During most of this century. the tr

During most of this century. the trend has been for more mechanized
wastewater treatment systems with almost every aspect of the various processes
under the direct control of the operator. In the last twenty years. however.
approaches that do not involve the same "concrete and steel" mentality have drawn
more attention. Sho-rtly after the enactment of the Clean Water Act (PL92-500) of
1972, alternate methods of wastewater treatment once again became recognized as
valid means of achieving the required level of effluent quality. Initially. attention
was centered on existing natural systems such as wetlands and coastal marshes, but
more recently, constructed systems using aquatic plants have been investigated.
In the early days of sanitary engineering, natural treatment was the only
method known. Initially, treatment was not even an objective, nor were the
processes understood. Wastewaters were simply disposed of in the nearest river,
lake. or swamp if one was available. As the communities grew. the carrying
capacity of the receiving water was eventually exceeded and problems began to
arise in terms of aesthetics, public health, environmental effects, or, more
commonly, a combination of the three. The need for treatment prior to discharge
was recognized at this point. and primary treatment was developed to remove most
of the larger solids and organic matter. Natural systems were more or less
forgotten because they had not performed well under the required loads.

ผลลัพธ์ (ไทย) 2:

During most of this century. The Trend has been for more mechanized.
Wastewater Treatment Systems with Almost Every Aspect of The Various processes.
The operator under The Direct Control of. In the last twenty years. however.
approaches that do involve Not The Same "Concrete and Steel" mentality Have drawn.
more Attention. Sho-Rtly After The enactment of The Clean Water Act (PL92-500) of.
1 972, alternate methods of Wastewater Treatment once Again Became As recognized.
valid means of achieving effluent The Required Level of Quality. Initially. Attention
was centered on existing natural Systems Such As Wetlands and Coastal marshes, but.
more recently, constructed using Systems Aquatic Plants Have been Investigated.
In The Early days of Sanitary Engineering, Treatment was The only natural.
Method Known. Initially, Treatment Not Even an Objective was, nor were The.
Understood processes. Simply Wastewaters were disposed of in The Nearest River,.
Lake. or swamp if one was available. As the communities grew. The carrying
Capacity of Water The receiving was eventually exceeded and problems began to.
arise in terms of Aesthetics, public Health, Environmental effects, or, more.
commonly, a Combination of The Three. The Need for Treatment Prior to discharge.
was recognized at this Point. and Primary Treatment was developed to Remove Most.
of The larger solids and Organic Matter. Systems were more or less natural
Forgotten Not Because they had performed Well under The Required Loads.