Characteristics and Phototoxic Effects of Sewage Sludge for Agricultural Uses

Abstract

The objective of this study was to assess the suitability of utilizing sewage sludge in agriculture. Sewage sludge samples, namely non digested sludge, digested sludge and composted sludge were taken from the wastewater treatment plant at “Nongkham”. Chemical characteristic analysis and seed germination testing were carried out. Chemical characteristics analyzed were pH, electrical conductivity, moisture content, organic matter, organic carbon, C/N ratio, macronutrient and heavy metals. In seed germination, Pak-choi (Brassica camprestris L. var. parachinensis Bailey) and Chinese cabbage ( Brassica rapa L. subsp. pekinensis var. cylindrical ) seeds were tested in the 3 extracted sewage sludges and distilled water for control. The results showed that some parameters such as K was below the standards of organic fertilizer and concentrations of Cu and Ni were above the maximum permitted of sewage sludge for agriculture. For seed germination test with Pak-choi and Chinese cabbage seeds in composted sludge extract, no significant differences were observed in seed germination and in mean root length when compared with control (distilled water). Composted sludge might be used as soil conditioner, if the amount of composted sludge used can be controlled or the problem of high concentrations of Cr and Cu can be solved. Immobilization of Cr and Cu to reduce environmental contamination is recommended for further study.