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|Title:||Wastewater renovation by a prototype slow infiltration land treatment system|
|Authors:||Iskandar, I. K. (Iskandar Karam), 1938-|
Sletten, Robert S.
Leggett, Daniel C.
Jenkins, Thomas F.
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 76-19.|
Abstract: The feasibility of a slow-infiltration land treatment system as an alternative to advanced waste treatment of wastewater was studied using six outdoor test cells. Wastewater was applied to forage grasses by spray irrigation. Parameters studied were wastewater application rate, effect of pretreatment and soil type and seasonal effects on the treatment system. Activated sludge pretreatment of the applied wastewater did not improve the overall quality of the product water from this slow-infiltration system. The uptake of nutrients by forage grasses accounted for significant removal of nitrogen and phosphorus from applied wastewater during the growing season. Other renovative mechanisms, namely nitrification/denitrification of applied nitrogen and phosphorus immobilization and fixation by the soils may have accounted for further renovation of the applied effluents. The nitrogen loading rate appeared to be the critical factor in limiting the amount of wastewater that could be successfully applied to this type of land treatment system, at least over the short term. Also the renovative mechanisms for nitrogen were found to be seasonally dependent. Due to decreased nitrification and sorption of ammonium by soil components nitrogen was stored in the winter months. The sorbed ammonium underwent nitrification in the warmer months, giving rise to a high concentration of nitrate-N in spring. The higher nitrate concentrations observed in leachate after the first year of wastewater application were attributed to mineralization of native organic-N. Application of 15 cm/week of secondary effluent containing 27 mg/l total N to sandy loam soil produced percolate water containing N03-N concentrations consistently in excess of accepted drinking water standards (10 mg N03-N/l). Leaching of phosphorus was not observed but needs further study to predict long-term effects. Winter-time application was successful in terms of operational parameters, but the renovative capacity for nitrogen was impaired. The effect on other water quality parameters such as suspended solids, BOD, fecal coliform and organic-C was essentially complete removal. There was a negative chloride balance which was presumed to be due to plant uptake.
|Appears in Collections:||CRREL Report|