13 Some engineers suggest that this period be extended to allow a sand bed to rest for a month after the sludge cake has been removed.
13 Some engineers suggest that this period be extended to allow a sand bed to rest for a month after the sludge cake has been removed.
一些工程师建议这段时间应该被延长，以便沙床能够在泥浆块被移除后休息一个月的时间。