I belong to the operations team particularly the boiler dosing, water treatment system and the laboratory department. I would just like to ask an opinion and if there's any solid references which I could read regarding the proper dosing location of phosphate particularly sodium tripolyphosphate.
Here in our plant the dosing is located at the economizer inlet. It has also been emphasized that polyphosphates must not be fed to the boiler feedwater line when economizers, heat exchangers, or stage heaters are part of the preboiler system.
As presented by one of the references by Byworth Boilers: where an economizer or feedwater pre-heater is used they should be dosed directly into the boiler shell, this is to prevent deposition on the heat transfer surfaces.
The information which I have are contradicting to the location of dosing point here in our plant which is at the economizer inlet. Can someone help me with this concern? So that I could address it also to our management and do some necessary revisions if there's any solid information I could share to them.
Hoping for a positive response. I worked in an Ammonia plant that produce High pressure steam barg. Posted 25 May - AM. Phosphate dosing had a significantly stronger effect on bacterial than on fungal communities on both type of materials lead and PVC. Lead favoured bacterial diversity, while phosphate reduced it and increased fungal diversity in biofilms. The combined presence of phosphate and lead materials favoured the appearance of microorganisms specialized in phosphorus metabolism and metal resistance.
Some of these microorganisms have bioremediation capabilities, therefore can be used to promoting a protective environment inside the pipe. Showing that lead promoted a more diverse bacterial community than PVC and that phosphate reduced bacterial biofilm diversity in both type of materials, while increasing fungal diversity.
Therefore, it can be concluded that phosphate variation can induce changes in the structure of biofilms and affect the level of chlorine in the water, impacting the disinfection strategies where a chlorine residual is kept safeguarding water safety. This new knowledge is of great relevance for water utilities to improve management strategies and inform decisions to control microbial growth in drinking water pipelines. In order to study the development of microorganisms under different doses of phosphate, three drinking water biofilm reactors DWBR were designed and assembled for each experimental case Fig.
To connect all the parts of the bioreactor, a black PVC flexible tubing inner diameter: 9. The water used for the experiments was the local drinking water supply, where the water is treated with ferric sulphate at treatment level as coagulant and monosodium phosphate is used to minimise lead dissolution during distribution. The pre-treatment tank was built in a higher elevated position than the tank connected to the DWBR to favour the transport of water between the two tanks , and a diaphragm pump was added to ensure that all the water in the tank passed through the filter bag containing the iron pellets.
V, Nieuwegein, Netherlands. GEH pellets have a size of 0. During the 28 days of the experiment, several physicochemical factors were analysed daily for the water in the three DWBR as well as the local drinking water feeding them. Every analysis was performed in triplicate and the average of the replicates was calculated.
In addition, triplicate bulk water samples were collected weekly, and analysed for total lead, total iron, orthophosphate, total phosphorus and total organic carbon by an accredited drinking water laboratory, ALS environmental Coatbridge, UK. Then coupons were brushed using toothbrushes to remove the biofilm attached to the coupon surface as described in Deines et al. The biofilm solutions were filtered through a sterile filter 0. The PBS solutions with the biofilms were filtered through a sterile filter 0.
The procedure for extracting DNA was based on a modified protocol described by Douterelo et al. For fungal characterisation, the ribosomal internal transcribed spacer regions ITS were targeted. On day 28, a lead coupon and a piece of PVC tubing were taken from the high phosphate and low phosphate experimental bioreactors for visualization with SEM by the Electron Microscopy Facility of the Faculty of Science of the University of Sheffield.
R statistic values from the MDS analysis indicated the strength of the impact that the factors had on the samples 73 , in this case treatment high phosphate, control phosphate, low phosphate and material lead and PVC. R values vary between 0 and 1, where 1 indicates high separation of the samples between levels of the factor and 0 indicates no separation Alpha-diversity metrics and the relative abundance of the most representative taxonomic genera for bacteria and fungi were used as microbiological parameters in the establishment of correlations.
