ACID CHARACTERISTICS OF DISSOLVED ORGANIC-MATTER IN WASTE-WATER

The presence of dissolved organic matter (DOM) in a wastewater treatme nt system can significantly affect the uptake of heavy metals by sludg e particulates. The characteristics of DOM, its concentration, and the solution pH are important parameters governing the heavy metals uptak e reaction. The characteristics of DOM of various wastewater and sludg e (primary, secondary, and tertiary) samples collected from four munic ipal wastewater treatment plants were investigated. Results showed tha t the dissolution of DOM from sludge is significantly affected by pH a nd suspended solids concentration. Results also showed that DOM contai ns two discrete acid groups that are available for metals complexation . The site concentration and acidity constants were determined by an a lkalimetric titration method. For all DOM samples studied, the acidity constants, pK(aA) and pK(aB), were 5.3 and 9.5, respectively. Based o n the acidity constants and the Fourier transform infrared spectra, it is believed that the acid sites consist of carboxylic and amino funct ional groups. The density of the first acid site was approximately 10( -5) mol/mg chemical oxygen demand for all samples studied. However, th e density of the second acid site varied significantly among the DOM s amples investigated.