Influence of Cadmium on the Performance of an Activated SBR Sludge Treatment

Abstract

High concentration of heavy metals is a toxic factor for most microorganisms. As a result, such metals give rise to severe disruption in wastewater treatment operations. It has been noticed, however, that biological systems may adapt to heavy metals when their concentration is limited. In fact, such systems can even produce some degree of metal elimination provided that an optimal exposure tempo is guaranteed. On the other hand, irreversible damage may occur when metal concentration is sufficiently high. It is the aim of the present study to report on the inhibiting effects due to Cadmium on the activated sludge treatment method. To that end, different Cd concentrations were tested (ranging from 0.25 to 14 mg l(-1)) in a Sequential Biological Reactor, using synthetic wastewater without recirculation. The feed water providing 325 mg l(-1) COD and 30 mg l(-1) NH4+ -N. The process was screened by checking elimination percentages for COD and ammonia, as well as the evolution of ciliate protozoa. In addition, research was carried out on Cd assimilation by the activated sludge system by means of measuring in the mixed liquor and in the effluent. Results showed a marked decrease in purification efficiency when Cd-concentration rose over 14 mg l(-1), in which case COD elimination dropped from 98% to 41% while ammonia elimination went down from 98% to 32%. The Sludge Biotic Index decreases to 0 at Cd concentrations above 10 mg l(-1).

The effects of continuous Cu(II) exposure compared with a shock dosage of Cu(II) on pollutant removal in activated sludge

“…This experiment allowed us to investigate the effect of continuous Cu(II) exposure on the ability of AS to remove pollutants. The removal efficiency of COD and NH 3 -N from wastewater is usually used to indicate the changes in the biological activity of AS in the presence of heavy metals [8,[16][17][18]. Therefore, by determining the concentrations of COD and NH 3 -N over a long period, we were able to compare the continuous toxicity of Cu(II) on AS in both the CR and ER.…”

Interaction between Heavy Metals and Aerobic Granules

“…Many researchers studied the effects of heavy metals on activated sludge system (Ong et al, 2004;Ong et al, 2005b;Santos et al, 2005;Sirianuntapiboon & Ungkaprasatch, 2007;Tsai et al, 2006). However, results from these studies are difficult to be compared due to the various metal bioavailability caused by different operation modes, substrate compositions, seed sludge sources and concentrations.…”