Biostatic

A comprehensive analytical program for characterising wastewaters should be based on relevance to unit treatment process operations, the poUutant or pollutants to be removed ia each, and effluent quality constraints. The qualitative and quantitative characteristics of waste streams to be treated not only serve as a basis for sising system processes within the facility, but also iadicate streams having refractory constituents, potential toxicants, or biostats. Such streams are not amenable to effective biological treatment, as iadicated by the characterization results, and requite treatment usiag alternative processes. 

Biostat. This is also known as a turbidostat. It is a system where cell growth is controlled and remains constant while the flow rate of fresh media does not remain constant. Cell density is controlled based on set value for turbidity, which is created by the cell population while fresh media is continuously supplied. A turbidostat is shown in Figure 5.8. 

In a chemostat and biostat or turbidostat, even with differences in the supply of nutrients and/or fresh media, constant cell density is obtained. The utilisation of substrate and the kinetic expressions for all the fermentation vessels are quite similar. It is possibile to have slight differences in the kinetic constants and the specific rate constants.3,4 Figure 5.9 shows a turbidostat with light sources. The system can be adapted for photosynthetic bacteria. 

The continuous cultures of chemostat and biostat systems have the following criteria ... 

The experiment is accomplished with a 2 litre B. Braun fermenter biostat (Germany) equipped with DO and pH meters. Temperature and level controllers are very sensitive, with highly accurate response from the sensors installed in the vessel. Figure 10.7 shows a perfect continuous fermentation set up used in photosynthetic production. A small modification of... 

Fig. 10.7. A complete laboratory set-up of biostat, B. Braun fermenter with external feed pumps and product reservoirs.

The batch experiment had neither incoming fresh media nor any product stream leaving the fermentation vessel. A complete experimental set up with a B. Braun Biostat, is shown in the above laboratory experimental set up. The continuous flow of media requires a feed tank and product reservoir. The batch process has many disadvantages such as substrate and product inhibition, whereas in the continuous process the fresh nutrients may remove any toxic by-product formed. 

Citric acid fermentation of cane-molasses is by submerged fermentation in a 21 biostat (B. Braun) stirred fermenter. A strain of Aspergillus niger is the most widely used for commercial production. A. niger is also highly recommended in the present study, which can obtained from the American Type Culture Collection, Rockville, Maryland, USA. Molasses... 

Prepare spores, fungal conidia/small pellets in Petri dish or cotton-plugged flask, for 48 hours. Harvest the spore in separate flask with media for propagation. Once in the separated flask the concentration of spores has reached to about 3 million per litre. It is now ready to be transferred to a 21 B. Braun biostat fermenter. The minimum volume of harvested spores in the flask is 300 ml. Media must be prepared based on sufficient carbon source... 

Prepare seed culture and use it for inoculation of 21 airlift and 21 B. Braun biostat B using soluble starch or glucose. 

Because of their surfactant and filming properties fatty amines such as coco-alkylamine acetate (and more especially diamines, such as tallow propylenediamine) are also occasionally employed in other types of water treatment programs. For example, they may be used as corrosion inhibitors for steel cooling systems, especially those smaller units where minimal operational control is provided. The amines must be continuously dosed to ensure good film formation (and thus corrosion protection), typically at 5 to 10 ppm active amine. They also tend to have good biostatic control properties, which provide a benefit of algal and bacterial control at no extra cost. 

These same diamine materials find further application in, for example, formulations for mussel and barnacle control in large once-through, condenser cooling systems, as corrosion inhibitors and biostats for hydrostatic testing of oil and gas pipelines, and as corrosion inhibitors in food industry retort cookers. 

Production strains are stored in a dormant form by ai r of the standard culture preservation techniques. Thus, a spore suspension may be mixed with a sterile, finely divided, inert support and desiccated. Alternatively, spore suspensions in appropriate media can be lyophilized or stored in a hquid culture biostat. 

J. R. Brennan, S. P. Gebhart, and W. O. Blackard, Pump-induced insulin aggregation A problem with the biostator, Diabetes, 34, 353 (1985). 

BioWave 50SPS bioreactor (Wave Biotech AG, Tagelswangen, Switzerland) (since recently distributed by Sartorius BBI Systems GmbH, Melsungen, Germany, as Biostat Cultibag RM 50 )... 

Borenstein, M., Hedges, L., Higgins, J., and Rothstein, H. 2005. Comprehensive Meta-analysis Version 2, Biostat, Englewood NJ. http //www.meta-analysis.com/... 

Borenstein, M., Rothstein, H., and Cohen, J. (2000) Powet and pte-cision a computet ptogtam for power analysis and confidence intervals. Biostat, http //www.Power-Analysis.com. 

Life Science Inst., Miles Lab. (USA) Biostator GCIIS up to 27.5 mM 50 hours... 

Amines/diamines have both surfactant and biostatic properties and are therefore particularly useful for systems that are subject to fouling. 

In general, the continuous, biostatic, slow-release bromination of smaller comfort cooling systems is also both practical and cost-effective. But it is the rationale for routinely recommending periodic applications of relatively expensive nonoxidizing biocides to cooling systems of any size, without benefit of proof of need, effectiveness, or program costs, that should be questioned. 

The concept of dispensing biocides or biostats in tablet form has recently been extended to the supply of certain nonoxidizers, such as 2,2-dibromo-3-nitrilopropionamide (DBNPA) (which has been widely available for many years as a liquid product and to a lesser extent as a powdered product). 

In general, the solid materials tend to act as biostats rather than biocides. Programs that use biostatic control in partnership with periodic applications of nonoxidizing biocides have proved to be extremely effective in many comfort cooling and general industrial cooling systems. 

NOTE Products exerting a biostatic effect are usually continuously present in cooling water at a low level (say below 0.5 to 0.6 ppm actives) and have an inhibiting effect on the proliferation of microbiological flora but do not reduce current populations. 

Biocide/biostat programs based on sodium bromide oxidation provide a much safer option to cooling system operators than gaseous chlorine and a lower cost option compared with the addition of bleach (also the total volume of liquid consumed is decreased compared with bleach). 

Good quality manual valves, or possibly with suitable automatic valves and a timer system, in which case, it is possible to provide periodic biocidal shock treatments rather than continuous background, biostatic conditions. 

Since their widespread introduction in the early 1980s, hydantoin-based biocide/biostat programs have been favored by many operators for application in a wide variety of general industrial and commercial cooling systems. There are several reasons for this, including ... 

Fourth, the concept of a background bromine biostat, coupled with a flexible nonoxidizing biocide program, has provided the basis for clean cooling systems, with minimal biofilm formation and algal slimes. 

Many of the nonoxidizing biocides employed in cooling systems today were originally developed for other applications, such as slimicides for pulp and paper, biostats for cosmetics, or sanitizers for food factories. The experience gained for these applications has proved to be useful for cooling water systems. Some products that have been available for several years have been, or are being, launched into new and different markets, especially where environmental concerns have a high profile. 

In order to provide a biostatic effect for any particular organism, nonoxidizers are required to be present at a certain minimum inhibitory concentration (MIC), and for a biocidal effect, at a minimum kill concentration... 

Apart from ready-to-use biocide formulations, there are also other chemicals that exhibit a degree of microbiological control, such as certain corrosion inhibitors that have a biostatic or biocidal action, for example, chromate. 

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