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Fungal and bacterial attack of CCA-treated Pinus radiata timbers from a water-cooling tower
1991 - IRG/WP 1488
Transmission electron microscopy of decaying CCA-treated Pinus radiata timbers from an industrial water cooling tower showed presence of a thick biofilm covering some areas of the wood. The biofilm contained various morphologically distinct forms of microorganisms embedded in a slime. The study provided evidence of the activity of soft rot fungi and tunnelling and erosion bacteria in wood cells. The extent of damage to wood cells due to microbial activity varied, combined fungal and bacterial attack having the most damaging impact.
A P Singh, M E Hedley, D R Page, C S Han, K Atisongkroh

Laboratory culturing and decay testing with Physisporinus vitreus and Donkioporia expansa orginating from identical cooling tower environments show major differences
1996 - IRG/WP 96-10184
Both Basidiomycete fungi Physisporinus vitreus (Pers.:Fr.) P. Karst. and Donkioporia expansa (Desm.) Kotl. & Pouz. were isolated from identical cooling tower environments. Azobé heartwood (Lophira alata), a very durable tropical wood species was totally deteriorated in cooling towers in a similar way by both fungi. First attempts to culture Physisporinus vitreus in laboratory circumstances showed a need for climatic conditions with higher temperatures and higher relative humidity compared to standard conditions known for most Basidiomycete fungi. Moreover there is a supplementary need to alter the acidity of the malt-agar medium and to add a protein nitrogen source like pepton. Identical culturing conditions were supposed for the Donkioporia expansa isolate. However the alteration in acidity is not beneficial for the growth of this cooling tower fungus. High mass loss figures up to 50% were recorded for non-durable wood species inducing wood moisture contents of over 150%, but only a slight growth stimulation on azobé could be observed under laboratory conditions.
J Van Acker, M Stevens

Highly virulent wood-rotting Basidiomycetes in cooling tower timbers
1995 - IRG/WP 95-10125
Over the past ten years most industrial cooling towers changed their water treatment systems in order to meet environmental requirements. Since this alterations wood rot attack has been reported more frequently. Several Basidiomycete fungi were isolated and determined. Amongst the most important ones are strains of Physisporinus vitreus (Pers.:Fr.) P. Karst., Phellinus contiguus (Fr.) Pat. and Donkioporia expansa (Desm.) Kotl. & Pouz.. In situ total deterioration has been reported of highly durable wood species like azobe (Lophira alata), bangkirai (Shorea leavis) and Californian redwood (Seqouia sempervirens) and of CCA-treated softwood, e.g. Douglas fir. The Donkioporia strain was only recently isolated while on lab-scale research is ongoing to stimulate the growth of Phellinus. The growth under laboratory conditions is not evident for these fungi and different parameters affecting growth were investigated. After altering the malt-agar as medium and improving climatic conditions fungal growth of Physisporinus in laboratory conditions on durable wood has been succesful already. Some preliminary results related to the changes in water treatment are discussed.
J Van Acker, M Stevens, V Rijckaert

A light and electron microscopic study of decayed CCA-treated radiata pine (Pinus radiata) wood from a cooling tower
1994 - IRG/WP 94-10056
An inspection of an industrial cooling tower in New Zealand showed surface decay of 12 year old Pinus radiata wood panels treated with CCA preservative to a retention of around 15 kg/m³ of salt. Wood decay micromorphology typical of that caused by soft rot fungi, white rot fungi, 'stripy' and 'v-shaped' erosion bacteria and cavitation bacteria were all commonly seen using a light microscope (LM). Some evidence of the presence of tunnelling bacteria was also seen but was not as common. Soft rot was largely absent from the wettest regions sampled such as spray-line supports and side panels in close proximity to the spray lines, and erosion bacteria attack was the predominant type in these areas. Transmission electron microscopy (TEM) showed that unusual patterns largely consisting of troughs, depression and granulations in wood cell walls, were in most instances, almost certainly caused by erosion bacteria, but in others, tunnelling bacteria were also present. Several decay patterns seen under light microscope as matrices of fine troughs parallel and perpendicular to the cellulose microfibres were difficult to characterise in terms of previous classification but were also thought to have been caused by erosion bacteria. The distinction made by previous classification between patternms formed by erosion and cavitation bacteria needed to be questioned on the basis of observations made. Whilst the TEM showed that erosion and tunnelling bacteria were often present in close association within the wood cell walls, light microscopy suggested that, in the majority of section examined, all the types seen were clearly seperated by regions of undegraded cell wall. The observations underscore the importance of erosion bacteria in wood decay under the conditions of a cooling tower where in-service timbers are kept constantly wet by the spray from water sprinklers. Also of significance is the great diversity of decay types seen, in particular the presence of cavitation bacteria and white rot fungi has not previously been recorded for high retention CCA treated cooling tower timbers.
A P Singh, R N Wakeling, D R Page

