Treatments with Biocides

Treatments with Biocides Previously Fractured Formations 

A special problem is the refracturing of a previously fractured formation that is contaminated with bacteria. In such a case the fracturing fluid must be mixed with an amount of biocide sufficient to reach and to kill the bacteria contained in the formation. The refracturing of the formation causes the bactericide to be distributed throughout the formation and to contact and kill bacteria contained therein [1181]. 

This process reduces the amount of control biocide employed in the control of contamination of oil production system waters by sessile bacteria. The biocide may be applied at intervals of 2 to 15 days. The duration of biocide application is preferably from 4 to 8 hours [1244]. 

Chemical treatments for bacteria control represent significant cost and environmental liability. Because the regulatory pressure on the use of toxic biocides is increasing, more environmentally acceptable control measures are being developed. 

Besides adding biocides to wells, another approach seems to be promising— modifying the reservoir ecology. The production of sulfide can be decreased, and its concentration is reduced by the establishment and growth of an indigenous microbial population that replaces the population of sulfate-reducing bacteria. 

---

The continuous recirculation and spraying results in dirty water building up in the sump. In order to reduce the incidence of infection to occupants and fouling of the nozzle, water treatment with biocides and softening of the water supply are required. The sump is complete with strainers in a position which allows easy access for cleaning. See Fig. 9.15. 

Treatments with Biocides Previously Fractured Formations... 

The most common cause of deposits in polymer/product preparation, filtration and dosing equipment is bacteria. Waterborne bacteria can thrive in make-up systems, causing slimy or pseudoplastic deposits to form. Once this has been identified, the systems need to be thoroughly cleaned, pipe work replaced and a treatment with biocide implemented. Care needs to be taken with the choice of biocide, it must be fuUy water soluble and compatible with the polymer/product otherwise reduced performance will result. 

Before any remedial action can be taken, it is necessary to identify the t) e of bacteria involved in corrosion. Aeration of water in a closed recirculating system reduces the activity of anerobic bacteria. Chlorination and treatment with biocides help control populations of some bacteria, though they are not effective in all cases. Also, the bacteriocides fail to reach the areas underneath deposits where the bacteria thrive. Coating a buried structure with tar, enamel, plastic, or the like is often an effective means to... 

The treatment with biocides is normally done by depositing the active ingredients in the wood by vacuum or pressure. 

Recommendations were made to begin treatment with corrosion inhibitors and to make system operation changes to reduce grease and oil fouling. Other water chemistry recommendations involved reducing the amount of aggressive anion in solution and pursuing biocidal treatment. 

Significant microbiologically induced corrosion due to the presence of bacteria in the water is evidenced by saucer-shaped pits, smooth sided pits, bright shiny copper to matte red clean areas. The black deposits, corrosion products from carbon steel, may cause underdeposit corrosion and may cause the failure. Treatment of the water with biocide may minimize microbiologically induced corrosion. 

In contrast to the case of HMPC, most lipases hydrolyze the racemic acetate of CPBA 9 to give a mixture of the insecticidally active (S)-CPBA 2 and the (R)-acetate 1J). Thus, the desired (S)-CPBA J2 could be separated from the (R)-acetate 10 by means of a continuous counter-current extraction using n-heptane solvent at 80°C. However, it is important to utilize the recovered (R)-acetate W for an efficient process. Fortunately, since the proton of the asymmetric carbon of the cyanohydrin acetate is labile, the antipodal (R)-acetate is easily racemized by treatment with weak organic base such as triethylamine without any side reactions. The racemized acetate J9 thus obtained was recycled as shown in Figure 6. Therefore, all of the racemic acetate 9 was converted to the desired (S)-CPBA 2 in this recycling process. The (S)-CPBA 2 obtained was esterified with (S)-2-(4-chlorophenyl)-3-methylbutyryl chloride to produce the most insecticidally active stereoisomer V2 of fenvalerate, namely esfenvalerate. The relative biocidal activities between... 

As mentioned previously, oxygen controls the corrosion rate in the neutral pH range, if the oxygen is less than 1 ppm, the penetration rate in carbon steel or cast iron will be less than 1 mpy (0.025 mm/y) at room temperature, provided no corrosive bacteria are present. If corrosion-inducing bacteria are present, treatment with a biocide such as chlorine is imperative. In theory, because freshwater can be treated, carbon steel exchanger tubes can be used. However, control of water treating equipment is sufficiently difficult and... 

