the soils of Bagnoli, while the other corresponds to the waste (scum, slag, landfill) material. For decreasing Cr concentrations, the data seem to converge toward soil values. Similar trends are detected for other elements (Fig. 15.9). 

Figure 15.9 Cr versus Mn (A) and As versus Cd (B) concentrations. Such plots show the convergence of data toward natural values (bold arrows) and suggests a relationship between contamination and scum, slag, and landfill materials.

Chemical—structural analysis and leachability tests on scum, slag, and Fe-minerals were carried out to characterize and measure the chemical stability of the metals in waste materials. The investigation was designated to (1) evaluate the... 

From G. Tchobanoglous, H. Theisen, and R. Eliassen, Solid Wastes Engineering Principles and Management Issues, McGraw-Hill, New York, 1977. NOTE Actual removal rates for volatile solids may be less, depending on the amount of material diverted to the scum layer. 

These different types of dirt can be treated using different agents in the washing system warm water for the particles and soluble components, a builder (ion exchanger) for the scum, emulsifying surfactants for the oily materials, a bleach system for the stains, and enzymes for the polymers. As always, you should dream up ideas and questions. 

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