Bacteria are important degraders of cooling tower timbers: New Zealand experience
1995 - IRG/WP 95-10128
Microscopic examinations of CCA-treated Pinus radiata timbers in industrial cooling towers in New Zealand showed bacteria and soft rot fungi to be primarily responsible for the decay of these timbers. Of these micro-organisms, erosion bacteria appeared to be most widespread, attacking wood cell walls independently as well as together with tunnelling bacteria and soft rot fungi. Tunnelling bacteria attacked wood often with soft rot fungi, and less commonly with erosion bacteria. Sampling of wood from different locations in the cooling towers inspected indicated erosion bacteria to be most tolerant of oxygen limiting conditions among the microorganisms which attacked the wood, as bacterial erosion was the only type of decay present in the wood constantly saturated with water. The evidence presented of the presence of widespread bacterial attacks of industrial cooling tower timbers in New Zealand is the basis for recognising bacterial importance in the deterioration of cooling tower timbers.
A P Singh, R N Wakeling

Soft-rot in Tabebuia sp. wood used in water cooling tower: identification and degradation capacity of the fungi
1998 - IRG/WP 98-10253
Tabebuia sp. (ipe), a native Brazilian wood, is considered of high natural resistance to decaying fungi, and has been used in harsh environments, as cooling towers. Fifty-one fungi, belonging to mitosporic fungi group (Fungi Imperfecti), were isolated from deteriorated Tabebuia sp. wood samples, collected from the mist eliminator and packing of a cooling tower in operation for about 23 years. The degradation capacity of these fungi was evaluated by soft-rot tests using Eucalyptus grandis and Pinus elliottii wood. The microscopic examination of wood sections showed that Acremonium sp., A. kiliense, Phialophora sp. and Phialophora butyrii caused type 1 soft-rot attack in both mod species, while Fusarium oxysporum, Gliocladium spp., Moniliella-like, Penicillium sp., Pullularia pullulans, Trichoderma spp. and Verticillium sp. were not able to produce the same attack. These results and the analyses of weight loss suggested that Acremonium spp. and Phialophora spp. more important decaying organisms of Tabebuia sp. in the cooling tower.
S Brazolin, M Tomazello, I H Schoenlein-Crusius

Bacteria and wood. A review of the literature relating to the presence, action and interaction of bacteria in wood
1971 - IRG/WP 101
S E Rossell, E G M Abbot, J F Levy

Status of wood preservation industry in India
2005 - IRG/WP 05-30388
The paper traces the history of wood preservation industry in India, listing various mile stones for creation of treating capacity. The preservation industry developed with the development of rail road system on the line of most other developed countries. The most popular wood preservatives are CCA, CCB, ACC, Creosote and recently LOSP have also appeared in the market. The major users of CCA is the Cooling tower industry, which use more than 50% of the current CCA produced in the country. CCB and Boric acid :Borax rule the furniture industry. The use of LOSP is picking up as brush on applications and in the remedial treatments. The overall picture of preservative used (around 1350 tons CCA equivalent) is quite disappointing considering the volumes of non-durable woods used annually 22.5 million m3.
S Kumar

Case study: “Riesenbühlturm”
2017 - IRG/WP 17-20599
In this case study four 7 m long Douglas fir crossbeams were investigated regarding the remaining metal and moisture content. The crossbeams were replaced from a timber tower after 10 years of service in the Black Forest region (South Germany) due to fungal decay. From each of the crossbeams five stem discs were taken and relevant parameters (density, moisture and remaining metal content) were determined at four points (3, 6, 9, and 12 o’clock position). The results confirm the hard treatability of Douglas fir sapwood. Remaining metal content correlates with the performance of the logs, whereby following ranking was found: Eastern crossbeam > Western ≈ Southern > Northern crossbeam Beside this, the results revealed that the highest remaining metal content was determined in discs taken close to the end-grain and -in general- in lower segments (6 o’clock position) of the discs. Furthermore it was found that the applied chromium-copper-ratio can be a useful tool for the interpretation of the remaining metal content vs. metal release. The investigation of the discs enabled the conclusion that the fungal infection started in the transition zone between sap- and heartwood due to core cracks, in combination with a longer period of internal wetness. Afterwards the infection expanded predominantly in a horizontal direction. In order to avoid an early failure of the new installed crossbeams, it was suggested to protect the upper side of the logs by means of stainless steel u-profiles against weathering. A first visual inspection of the covered beams did not show any signs of damages after three years.
E Melcher, J Müller