This paper describes an analysis of the effects of adjusting the intensity of filter backwash to the water temperature. The consequences of the lack of such adjustment for the life of filter beds, the amount of water used for backwashing, the amount of energy used for backwashing and the quality of the first filtrate are presented. In order to determine the losses and profits resulting from controlling the intensity of backwash water depending on its temperature, an analysis was carried out at a water treatment plant in southern Poland. Laboratory measurements were used to determine the granulation and specific gravity of sand grains filling the filtration beds. On the basis of measurements on a semi-technical scale, the magnitudes of filter bed expansion were determined for average monthly wash water temperatures. They were first calculated from the Richardson–Zaki equation, using different formulae for the value of the exponent of the power in this equation. Due to significant differences in the density and shape of grains covered with a permanent deposit after several years of filter operation, a satisfactory match between the formulae known from the literature and the results of expansion measurements was not obtained. Therefore, an new formula for the bed expansion was developed based on the Richardson–Zaki equation. A good fit of this formula to the experimental results was obtained. Monthly average values of water temperature were compiled, and on this basis the required amount of backwash water and energy was computed. The computations were made for 25% of fluidized bed expansion. Possible energy and water savings were estimated, as well as further gains from keeping the required expansion of the porous bed constant regardless of the wash water temperature.

The impact of a storm water storage tank outflow construction on its required volume is discussed. A dimensioning of the tank by a rational method applied for small sewerage systems is presented. For large systems, subroutines should be developed to take into consideration the construction details of complex storage tanks in the software enabling real time modelling of sewerage systems. Such subroutines can be tested under simple conditions using rational methods of sewerage modelling, including the approach described in the paper. In the example discussed here for two different positions of the sewer delivering to and collecting stormwater out of the tank both the tank required volume and the outflow as a function of time visibly depended on the sewer position. This was proofed for a rectangular chamber storage tank of the same bottom surface area. However, if the bottom surface area and the storage tank height were calculated in such a way to enable the same maximum value of an outflow from the tank for two different positions of the sewer both the tank volume and the outflow as a function of time were proved to be very similar. Concluding the tank volume depends visibly on the construction of outflow, but the height of the tank can be adjusted in such a way to keep the same maximum outflow for different details of the outflow construction. After this adjustment, the volume of the tank was proved to be almost independent of the construction of outflow from the tank.

The objective of the study is to recognise whether epoxy resin or polyurethane internal linings of ductile iron (DI) pipes create visibly smaller head loss in flow than cement mortar linings. Some data reported by the Ductile Iron Pipes Research Association (DIPRA) was used in the calculations. Only the data from hydraulic tests performed no later than 30 years after the placing of the mortar lining were considered. The average values of the Hazen–Williams roughness coefficients C for each of the internal pipe diameters were calculated, and single experimental data neglected. Two different approaches were taken for interpreting the DIPRA experimental results and omitting the fact that the flow rates during these tests are unknown. The Hazen–Williams roughness coefficients C were used in both for computing the friction factor f from the Moody chart for three values of flow rate: being equal to the optimal value for a given diameter, and then by 50% larger and 50% smaller than this value. Next, the computed friction factors were compared with the values predicted from the Moody chart for smooth pipes. In the first approach, the friction factors f were computed using the Epanet2 software, and in the second approach, a general equation for calculating f from known C and flow parameters was applied. Both approaches resulted in friction factors f very close to those for smooth pipes for the whole range of Q. In conclusion, more smooth plastic linings of DI pipes do not result in a significantly more visible saving of energy for pumping.

This article presents a literature review of energy consumption in water treatment and distribution systems. At the global level, electricity consumption for water treatment and distribution is discussed in relation to total electricity generation. Available data on the energy efficiency of water treatment plants are reviewed. Potential measures for reducing energy consumption in pumping stations, water distribution networks, and water treatment plants are identified. The paper also highlights literature sources providing data on the structure of water distribution systems serving settlements of different sizes, allowing the analyzed water supply system to be compared with other existing systems. An example is presented to demonstrate that the condition of a water distribution system may be incorrectly assessed when hydraulic calculations are based exclusively on flow rate and pressure measurements obtained from a network with unacceptably high water losses. Particular attention is given to the rapid gravity filtration process, with a focus on reducing the energy required for filter backwashing by adjusting the backwash intensity according to the temperature of the backwash water. This approach allows the backwash intensity to be reduced during winter, thereby minimizing filter media loss during backwashing. The resulting energy and economic benefits of this adjustment can be quantified. The paper further describes an energy-efficient control strategy for a filtration plant and discusses its optimization from an energy perspective. It also explains why the effects of implementing such a control strategy cannot be predicted a priori without empirical investigation. Finally, an example of the practical application of this strategy is presented.