STATISTICAL PROCESS CONTROL IN THE ASSESSMENT OF DRIP IRRIGATION USING WASTEWATER

ABSTRACT The aim of this study was to evaluate drip irrigation as a process, by monitoring the average flow applied by the emitter using tools of statistical quality control. Four kinds of drippers were selected, two inline labyrinth type and two online where one of the inline emitters was not self-compensating and the other, self-compensating emitter. The system was installed in the field and tested for 85 hours, using three kinds of treated domestic sewage effluents and tap water. The system was under statistical control when the emitters were new, however none of the drippers reaches the manufacturer's specification for average flow. The online drippers showed more dispersion for individual flow measurements and the non-self-compensating inline dripper was more accurately for this variable. After the end of experiment, irrigation process was not under statistical control for any kind of emitter. When using treated wastewater effluents for irrigation we recommend a first evaluation before 7 working hours, to implement appropriated correcting procedures to reduce clogging and as a result, maintain the process quality.

摘要 本研究旨在以统计质量控制（statistical quality control）工具监测滴头（emitter）的平均出流量，以此对滴灌（drip irrigation）工艺开展评价。本研究选取4类滴头（dripper），其中2款为内置迷宫式（inline labyrinth type）滴头，另外2款为外置式（online）滴头；内置式滴头中1款为非自补偿式，另1款为自补偿式（self-compensating）滴头。试验将该系统布设至田间，开展85小时的测试，测试用水涵盖3种经处理的生活污水（treated domestic sewage effluents）与自来水。当滴头为全新状态时，系统处于统计受控状态，但所有滴头的平均出流量均未达到厂商标称的规格参数。外置式滴头的单滴头流量测量值离散程度更高，而非自补偿式内置滴头的流量变量测量精度更优。试验结束后，无论使用何种类型的滴头，灌溉工艺均不再处于统计受控状态。若使用经处理的污水开展灌溉，建议在运行7个工作小时前开展首次评估，以实施适配的校正流程，减少堵塞（clogging）问题，进而维持灌溉工艺的质量稳定性。