洗滤池根据采用的滤料不同的冲洗强度及冲洗时间分为:①q=12~15L/(s·m2),t=7~5min;
②q=13~16L/(s·m2),t=8~6min;
③q=16~17L/(s·m2),t=7~5min;
如果采用双层滤料过滤其冲洗强度和冲洗时间应选( )。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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