排放时间 meaning in Chinese

drain time

Further , economic analysis showed that using the darkened sand could reduce operation cost . however , it is suggested that strict inspecting of water quality should be applied for the blacked sand , and preliminary filtrating time should be prolonged in order to ensure water quality
这表明黑化砂与清洗再生砂对过滤的出水水质无明显的不良影响，可以在生产中使用，但对黑化砂必须严格监控水质，适当延长初滤水的排放时间，以保证出水水质。