Accumulation of loose deposits in pipe segments K.Neilands , J. Rubulis and M.Bernats

1. Accumulation of loose deposits in pipe segments K.Neilands, J. Rubulis and M.Bernats Department of Water Engineering and Technology, Riga Technical University, Latvia kaspars.neilands@rtu.lv, janisrubulis@gmail.com Objectives & Approach Discolourations of drinking water is second most often described complain from consumers in water industry after the interruption of water supply. Particles from drinking water network can be washed-out using uni-directional flushing (UDF) method. The aim of this study was to calculate the amount of loose deposits from cast iron pipe segments during several UDF campaigns. Figure 3. Flushing of 400 mm cast iron pipe Figure 2. Online measuring equipment used during UDF campaign Siemens SITRANS FN MAG 8000 and Ultraturb ™ with controller sc100™. Figure 1. Discoloured water from tap Conclusions The measured online turbdity during UDF can be used as a tracer and applicable to calculate the accumulated sediment quantity in pipe segments. The amount of loose deposits washed-out from cast iron pipes varied from 0.07-0.69 kg/m measured as suspended solids. The average velocities of flushing ranged from 0.2-2.34 m/s and shear stress 0.43-2.05 N/m2 acting on pipe walls. The crystalline phase analyzes showed predominance of quarz and goethite in loose deposits. Knowledge of the sedimentation processes depending on temporal variations of daily velocities and the influence of irregularities of pipe layout on accumulation procees of loosed deposits is object for ongoiing study. Methods Figure 6. Mass of accumulated and during UDF actions washed-out loose deposits was calculated assuming conversation relationship proposed by Boxall et al. (2006). The concentrations of loose deposits per meter of pipe were observed from 0.05kg/m till 2.4kg/m. Results showed that flow velocity of flushing and daily hydraulic regime are the key factors for accumulation of loose deposit amount in pipe segments. Figure 5Turbidity curve obtained with online equiment for flushing route 4 Figure 4. Layout of flushing routes for cast iron pipes of Ø 200-400 mm (AutoCAD 2005). The UDF actions are performed in the numbered order. Results Fouling of drinking water distribution system pipes is serious problem, which causes discoloration to consumers. Figure 9. Effect of water velocity in pipe segment during UDF and total washed-out mass of loose deposits for pipes Ø 100-300 mm. Figure 8. Mass of calculated loose deposits and flushing velocity in individuals pipe segments during UDF campaign for pipes Ø 100-300mm. Figure 9. Calculated concentration of loose desposits per meter of flushed pipe from route 4 Figure 7. The stereomicroscope image of loose deposits washed-out from drinking water networks with predominantly dominated quarz and goethite. Bar 500 μm. References Boxall J. B., Saul A.J., GunsteadJ.D. and Dewis N. (2003) Regeneration of discolouration in distribution systems. Proc. ASCE, EWRI, World water and environmental resources conference, Philadelphia, USA