The Myth of Even Effluent Distribution in Sand

by Curt Kerns, M.S., R.P.Bio., C.F.S.

Sand, having the physical characteristic of large pore sizes, only moves water anisotropically, that is symmetrically in one direction, which in the case of coarse sand is downwards.  As a consequence it is an inferior medium to attempt to evenly disperse wastewater in, and consequently is much overused in onsite wastewater management.  Organic enrichment is a far, far more dependable mechanism to move water isotropically, that is in all directions, thus better insuring a more even hydraulic distribution.   

I see no theoretical support for the contention that in sand, even dispersal of secondarily treated effluent can be assumed to be the result of conventional positive pressure distribution.  Sand may have one advantage, however:  in the pictured field within a few months of a specific orifice plugging, a lack of commensurate vegetation growth will probably be evidenced on the surface.

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Even distribution in sand? Above, A lightly loaded secondary treatment plant system discharges to a sandmound
 

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“The significant problems we face cannot be solved at the same level of thinking we were at when we created them.” Albert Einstein

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