Uncouplers and activated sludge—the impact on synthesis and respiration

Abstract

Halogenated organics are among the most commonly-encountered anthropogenic compounds accumulating in the environment. These compounds have many behavioral characteristics in common. Many are carcinogenic; many are toxic; almost all resist biodegradation; all undergo bioconcentration and concentration in sediments. One group of halogenated materials, the halogenated phenols, interact with microbial cell tissue and higher-life forms in a way not seen with the other compounds in this broad category. That is, they will uncouple oxidative phosphorylation, the energy transfer process which permits the accumulation of the energy of substrate oxidation as adenosine triphosphate which is subsequently used in synthesis. The present study reports on laboratory work which serves to quantify the various results of energy uncoupling. These are an increase in oxygen use, a decrease in synthesis and a decrease in the rate of normal substrate uptake. The work is carried out utilizing four common types of organics as growth substrates. The consequence of the phenomenon of uncoupling in full-scale treatment plants, based on experiences at one of the Phoenix wastewater treatment plants, is discussed.

Sludge minimisation technologies

“…Many researchers have investigated the development of uncoupler-containing activated sludge process for minimisation of excess sludge production (Okey and Stensel 1993;Low and Chase 1998;Mayhew and Stephenson 1998;Low et al 2000;Chen et al 2000). About 50% biomass reduction was achieved at a PCP concentration of 30 mg/l compared with no uncoupler (Okey and Stensel 1993).…”

Minimization of excess sludge production for biological wastewater treatment

“…Oxidative phosphorylation can be effectively uncoupled by the addition of organic protonophores, which carry protons through cells' intracellular cytoplasm membrane thus dissipating the driving force. Recently, many researchers focused on sludge reduction induced by chemical uncouplers, such as 2,4-dinitrophenol (dNP), para-nitrophenol (pNP), pentachlorophenol (PCP) and 3,3 0 ,4 0 ,5-tetrachlorosalicylanilide (TCS) [58][59][60][61][62][63][64][65][66]. One of the first oxidative uncouplers to be studied was 2,4-dinitrophenol (dNP) in 1948 by Loomis and Lipmann [58].…”

“…Recently, many researchers focused on sludge reduction induced by chemical uncouplers, such as 2,4-dinitrophenol (dNP), para-nitrophenol (pNP), pentachlorophenol (PCP) and 3,3 0 ,4 0 ,5-tetrachlorosalicylanilide (TCS) [58][59][60][61][62][63][64][65][66]. One of the first oxidative uncouplers to be studied was 2,4-dinitrophenol (dNP) in 1948 by Loomis and Lipmann [58]. Table 2 lists effect of some chemical uncouplers on reducing sludge production, and the dose of TCS required for achieving similar sludge reduction is the least compared with other four chemical uncouplers (pNP, dNP, TCP, mCP).…”

“…Several chlorinated and nitrated phenols and benzoates were tested for their short-term effects on cell yield, COD consumption, and respiration of activated sludge [58]. About 50% biomass reduction was achieved at a 2,4-dichlorophenol (DCP) concentration of 30 mg/l compared with no uncoupler.…”

Metabolic Uncoupling: Biomass Control Strategy in Microbial Processes

“…Full scale application of uncouplers has been reported at a wastewater treatment plant located in Phoenix, Arizona. Halogenated phenols were observed to cause reduced biomass yield, modest reduction in substrate uptake and increased oxygen consumption [10].…”