Biofilm water production systems

Nielsen P.H. (1991), Sulfur sources for hydrogen sulfide production in biofilm from sewer systems. Water Sci. Tech. 23, 1265-1274. 

In some technological and medical applications protein adsorption and/or cell adhesion is advantageous, but in others it is detrimental. In bioreactors it is stimulated to obtain favourable production conditions. In contrast, biofilm formation may cause contamination problems in water purification systems, in food processing equipment and on kitchen tools. Similarly, bacterial adhesion on synthetic materials used for e.g. artificial organs and prostheses, catheters, blood bags, etc., may cause severe infections. Furthermore, biofilms on heat exchangers, filters, separation membranes, and also on ship hulls oppose heat and mass transfer and increase frictional resistance. These consequences clearly result in decreased production rates and increased costs. 

Providing these biofilters only contain beneficial bacteria that are involved in this breakdown of ammonia then they pose little risk to the larvae. If the biosecurity breaks down due to say, operator error, and a pathogen is introduced it may become established in the biofilm with the biofilter and become a more permanent member of the bacterial community. In this situation, there is the potential for the filter to shed pathogens into the water column with subsequent infection of the production larvae. This situation is very difficult to eradicate. Control measures may include installation of UV or ozone after the biofilters to kill any shed bacteria before the water enters the production area or the breakdown and sterilization of the larval production system. 

The other major application for biocides in the oilfield is in biofouling control. This can be defined as the use of a biocide to kill microorganisms that are present in the water that is either injected into an oilfield, or the water that is produced from the oilfield. The reason that biocides are used is to kill the microorganisms before they have the opportunity to attach to the metal surfaces and form biofilms. Considerations on the use of biocides in the injection and production systems are discussed below. 

The sewer processes take place in a complex system. They proceed in one or more of the five phases the suspended water phase, the biofilm, the sewer sediments, the sewer atmosphere and the sewer walls, and by exchange of relevant substances across the interphases. Processes that proceed in the sewer system affect other parts of the urban system, i.e., the urban atmosphere with malodorous substances. Furthermore, wastewater treatment plants and local receiving waters receive not just those substances discharged into the sewer but also products that are the result of the sewer processes (Figures 1.1 and 1.3). 

Biofouling involves the formation of biofilm, whereby hydrated algal- or bacterial-based slimes adhere to water-wetted cooling system surfaces and often contain scales, corrosion products, or other debris embedded within a polysaccharide matrix. The role of biofilms in reducing cooling system efficiency and life span is still imperfectly understood. 

In freshwater ecosystems, particularly streams and wetlands, biofilms account for a large portion of heterotrophic metabolism, as well as primary production (Edwards etal., 1990 see Chapter 12), acting as both sources and sinks for DOM. As the depth of the overlying water in the system increases, attached communities account for a declining share of system metabolism. 

Venkatadri R, Irvine RL. Cultivation of Phanerochaete chrysosporium and production of lignin peroxidase in novel biofilm reactor systems hollow fiber reactor and silicone membrane reactor. Water Res 1993 27 591-596. 

A unique type of corrosion referred to as copper by-product release, cuprosolvency, or blue water occurs in potable water systems constructed of copper tubing, and has been reported worldwide [92-95]. The problem is most often attributed to EPS induced metal concentration cells. The condition is characterized by the release of copper as fine particles in plumbing systems distributing soft water in the neutral or neutral-alkaline pH range. Water may contain between 5 to 300 ppm copper (as Cu +) as finely suspended precipitates. A bacterial biofilm and associated acidic EPS bind copper ions at the metal surface and alter the porosity of the oxide film [96]. Geesey and coworkers [97] characterized binding of an acidic polysaccharide to thin copper films and su ested a cupric ion interaction with carboxyl groups on EPS. These interactions promoted ionization of metallic... 

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