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Rodriguez, M. Spatial and temporal evolution of trihalomethanes in three water distribution systems. Tsagkari, E. Contrary to these results, other studies in drinking water related systems, reported an increase of cells in biofilms developed under different phosphate treatments Fang et al.
An explanation for these contradictory results might be that these studies were performed using annular bioreactors Fang et al. Besides, previous studies have shown that the addition of phosphate in drinking water can reduce the synthesis of EPS by biofilms Fang et al.
Therefore, microorganisms grown under higher phosphate conditions might produce less EPS, thus favouring a weaker biofilm structure, with less capacity of adhesion and more sensitive to external forces and chemical agents.
This could explain the results from this study, where a lower number of cells was observed in biofilms exposed to phosphate treatment. Considering this results, phosphate can promote structurally weaker biofilms that can be easily removable and mobilised into the bulk water, but increasing the risk of discolouration and the presence of opportunistic pathogens at tap level Douterelo et al.
According to the results found in this experiment, there were not significant differences between the bacterial communities in the two experimental conditions Figures 6A,C. However, the increase in phosphate tended to reduce bacterial richness, whilst promoted bacterial dominance, thus fewer OTUs were predominant in the community.
This finding contradicts those of Payne et al. Similarly, Jang et al. Despite phosphate has been considered one of the main factors that can affect bacterial distribution in DWDS Douterelo et al. Nevertheless, phosphate did affect the structure of fungal communities Figure 6B , suggesting that this chemical can be a limited nutrient for these organisms in DWDS. Little is known about phosphate effect on fungal populations in DWDS, but fungi are known to form symbiotic associations with most plants and release mineral nutrients, specially phosphate Smith and Read, In this research, under both experimental conditions, we found several bacterial and fungal genera with members able to solubilize and accumulate phosphate.
For example, bacteria like Acinetobacter , Herbaspirillum , Pseudomonas , Rhizobium , Klebsiella or Xanthomonas , and some fungi including Alternaria , Cladosporium , Penicillium or Fusarium have been identified as phosphate solubilizers Sidat et al.
In this study, the whole metagenomics data showed differences in the most represented functional traits between the two phosphate conditions tested Supplementary Figure 2. In control samples, sequencing reads associated to nitrogen metabolism were predominant, whilst sequences related to ATPases, ion transporters, and DNA-interact proteins were highly abundant under phosphate treatment.
This suggests that the addition of phosphate might change the genetic composition of the biofilm communities, thus affecting functional traits. The high relative abundance of sequences related to nitrogen metabolism within biofilms in this study was not expected, since autotrophic nitrifying organisms bacteria and archaea are highly found within chloraminated DWDS Wilczak et al.
It must be noted that in this study both the relative abundance of phosphate metabolism related sequences and the presence of microorganisms able to accumulate phosphate was low.
Despite that the phosphate concentrations used in this study did not trigger important functional changes, longer dosing periods i. Similarly, research based on gene expression using RNA sequencing instead of DNA would help future studies to identify specific active functional traits involved in phosphate metabolism.
This study has yielded new information regarding the impact of phosphate dosing to control plumbosolvency on biofilms within DWDS. The following conclusions can be drawn as a result of the research:. Increasing the phosphate dose triggered a reduction in biofilm cell numbers and promoted a less consolidated and poorly distributed biofilm structure. Phosphate enrichment in drinking water did not significantly affected bacterial community structure, while influenced the composition of fungal communities.
Bacterial communities were more diverse and richer over time when compared with fungal communities. Sequences related to nitrogen metabolism mainly in amino acids synthesis and ribosomal proteins were predominant in control samples, whilst phosphate enrichment promoted the presence of sequences related to ATPases, ion transporters and DNA-interacting proteins.
The datasets presented in this study can be found in online repositories. ER and GD performed the flow cytometry analysis and analysed the results. CC participated in the corrections of the manuscript. All authors contributed to the article and approved the submitted version.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. We thank Yorkshire Water and in particular Jessica Lindquist and Jenny Banks for advice on phosphate dosing and for providing equipment to measure physico-chemical parameters.
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