Some Chemical and Biological Additives With Hyperaccumulator Plants for Amendment the Sandy Soil Contaminated for Long Term by Sewage Water

3 Abstract: Long- term irrigation with sewage water in the sandy soils cause severe adverse contamination consequences with potentially toxic elements (PTEs), potential organic pollutants (POPs) and/or enteric pathogens that lead to degradation of these lands. Cairo is now served by six large wastewater treatment works, which produce significant quantities of sewage water. The preferred option is to use this in agriculture, particularly in reclaimed desert land, which is inherently deficient in organic matter, nutrients and trace elements. However, there are concerns about the long-term accumulation and potential effects of heavy metals and pathogenic organisms. Abou Rawash Farm is reclaimed desert land west of Cairo. For combating this type of contamination a field experiment was conducted at Abu-Rawash sewage farm where the soil has been irrigated with water sewage for 32 years and there are concerns about the contamination of the site by potentially toxic heavy metals (The contamination index of PTEs was 633.9) and enteric pathogens. The site provides a possible model of the potential long-term effects of heavy metals and other pollutants on crops in the soils irrigated with sewage water in Egypt. This work is a part of the bioremediation project funded by Egyptian Academy of Scientific Research and Technology (Science and Technology Development Fund, STDF) and implemented by NRC. During the previous tasks implemented throughout the project for the bioremediation of sewage soils, some treatments gave pronounced effectiveness and hence it was tried in this field experiment to innovate a proper bioremediation protocol for sewage soils using successive chemical, microbial and phytoremediation treatments. The hyperaccumulator plant used for decontamination of these pollutants was Indian mustard (Brassica juncea Czern). Six treatments including fallow soil (irrigated without growing crop plants), cultivated control, inoculated with arbusculer mycorrhiza (AM), soil inoculation with Thiobacillus (a mixture of Thiobacillus ferrooxidant and Thiobacillus thiooxidant), soil treated with a mixture of 250 gm bentonite plus 250 g rock phosphate and inoculated with PDB and soil treatment with all the biological and chemical treatments. The contaminated soil was chemically or biologically treated two months prior sowing the Indian mustard crop. Soil quality criterion index (Zn equivalent model) was numerically expressed for the levels of PTEs toxicity. Plant samples from each treatment were taken at vegetative and seed maturity stages and the growth criteria as well as yield and yield attributes were determined. The PTEs, POPs and enteric pathogens were determined at three sampling occasions. Plant analysis and PTEs accumulation as well as the level of dehydrogenase in soil rhizosphere were determined. Statistical analysis was applied using SAS software. The results indicated that soil inoculation with AM and the integrated treatments to the cultivated land with Indian mustard plants seems to be more effective in achieving the phytoremediation process. Safety seed yield of Indian mustard plants were significantly increased by 16.6% when bentonite was used while with the application of Thiobacillus, the integrated and AM treatments caused a reduction in the safety seed yield by 18.8, 6.6 and 0.4%, respectively. However, the plant weight was increased in most cases. A cumulative effect was recorded when the three tested remediative amendments were applied together, where the aerial parts and total plant weight were increased by 81.4 and 81.6%, respectively in comparison to the plants grown without