Summarizing Solidliquid Separations Technology

as a resource that can be recycled or reused. That concept embodies the spirit of pollution prevention.

Suspension

Ultimate Solids ,

A - Addition of Additives

Suspension

Clean Walcr

Clean Walcr

As already noted, all the sludge produced at a treatment plant (whether it be sewage or industrial in origin) must be disposed of ultimately. Treatment processes such as have been described may reduce its volume or so change its character as to facilitate its disposal, but still leave a residue which in most cases must be removed from the plant site. Like the liquid effluent from the treatment plant, there are two broad methods for the disposal of sludge :

disposal in water, and disposal on land.

Ultimate Solids ,

This applies regardless of whether or not the sludge is treated to facilitate or permit the selected method of disposal. Before

A - Addition of Additives discussing the specific options in detail, let's first take a look at the big picture for each option.

Disposal in water is one option to consider. This is an economical but not common method because it is contingent on the availability of bodies of water adequate to permit it. At some seacoast cities, sludge either raw or digested is pumped to barges and carried to sea (the context of these discussions is strictly sewage) to be dumped in deep water far enough off shore to provide huge dilution factors and prevent any ill effects along shore. In the past few years there has been an increased problem of pollutional loads, well above safe standards, affecting the south-shore beaches on Long Island, facilitating the closing of the beaches to the public. Some of these pollutional loads have been attributed to sludge deposits coming to shore form offshore sludge barging operations. Where barged to sea, the value of some treatment such as thickening or digestion, depends on the relative cost of the treatment and savings in cost by barging smaller volumes, or the value of gas produced by digestion. Overall, this is an environmentally unfriendly option, and the bottom line is that it is no different that straight landfill, and in fact can be more environmentally damaging. It is plain and simple, an end-of-pipe solution with trad-offs.

Under land disposal the following methods may be included:

Project Earth Conservation

Project Earth Conservation

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