Rapid Sand Filter is one of the most important units in the water treatment plants. It has some difficulties in operation such as backwashing. For the solving of this problem a rapid Sand Filter has designed and built with the self-cleaning backwashing system. This system consists of 3 main constituents; one galvanized siphon and two galvanized steel tanks. One of them is used for filtration and the other used for the storage of filtrated water in elevation for backwashing the system. Water enter from upside of the Filter through the inlet pipe, and collected from the under drainage pipe. Then Filter water conduct to the storage tank and exit from outlet pipe. In the beginning, the head loss was low, but because of bed clogging by suspended solids; it increases gradually to the designed head loss (1.2m). Then the system is outed of the service automatically and the backwash is began. The main data for the design of system selected from the hydraulic rules of siphons and rapid Sand Filter criteria. After essential calculations it was constructed and was started operation. For the hydraulic studies a known volume of storage tank was selected and the time needed for the fill (in filtration stage) and empty (in backwash stage) of water volume with volumetric method were measured.In hydraulic studies the Filter surface rate (SOR) was selected about 5-7.5m3/m2/hr (1.39-2.08 lit/sec) and the flow of water in siphon, during the backwashing was measured 8.7 lit/sec. It can be seen that the siphon passes 4-6 times the inlet raw water thus a negative pressure will created in the siphon which causes the water above the Sand bed to be discharged automatically and rinse water from elevated tank flow under the Sand bed and back wash it.So according to this study self cleaning rapid Sand Filter is very useful for water filtration, especially in small population community. The construction of system is rapid, simple and economic.

Granular media including rapid gravity Sand Filters are used in water and wastewater treatments. When Sand Filters are clogged due to deposits of particles and particul-bound pollutants, it will lead to head loss and under this situation it is necessary to perform Filter backwashing. Prediction of Sand Filter head loss is the major focus of this study. To meet the primary ojective of this study, a single-layer rapid gravity Filter with Sandy media was tested with inflow water containing different concentrations of lead (Pb). The amount of deposited sediments and the resulting head loss were simulated in the Filter media by combination of Karman-Cozeny, Rose and Gregory equations under different discharges. The maximum time to reach the various amounts of head loss was obtained when the inflow lead concentration was lowest (25 ppm) and the surface Filter leading was the highest (6. 22 m3/m2/hr). The highest lead removal efficiency (92%) was obtained when the input lead concentration was 25 ppm and Filter surface loading was 3. 11m3/m2/hr. Comparing the specific head loss under different operating condition it has been shown that the time difference is less under lower head losses of 5 and 7 centimeters. In addition, the slopes of filtration discharge under similar operating condition showed to be steeper verifying a higher filtration performance when the concentration of input lead and Filter surface loading was lower.

The use of drip irrigation systems in agriculture is associated with several problems. Clogging of Filters and drippers and, thus reducing the uniformity of water distribution needs to be addressed. Proper design and construction of the Filter can be one of these suitable solutions to the problem. In this study, a physical model including a Filter tank with a height of one meter and a diameter of 60 cm for placing Sand with different Sand size and thickness of different layers along with a pump, a power of 0.5 horsepower to provide pressure, two pressure gauges were used to determine the hydraulic load losses in the Sand Filter and, raw water of specified quality. 9 treatments of granulation and layering and, two treatments of water quality containing the amount of suspended solids were used. The aggregation of these treatments was 1.77, 0.89, and 0.45 mm, respectively. The results showed that the load loss changes in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45–0.89 mm. the load loss increased with the smaller particle size of Sand. The results showed that the percentage change of filtration in the granulation range of 1.77 - 0.89 is less than the range of 0.45 - 0.89 mm and with increasing the height of the middle layer, the percentage of filtration of Filters increased. The results showed that the percentage change of filtration in the granulation range of 0.89 – 1.77 mm is less than the range of 0.45 - 0.89 mm. The percentage of filtration increased with increasing the height of the middle layer. But, the changes in the percentage of filtration for changing the height from 12 to 17 cm were more than the changes in the percentage of filtration from 17 to 22 cm. Clay particles, plant debris, insects are water-soluble substances that must be refined by Filters for drip irrigation.

"Schmutzdecke" is developed by particle deposition of a few centimeters deep on the top of the Sand layer in slow Sand Filters. It plays an important role in removal mechanisms and is responsible for the significant increase of head loss during operation. After several weeks of Filter operation, the surface area of the bed becomes clogged due to deposition of suspended solids. Cleaning of the bed top is required when the final head loss occurs. Since the operation costs of slow Sand Filters depend on cleaning intervals, the operation cost decreases by increasing the time of filtration run. The objective of this study was to evaluate the effect of bed top layer mixing on Filter performance. Two experimental pilots (one test and one control) were built from 240 mm PVC pipe 170 cm high. The Sand media depth in each Filter was 60 cm with a uniformity coefficient of 2.3 and effective size of 0.2 mm. During the 149 days, 30 cm of the top layer of the test Filter bed was mixed every other day and Filter performance was evaluated and compared with the unmixed control Filter. This research indicated that the rate of head loss decreased with bed top layer mixing and that filtration run increased to more than two times the typical value without notable effects on effluent quality.

