Conversion of Biological Treatment Plant Sludge to Organic Fertilizer for Applications in Organic Farming

Abstract

Conversion of the sludge generated in the biological treatment plants of glove dipping industries of Sri Lanka to a valuable organic fertilizer after removing toxic metal ions such as heavy metals and excess Zn and Al present in the sludge to allowable limits is described. In order to do so, the raw materials used were analysed for these species and for their nutritional values. Removal of metal ions by different acids such as HNO3 and acetic acid digestion processes are revealed and the results are compared. Dilution of the metal ion-removed sludge with other raw materials used in organic fertilizer production to enable maintain right C:N ratio and the use of these materials in the fertilizer production process used are presented. Application of the fertilizer to soils of fruit and vegetable plantations and measurement of Zn, Al and heavy metals in the soil and plant parts and their crops as a function of time is also described. The quality of vegetables and fruits produced by applying this new fertilizer is compared with those obtained in the open market.It has been shown that the former contains no or much less than maximum allowable limits of heavy metals or toxic species when compared to those grown using other organic fertilizers. This study is useful for industrial biological treatment plant sludge management by converting it to a useful product.

Nutrient removal in sludge extracts and protein production by cultivation of Candida utilis

“…Therefore, amino acids content in the yeast is an ideal protein source of organic fertilizer because it possesses high content of essential amino acids and fully meeting the nutritional standard. Previously, the proteins recovered from ES without strain addition could be considered as organic fertilizer 48 . However, proteins in this study need more tests to prove that they can meet the safety standards before they can be used in more fields.…”

“…Previously, the proteins recovered from ES without strain addition could be considered as organic fertilizer. 48 However, proteins in this study need more tests to prove that they can meet the safety standards before they can be used in more fields. It has been reported that toxic metals, organic pollutants, and microbial toxins are concentrated in sewage sludge through the primary and secondary treatment processes.…”

“…Finally, through membrane filtration, the medium for C. utilis cultivation is relatively safe. 48,49 Organic matters were almost consumed in ESH according to analysis of 3D-EEM EEMs can reveal the classification and content information of organic pollutants when it is used in water quality measurements. In order to further quantify and characterize the organic components in ESH and changes of the water phase, as well as avoid the by-product brought by C. utilis, the investigation of fluorescence EEMs was analyzed.…”

“…Ultrasound could destroy the cell structure of microorganisms and kill the harmful microorganisms in the hydrolyzate. Finally, through membrane filtration, the medium for C. utilis cultivation is relatively safe 48, 49 …”