Synergistic-type response

Although these surfactants represent less than 1% of the U.S. production of surfactants, the market use is increasing dramatically because of their unique properties [353]. Of particular importance is the synergistic effect that amphoteric surfactants have when used in conjunction with other types of surfactants. The non-eye-stinging characteristic of these compounds has been responsible for the upsurge in the baby shampoo market over time [354,355]. 

If the response of the organism is produced by a combination of the two compounds, then they are said to exert joint action. This joint action can be further classified into simply additive, more than additive (i.e., synergistic), and less than additive (i.e., antagonistic). When this scheme is applied to multicomponent mixtures present in leachates of solid wastes, the analysis becomes more complex because the joint actions of different compound pairs may fall into different types of joint action. In the next section, three different modeling schemes are presented. 

The response of bacteria to the photocatalytic inactivation results from a combination of antagonistic and synergistic effects of different water components. Then, the response of bacteria generated by an individual substance could be very different from that observed if the same substance is accompanied by other chemicals. Photolytic treatment was also affected by chemical composition of water. The significant difference observed between both treatments indicates the specific action mode of each system (Rincon and Pulgarin 2007b). However, the extent of this observed difference depends on the type of water. Thus, for practical applications each type of water has to be considered as a specific case. 

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