The continuous Filter is a kind of Sand Filter, which will operate without any interruptions for backwashing and also it accepts high-suspended solid levels in feed stream. Fouled Sand is continuously removed from the Filter bed, washed and recycled back without interruption with filtration process. Various samples of water with certain amounts of turbidity enter through a feed pipe and being distributed to the Filter. A central column runs from top to bottom of the Filter. The water is led through an outer tube in the column by a set of radial, distributor arms. The polluted water flows up ward through the Sand bed. The water emerges; clean, in the top section of the tank, and eventually spills over a weir, and then inters into a discharge pipe. In this research, the continuous Sand Filter was studied to determine its disinfection efficiency in addition to turbidity removal. The results showed that the Filtered water had a high quality and the turbidity reduction was 95.5 %. Inspecting the work of the Filter had revealed that the removal rates of coliforms and microbial colonies were 99.67 % and 98.99 % respectively. On the other hand, by the use of direct filtration, turbidity reduction was over 97 %. In direct filtration, drinking water with less than 1 NTU turbidity was provided. This continuous Sand Filter has the advantage of stable operation and more energy saving as compared to the conventional ones.

Background and purpose: Today, due to the reduction of water resources, separation of graywater from domestic wastewater and its reuse has gained more interest. The aim of this study was toapply multi-layer filtration (MLF) for removal of nutrients from gray water. Materials and methods: This laboratory-scale study was carried out in 2. 3-19. 2 gr. COD / L. dorganic loading rates (OLR) over a period of 157 days. In this study, synthetic gray water was used asinput to the multi-layer Filter. The MLF system included three layers: Sand, silica, and granular activatedcarbon. Furthermore, the scanning electron microscopy (SEM) images were used to determine the biofilmformation on the media surface. Results: The best removal efficiencies of COD, BOD5, TKN, and TP were 98. 87, 99. 84, 99. 5, and 98% achieved in OLR 19. 2, 12. 8, (13. 2, 4. 6) gCOD/l. d, SOR 5. 76, 2. 88, and 5. 77 m/hr, respectively. The study on the effect of loading rate revealed that by increase in OLR, the system efficiency to removeBOD5 and COD increased. Nevertheless, for TKN and TP, the efficiency decreased with increase in OLR. Also, according to SEM images, biofilm had grown well in the media, which can be effective in removingpollutants from gray water. Conclusion: Using multilayer filtration could be an appropriate option in removing nutrientsfrom gray water in different loadings.

The presence of particles such as algae, clay, organic materials and water-soluble substances often create turbidity or color in water. In recent years, electrocoagulation process has attracted an extensive attention due to its advantages. Since Sand Filters are widely used in water treatment industry and their corresponding backwash water is large in volume, turbidity removal will save water consumption and its recycling. In this study, real samples of backwash water from Sand Filters of a water treatment plant in Alborz province were collected. The turbidity removal was further evaluated under operating conditions of 6, 12, 18 and 30 V as the exerted voltages, electrode distances of 1 and 1. 5 cm, different initial turbidities (391 NTU as sample 1 and 175 NTU as sample 2), iron and steel as the sacrificial electrodes in a continuous electrocoagulation reactor. According to the results, the optimum conditions without considering the process economy was found to be 30 V, the iron electrode and electrode distance of 1 cm and samples 1 and 2 had an effective turbidity removal efficiency of 98. 4 and 91. 6%, respectively.

Backgrounds and Objectives: Improvement of water quality standards and inability of mono layer Filters in producing such quality caused researchers attended to multi-layer Filters.Due to specific characteristics of anthracite and leca can improve removal of organic materials and Surface over flow rate.The aim of this research was evaluation performance of dual media Filters (anthracite/leca) in removing of organic materials and turbidity from Ahvaz Water treatment plantMaterials and Methods: In this study two pilots built for investigation of mono layer Filter and dual media Filter performance. The researcher used Sand in structure’s media of mono layer Filter and composition of anthracite, Sand and leca in structure’s media of dual media Filter, respectively. In this study single and dual layer Filter pilot examined in term of organic matter and turbidity removal efficiency.  Results: Results indicated that removal of organic matter by single layer Filter (Sand), dual media Filter (anthracite, and Sand), dual media Filter (leca and Sand) was 7%, 12%, 4/2% respectively. And also Turbidity removal by single layer Filter (Sand), dual media Filter (anthracite and Sand), dual media Filter (leca and Sand) was also 69%, 80%, 74% respectively.Conclusion: Results of this study showed that upgrading of Single layer to dual layer with anthracite and leca media can‘t show a significant affect in TOC removal.

Introduction: By appropriate method can be recycled more than 95 percent effluent backwashing the Filter. This study aimed to examine the efficiency of the electrocoagulation process on turbidity and suspended solids removal from backwash effluent of rapid Sand Filter of water treatment plants No 1 in Karaj.Methods: This bench-scale experimental study was carried out on the samples of backwash effluent in a batch system. The Plexiglas tank with a volume of 4 liters, containing of 4 plate electrodes made of aluminum and iron was connected to a direct current power supply. Samples every 15 minutes to measure turbidity and suspended solids collected in the middle of the reactor and examined. Effect of several parameters such as current density, reaction time and voltage were studied. The total number of samples tested were 48. Turbidity and total suspended solids was measured by nephlometry and gravimetric method, respectively.Results: The highest removal efficiency of turbidity and suspended solids in reaction time of 60 minutes, current density of 2 mA and a voltage of 45 mV was observed. The highest removal efficiency of turbidity in aluminum and iron electrodes were 96.83 and 83.77 %, respectively. Also The highest removal efficiency of suspended solids were 96.73 and 86.22 %, respectively.Conclusion: The results showed that electro- coagulation process can be a good choice to remove turbidity and suspended from backwash of rapid Sand Filter. Aluminum electrode efficiency in the removal of turbidity and suspended solids was greater than the iron electrode.