Performance Of Filtration And Flushing Of Quartz Sand Media For Micro-irrigation

Micro-irrigation is the most efficient water-saving irrigation technology,which has broad application prospect. But the flow path in Micro-irrigation emitter is so small that plug happened easily,so filtering system is needed to add to the header of irrigation system. Graval media filter is one of the most common in production and predecessors have already conducted extensive research on it, nevertheless there is few on filter media performance and filter media options. Based on the former extensive research,this paper has studied on following aspects:1.In order to establish the filter criteria and select the minimum particle size which could cause blockage, the research on size and distribution of the impurity particles deposited in the drip irrigation tape has been done. 2.An orthogonal experiment regarding five levels respectively of four factors, namely,different size of mean filter,filtration rate,filter layer thickness,impurity concentration has been done in order to study the influence of these factors to the turbidity,the effective maximum diameter(D98)of the impurity particles in the filtered water and to the head loss of filtering layers. 3.An experimental research on the backwash of the filter model been cloged was carried out to analyze the influence of five filter layer height,five particle sizes of filter media and five backwash speeds to the effluent turbidity varying with time in backwash,graval media filter bed expansion height and the excretion order of the impurity particles varying with time.The conclusions are as follows :1. The maximum size particles were found in the central of the whole tape; the drip-irrigation system will be blocked obviously if the effective maximum diameter(D98)of the impurity particles flowing into the drip-irrigation system larger than 100μm,thus, the filter standard were drown up——it can meet the drip-irrigation water quality when the filtering precision is 100μm. 2. Among the four factors,the size of filter and the filter layer thickness played a decisive role to the filter effects; In this paper,the head loss equation of the filter bed was built based on the analysis of reasons causing head loss;the Variation laws of the effective diameter(D98)of the impurity particles in the filtered water was summarized along with filter layer thickness and the size of filter media, moreover, the trend graph was given. It provides theoretical basis for choose the filter. 3.Four to five minutes after the backwash began,the effluent turbidity would be steady and near to the clean water turbidity,the graval media filter bed expansion height was proportional to the backwash speed and the backwash time could not be saved effectively only through increasing speed,that mean the separation of impurity from filter material was complexity not only caused by the effect of flow shear action. After five or six minutes,the impurity particles of the drainage water would be stable and was very little.So we can know from them that the backwash time could be control,Generally five to six minutes was good.The above provides a theoretical basis for filter media selection, filter rate ,backwash intensity and time control indicators etc.for the micro-irrigation equipment.Thus ,it can achieve a better filtering effect, which ensures that the micro-irrigation systems to work with stable running...