Reuse of wastewater has been widespread in this era to support the water sustainability process. Therefore, treated wastewater should be conveyed to suitable places and adopted for different uses. This study presents an empirical relationship between the Darcy-Weisbach and Hazen-Williams equations for four types of pipe material (ductile iron, GRP, concrete, and plastic) by using WaterCAD Version 8i. Two hydraulic models were developed to estimate the head loss in pipes by using different diameters: first, using pipe diameters from 800 mm to 1,200 mm for a flow rate of 1.16 m3/s, second, adopting pipe diameter from 1,600 mm to 2,000 mm for a flow rate of 4.63 m3/s. The study results are the head loss values obtained from the Darcy-Weisbach and Hazen-Williams equations, which were used to correlate them using IBM SPSS Statistics. The correlation coefficient between both equations turned out to be 0.991, 0.990, 0.990, and 0.990 for ductile iron, GRP, concrete, and plastic pipe materials. Additionally, the relationship between head loss and pipe diameter is negatively proportioned for both equations. Also, both head loss equation results are the same. The head loss values in the Darcy’s equation were higher for ductile iron and GRP materials, while being lower for concrete and plastic materials for both models. Selecting concrete or plastic pipes to convey treated wastewater is better than other pipe materials. Another conclusion is that the pipe diameter affects the head loss magnitude irrespective of the kind of equation whether Darcy-Weisbach or Hazen-William equation. Finally, this relationship is very useful for designers in converting the head loss values obtained using these equations.

Introduction. To solve the problem of water shortage for irrigation in the city of Kerbala (Iraq), for the first time, a decision was made to use treated wastewater from urban wastewater treatment plants. Transportation of water from treatment facilities to irrigated lands is carried out through a pipeline in a non-pressure mode. Using the Water Card simulation model, the optimal pipe diameters for two flows, 1200 and 2,200 mm, were selected. The capacity of the existing treatment plant is 1.16 m3/s or 100,000 m3/day, and after the introduction of new treatment facilities, the flow rate will increase to 4.63 m3/s or 400,000 m3/ day. The aim of the work was to experimentally confirm the choice of the optimal diameter of the pipes and determine the hydraulic characteristics of the flow in it. In this regard, in laboratory conditions, experimental studies of the hydraulic characteristics of the flow in a polyethylene pipe with a diameter of 100 mm in the range of slopes (0.005–0.03), with fluid flow in non-pressure, were carried out. Using the theory of hydrodynamic similarity, the results of experimental data were recalculated for pipe diameters of 1200 and 2,200 mm. As field data, when modeling hydrodynamic similarity, the results obtained in the simulation model are taken into account. In world practice, there is experience in the reuse of treated wastewater, but water is supplied to the place of consumption in most cases through open channels. For the first time, pipes of large diameters are used in this work, which requires a more detailed study of the hydraulic parameters of the flow in it. Materials and methods. Using the theory of hydrodynamic similarity, the results of experimentally obtained hydraulic parameters were calculated for plastic pipes with a diameter of 1200 mm at a water flow rate of 1.16 m3/s and 2,200 mm at a flow rate of 4.63 m3/s. Results. Conducting experimental studies and recalculating experimental data from a similar model to a full-scale object (the results obtained using the Water Card simulation model are used as a full-scale object) using the Froude method with similarity coefficients made it possible to obtain the following values of average flow rates, hydraulic friction coefficients λ, Chezy coefficients C, Reynolds numbers and other flow characteristics when filling the pipeline from 0.1 to 0.8 for pipes with diameters of 1200 and 2,200 mm. Conclusions. Conducting laboratory studies to determine the hydraulic characteristics of a polyethylene pipeline with a diameter of 100 mm as a model and substantiate the hydraulic similarity of the model and nature, in the form of plastic pipes with diameters of 1,200 and 2,200 mm, respectively, will allow designing a gravity system of main pipelines for transporting treated wastewater in the city of Karbala (Iraq). Further, the data of the simulation model are used as field data.

Introduction. The study presents an assessment of the economic feasibility of different pipe materials used to transport treated wastewater. The choice was made between pipes made of ductile iron, glass-fiber reinforced polyester (GRP), concrete, and plastic. Hydraulic calculations of operation of an irrigation water supply and distribution system were made using WaterCAD V8i software. Two options of the system operation, that entail different flow rates and diameters, are considered: if the flow rate is equal to 1.16 m3/s and pipe diameters vary from 800 mm to 1,200 mm, and if the flow rate is equal to 4.63 m3/s, and pipe diameters vary from 1,600 to 2,000 mm. Materials and methods. The article analyzes the legal and regulatory documentation on design and construction, urban planning solutions for residential areas, architectural and structural solutions for apartment buildings, statistical and analytical reports on housing construction in Russia, presented on the Internet. Results. Irrigation water represents treated wastewater fed by the wastewater treatment facilities in the city of Karbala, Iraq. Two hydraulic models were designed with account for the above-mentioned costs. Head losses were estimated for each model with regard for all studied materials and pipe diameters using the WaterCAD V8i software and a mathematical model for the purpose of selecting the optimal pipe diameter. Conclusions. A mathematical model was developed to calculate the cost of transporting wastewater in pipes having different diameters and made of four different materials. The ratio of costs to the diameter of pipes, made of four different materials, was identified by developing an empirical equation. The co-authors used the Darcy – Weisbach technique and the Hazen – Williams method to calculate the operating costs with regard for variable diameters, flow rates for the two models, head losses due to friction, annual operation time, annual cost of electric energy, and the energy efficiency of the unit. Thus, a mathematical model was obtained, that can be applied to select the most optimal pipe diameter.

Для решения проблемы дефицита воды на орошение сельскохозяйственных земель в административном округе Кербель в Ираке было принято решение использовать повторно очищенные сточные воды, качество которых удовлетворяет требованиям, предъявляемым для полива воды сельcкохозяйственных культур. Рассмотрены два варианта расходов очищенных сточных вод: со старых очистных сооружений производительностью 1,16 м3/с и второй вариант с расходом 4,63 м3/с с учетом старых и новых очистных сооружений. В работе предпринято обоснование выбора оптимального диаметра и материала труб для обоих вариантов с учетом снижения затрат на транспортировку очищенных сточных вод до места назначения с использованием модели WaterCAD V8i. Выбор производился между трубами из следующих материалов: ковкий чугун, стеклопластик GRP, бетон и пластик. Произведены гидравлические расчеты работы системы подачи воды на орошение. Стоимость транспортировки воды рассчитывалась для каждого диаметра и типа трубы для обоих вариантов. Результаты показали, что диаметр трубы 1000 мм для пластика является оптимальным для первого варианта, а диаметр 2000 мм для материала из ковкого чугуна – оптимальным для второго варианта. Впервые рассматривается вопрос повторного использования очищенных сточных вод для решения продовольственных, социальных и экономических проблем для данного региона и предлагается схема трассировки магистрального трубопровода для повторного использования сточных вод для орошения.