Toxicity assessment of common xenobiotic compounds on municipal activated sludge: comparison between respirometry and Microtox®

Assessment of toxicity and biodegradability on activated sludge of priority and emerging pollutants

“…The EC50 value reported by Ricco et al [3] for dichloromethane (2590 mg/L) was somewhat higher than that obtained in this study.…”

“…The reaction vessels, placed in a thermostatized orbital shaker, were stoppered so that oxygen transfer from air to the liquid can be neglected. [6] The toxicity was evaluated using the method proposed by Ricco et al [3], based on the respiration inhibition test [14] for activated sludge. The procedure consisted in shortterm (30 min) respirometric measurements using unacclimated sludge (350 mg/L) with an easily biodegrable substrate (sodium acetate) alone, as reference, and with different concentrations of the target compound.…”

“…However, the microbial activity may be affected by the presence of xenobiotic compounds such as chlorinated compounds, polyaromatic hydrocarbons, dies, pesticides and pharmaceuticals. [2][3][4] Thus, before performing a biological treatment it is necessary to assess the toxicity and biodegradability of the wastewater on the activated sludge. [5,6] It is important to recognize that toxicity and biodegradability are not always mutually exclusive.…”

“…[12] Respirometric measurements are commonly used to determine the effects of toxicants on the activated sludge. [3,[13][14][15][16] Although the respiration rate can be quantified by different methods, the oxygen uptake inhibition rate [14,17] is most frequently used to evaluate the toxicity. [2,6,13] A test using activated sludge for toxicity assessment will not indicate total toxicity since the bacterial density and diversity is high and only the inhibition of the most abundant organisms which are growing faster under the tests conditions is indicated.…”

Utilisation of respirometry to assess organic matter reduction of effluents from the Camaçari industrial complex (BA, Brazil)

“…In a study with Microtox at this WTP during the same period, Araújo et al (2005) found a mean toxicity reduction of 92.71%. Several authors have shown that Microtox test is more sensitive to the action of toxicants than respirometry (Kilroy and Gray, 1992;Dalzell et al, 2002;Ricco et al, 2004). On the other hand, respirometry seems to be more accurate than Microtox to assess the toxicity reduction at this WTP, since it is a more direct method for assessing sludge activity and thus toxicity to sludge (Ren, 2004) and the whole microbial community is involved in the process, instead of only one organism (Vibrio fischeri), in the Microtox test.…”