Fig. 1 Time survival kinetics for the inactivation of a bacterial population by treatment with a chemical agent. The D-value represents the time taken, at a given concentration of biocide, to reduce the surviving population by 90%.

The problem of bioactivity can be reduced or eliminated by the use of biocides. There are different types of biocides and one must be aware of the toxicity level of these to decide the most suitable biocide for that application. Already affected systems can be treated with biocides but it is very difficult to release the biofilm once it is formed. In that case a biocide treatment... 

The results on Table 2 shows a Methylene Bisthiocyanate based biocide. The mechanism of action of this biocide is to block the transfer of electrons from primary cytochrome dehydrogenase, and thereby cause an uncoupling of oxidative phosphorylation . Here the Total ATP results initially increase on treatment with the biocide a small increase in Free ATP is also evident along with a reduction in viable counts. With time there is a reduction in Total and Free ATP along with a further reduction in the plate count results. 

Various incidents of pollution have been reported from industrial waste, effluents from sewage treatment plants, food processing plants along with biocides and toxic effluents from sawmills and timber processing areas. These effects are often enhanced by disposal of hazardous wastes in municipal landfills. 

SEM images show that silicone has filled and sealed the inter-monofilament pores and voids and indicates that the PEG silicone surfactants coating the fabrics were decomposed after plasma treadnent. The cleaved products coating the nylon fabric appear to be distributed very uniformly. This phenomenon is consistent with the results of the contact angle measuranents cleavage of the prepared surfactants leads to water-insoluble silanol moieties and two water-soluble products this process imparts excellent water repellency to the nylon fabric. Zhang et al. (2003) determined antibacterial properties qualitatively through measurements of areas from which S. aureus and K. pneumonia have been eradicated. The silicone coat at the eradicated area is not transparent. Biocidal treatments with both the silicone and PEG 2000 silicone surfactants improved the antibacterial properties of the nylon fabrics. The results we obtained before and alter plasma treatment were similar, especially for S. aureus. Thus, the sample treated with PEG 2000 silicone retained its antibacterial activity and water repellency after plasma treatment (Lin et al., 2006). 

As mentioned earlier, larval feed companies, for these reasons, have developed specialized products which contain bacteriostatic agents to keep bacterial loads within acceptable levels. These include specially treated cysts, enrichment products with bacteriostatic properties, or separate formulations which can be added to the Artemia hatching or enrichment medium. Also at the research level, several attempts have been made to disinfect Artemia nauplii (e.g. Gatesoupe, 2002 Tolomei et al., 2004 Gimenez et al., 2006). These include treatment of either cysts or the hatched nauplii with biocides (e.g. formaldehyde), UV, ozone or peroxide-based products. Apart from the fact that these treatments might cause considerable mortality to the nauplii or reduce their vigour, they might also pose potential risk to the predator larvae they are fed to, because of residues or toxic by-products produced due to these treatments. 

The impact of each biocide on microbial populations, together with the compatibility studies, can be used to select the most effective biocidal treatment. The biocides are first evaluated for their ability to inhibit metabolic activity at the time of maximum growth activity this maximum time is determined from growth curves of the microbial populations of the formation and river wastes. Growth curves are then measured for the selected biocide(s) at different concentrations to determine the optimum level of biocide required and the period necessary for alternate slugging of the injection waters. The biocidal treatment is then determined from the growth-concentration curves and the compatibility studies. 

For potable water applications, only off-line treatment with DBNPA is recommended. This is to ensure that the single produce active concentration (SPAC) of 90 ppb of DBNPA in the permeate is not exceeded. Sodium bisulfite and other reducing agents can decompose the active ingredient in DBNPA formulations. Hence, it is recommended to suspend use of reducing agents during addition of DBNPA to avoid decomposition of the biocide. ... 

HjS. This change may result in potential SSC and other cracking mechanisms. Sulfate-reducing bacteria (SRB) activity in the water phase is the primary cause of the H2S increase. As a result, chemical treatment with a biocide may be required. 

---