Intermittent Sand Filtration Research Articles

Residual heavy metal removal by an algae-intermittent sand filtration system

A laboratory scale study was undertaken to determine the feasibility of using algae growing in wastewater lagoons to absorb residual heavy metals for subsequent complete removal by intermittent sand filtration of the metal laden algae. In semi-continuous cultures the mixed algal flora native to wastewater lagoons absorbed 70–90% of the cadmium and copper from the wastewater media. Chromium absorption was less by ratio (20% was absorbed), but the mass of chromium removed was much greater as high levels of chromium were added. Only one alga (Oscillatoria sp.) which was extremely resistant to chromium grew in the chromium exposed cultures. Nearly total removal of the cadmium and copper was achieved by the algae-intermittent sand filter system. The net chromium removal agreed with the accumulation analyses. The technical feasibility of removing certain heavy metals from wastewater with such a system was established. However, in depth laboratory and field studies must be conducted to maximize system efficiency, demonstrate tactical limitations, and establish design specifications.

Intermittent Sand Filtration of Household Wastewater

Intermittent sand filtration of septic tank and aerobic unit effluents are investigated as a feasible on-site wastewater treatment and disposal system. Sand filters receiving septic tank and aerobic unit effluents were constructed and monitored at two home sites in Wisconsin. The filters were constructed to allow access to the sand surface for periodic maintenance. High hydraulic loadings rates of 2 gpd/sq ft to 20 gpd/sq ft were used. data, date, including effluent qualities, methods of rejuvenation, and costs of the sand filters, are presented.

Oxygen Relationships in Intermittent Sand Filtration

A model for processes in intermittent sand filtration is described and an expression for oxygen transfer is formulated. The model assumes that aerobic bacterial activity within the sand or soil matrix is limited by oxygen deficiency while the surface is ponded. Atmospheric oxygen reenters into the soil after infiltration ends. Aerobic activity is resumed, but oxygen penetration is limited and some depths may be always anaerobic. This condition leads to large variations in the concentration of certain contaminants in the percolate. Analyses of soil moisture in field studies and of effluent from laboratory sand columns substantiated the model. The oxygen content at sufficiently long times after addition of wastes can be described by a quasi steady-state diffusion equation including a term for an oxygen sink. Measurements of oxygen content during laboratory and field studies show that the oxygen profile changes only slightly up to two days after the quasi-steady state is attained. Results can be applied in operating existing facilities and in interpreting data from pilot-plant studies.