Biofilms sampling

Biofilm study was carried out in the drinking water supply system DWSS"Yovkovtsy , that supply with water the region of Veliko Tamovo, and in the laboratory model of water distribution system. Some experiments were performed 1) to determine microbiological composition of biofilm samples scraped from mild steel or reinforced concrete s main pipe line and concrete tank of DWSS Yovkovtsy 2) to study biofilm formation process on test pipe from PVC, PE, stainless steel and carbon steel in a laboratory model of drinking water distribution system under flow velocity 0,006 cm/s. 3) to study dynamics of biofilm formation process on polypropylene, the pipe material used during the last years in Bulgaria, in a model water distribution system under flow velocities 0.3 m/s, 0.5 m/s, 0.7 m/s and 1 m/s. 

Biofilm samples and microbial contamination of drinking water flowing through the model in result of biofilm formation were analyses with standard methods (APHA, 1992). Number of heterotrophic bacteria (R2A/22°C/7d) coliforms and bacteria from different physiological groups, including corrosion related bacteria were determined. 

Biofilm samples collected from carbon steel and concrete pipes of the DWSS Yovkovtsy had different appearance, content of water, organic and corrosion products, while ones from concrete pipe and water tank s surfaces were the same. Biofilm community mainly consisted of heterotrophic bacteria and some fungi, actinomyces and autotrophic bacteria. Corrosion related bacteria were determined in some of the biofilm samples. 

Comparison between heterotrophic bacteria count in biofilm samples from carbon steel and concrete pipes didn t show significant difference (P=95%) in bacterial density under residual chlorine content in water higher than 0.3 mg/dm3. Below that value, the significant difference in bacterial... 

However, composition of biofilm samples were similar (according to restriction analysis of the 16S rDNA, at this level of differentation) and all three investigated bacterial groups were detected by PCR. Difference was only observed in the intensity of restriction fragments, which may suggest the dominance of different species around the various sampling points. The Article 5 of 98/83/EC Directive allows Member States to set values for additional parameters not included in Annex I where the protection of human health within its national territory or part of requires it so. In our opinion this kind of examinations may be very useful in evaluation of disinfection efficiency. 

The EPRI [1985) survey reveals that a wide range of techniques have been employed in commercially available biofouling monitors including annular flow devices, externally heat tubes, unheated surfaces, condenser simulators, electrically heated wires, biofilm sampling devices and acoustic detectors. 

In addition, cell lysis methods for bacterial biofilm samples and/or other high-biomass samples (such as microbial mats) must be more rigorous than for certain low-cell-densify planktonic communities (such as marine microbes). However, cell lysis must also be optimized for every sample so that the strands of DNA released... 

Table 3 Commercial fouling monitors and biofilm sampling devices...

Biofilm sampling device with removable "buttons."... 

Quintana JC, Idrissi L, Palleschi G, Albertano P, Amine A, El Rhazi M, Moscone D (2004) Investigation of amperometric detection of phosphate application in seawater and cyanobacterial biofilm samples. Talanta 63 567-574... 

Cu Acute toxicity on biofilms EC50 ( C) 20-50 (spring) 100-350 (summer) EC50 (Y) 230 (low P) 718 (highP) EC50 (Fo) 56-92 (low P) 196-206 (high P) Field samples Ter river" Fluvial microcosms Field samples"... 

Side stream sampling devices can be used to collect biofilm and corrosion samples. The biofilm, inorganic passive layers, and metal attacked samples can be characterized with scanning electron microscopy and energy dispersive... 

The decrease of peak numbers was observed, when the spectra of the same amounts of fresh (12 weeks old) and aged (9 months old) mortars were compared. This decrease might be caused by activity of ubiquitous microorganisms that live on the mortar surfaces in biofilms. Especially in mild climate conditions, algae and cyanobacteria [35] can appear here moulds (Aspergillus, Penicillium, Fusarium, Mucor) [36] and bacteria (Arthrobacter Bacillus, Micrococcus, Staphylococcus) [37,38] have been discovered as well. The microorganisms secrete various hydrolytic enzymes that can decompose the organic additives, namely proteins, and make their sample identification less sensitive... 

Bioparticles were periodically sampled and their carbon content measured. The mass of dry biofilm-cells on solid carriers was estimated assuming the following (1) the carbon content is related only to the contribution of biofilm-cells, neglecting the contribution of extra cellular matter (2) the carbon mass fraction of immobilized cells equals the value estimated for free cells, namely 0.44 [60]. 

In addition to sampling in a sewer followed by analysis of specific components or use of a sample for further laboratory or pilot-scale experiments, a number of direct or indirect measurements must typically be performed in the sewer itself. Important measurements related to sewer process studies are DO, reaeration, biofilm characteristics and odor. 

Procedures 1 to 3 described in the previous three subsections have typically been performed on wastewater samples at an upstream point of a sewer. The objective of these procedures has been to characterize the incoming wastewater to the sewer system in terms of COD fractions and process-relevant parameters. Contrary to this, the present procedure number 4 is performed with the overall objective of determining sewer process-related characteristics including the biofilm and reaeration. The characteristics of the water phase considered in procedures 1 to 3 are hereby extended to include all major processes relevant for the microbial transformations in gravity sewers, especially when dealing with aerobic processes. Further detailed characterization that is needed when including the anaerobic transformations will be dealt with in Section 7.2.5. 

Simulation procedure 4 is basically a calibration of the sewer process model for aerobic microbial transformations as described in the matrix formulation (Table 5.3). Both the biofilm processes and the reaeration are included. Initial values for the components and process parameters for this simulation originate from the sample taken at the upstream sewer station. When simulated values of the downstream COD components are acceptable, i.e., approaching the corresponding measured values, the calibration procedure is successfully completed. The major model parameters to be included in the calibration process are those relevant for the biofilm, especially km and K. After calibration, the model is ready for a successive validation process and later use in practice. 

Before dialytic recovery of concentrated analytes, any periphyton or biofilm, carbonate salts, etc., on the SPMD membrane are removed by the following sequence of steps. First, each individual SPMD is immersed in about 200 mL of hexane in a glass beaker for about 20 to 30 seconds. Afterwards, the hexane is discarded. Then, SPMDs are placed in a stainless steel pan and washed with copious amounts of mnning water (tap water is generally used but a 1 L sample should... 

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