There is also a need for research aimed at understanding the effects of repeated land application of effluent on soil quality and crop yields, as spreading is a common disposal practice.
The more organic matter in effluent irrigated soil might be due to the high organic nature of the effluent.
The contamination factor (Cf) for heavy metals accumulated in sugar mill effluent irrigated soil and P. glaucum was calculated following Håkanson (1980).
These contrasting effects of the fermented effluent on soil fertility and plant growth suggest that fermentation period of 20 days may be adequate for the effluent to express its fertilizer value in soil but this may not detoxify it of phytotoxic compounds to an agronomically safe level, hence contradicting its potential as biofertilizers.
There have been studies pointing to the beneficial of effects of application of such other vegetable oil effluents as olive and palm oil-mill effluents on soil fertility indices and agronomic productivity (Macci et al. 2010; Nwoko and Ogunyemi 2010), but we are not aware of any corresponding evidence for cottonseed oil-mill effluent (COME).
The direct discharge of effluent in soils can be used as a primary or secondary treatment and offers opportunities for groundwater recharge and wastewater storage.
Achak et al. (2009) reported that the OMW acidity was due to the presence of phenolic and fatty acids, subsequently the application of this effluent to soils could accumulate salts and phytotoxic compounds, change pH and leach nutrients that could contaminate the ground water source.
In eastern Botswana, buildup of nitrogenous latrine effluent in soils and subsequent downward leaching of nitrate appeared to promote dissolved nitrate concentrations > 500 mg/L in groundwater (Lewis et al. 1980); the authors concluded that the fissured bedrock aquifer allowed for rapid contaminant transport.
The effect of effluent discharge on soil depends on soil properties: for example, silty clay holds water longer than sandy soil, while water is consumed more rapidly by sandy soil (Calkins 2011).
Free, infective phages for B. anthracis are also found in many environments, including sewage, tannery effluent, animal hair, soil and water at or near anthrax carcasses, as well as soil at non-endemic areas [18], [47], [48], [49], [50], [51], [52].
