But the conventional activated sludge process technology has some shortcomings: long water residence time, low processing power per unit area, large area reactor, sludge bulking and so on.

但是传统的活性污泥法工艺存在工艺流程长、污水停留时间长、单位面积处理能力低、反应池占地面积大、污泥膨胀等缺点。

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The reasons accountable for the decline of the fish resources are due to the low reproduction capacity and the long development time of the fish, overfishing and water pollution.

造成胭脂鱼资源下降的原因主要与其自身繁殖力低，发育时间长，以及过度捕捞和水域污染等因素有关。

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Microcystis-bloom in Fenghuangshan reservoir occurred in Feb. -2009, long water retention time, low precipitation and inflow, high temperature were the main reasons.

凤凰山水库2009年2月初发生局部微囊藻水华，主要原因是较好的水体稳定性（高水位，较长的水力滞留时间，较低的入库流量和降雨量），以及水温的迅速回升。

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High demand for water amid the heat wave and problems with soil shrinking as the ground warms has resulted in burst pipes and low water pressure in Oklahoma City, prompting officials to issue mandatory water-use restrictions for the first time in at least a decade, according to utilities department spokeswoman Debbie Ragan.

CNN: Heat advisories issued to states dwindles to 15

They will be closed only for short periods of time and only during the winter when the water temperature and light are too low for algal blooms.

ECONOMIST: Flood barriers