Abstract
Discharge of toxic industrial wastewaters into biological wastewater treatment plants may result in inhibition of activated sludge bacteria (ASB). In order to find an appropriate method of detoxification, the wastewater of a pesticide-processing plant in Vietnam was treated with three different methods (FeIII, powdered activated carbon (PAC), Fenton (FeII/H2O2)) analyzing the detoxification effect with the nitrification inhibition test (NIT), respiration inhibition test (RIT) and luminescent bacteria test (LBT). The heterotrophic ASB were much more resistant to the wastewater than the autotrophic nitrificants. The NIT turned out to be more suitable than the RIT since the NIT was less time-consuming and more reliable. In addition, the marine Aliivibrio fischeri were more sensitive than the nitrificants indicating that a lack of inhibition in the very practical and time-efficient LBT correlates with a lack of nitrification inhibition. With 95%, the Fenton method showed the highest efficiency regarding the chemical oxygen demand (COD) removal. Although similar COD removal (60–65%) was found for both the FeIII and the PAC method, the inhibitory effect of the wastewater was reduced much more strongly with PAC. Both the NIT and the LBT showed that the PAC and Fenton methods led to a similar reduction in the inhibitory effect.
Highlights
IntroductionThe wide variety of industries and their complex production methods result in various types of wastewater containing toxic environmental chemicals such as plant protection agents (PPA), heavy metals, pharmaceuticals, etc
This process is based on the fact that at a pH of 1.9 nitrite ions form a pink dye with 4-aminobenzosulfonamide, orthophosphoric acid and N-(1-naphthyl)-1,2-ethylenediamine dihydrochloride, which can be photometrically detected at a wavelength of 540 nm
It is expected that the sample with the highest concentrations of chemical oxygen demand (COD), N and P will have the highest concentrations of pesticides
Summary
The wide variety of industries and their complex production methods result in various types of wastewater containing toxic environmental chemicals such as plant protection agents (PPA), heavy metals, pharmaceuticals, etc. Toxic environmental chemicals are often persistent compounds with a high bioaccumulation potential [1,2]. Chemical agents impair several vital metabolic processes of various organisms [3]. PPA, for example, contain highly bioactive compounds that are used against certain organisms, i.e., pests or competitors. From the place of their application, PPA reach the surrounding environment in a wide variety of ways, in particular, soil, water and air [2]. PPA can be classified according to their mode of action, substance class and application. Insecticides (mainly halogenated hydrocarbons, pyrethroids, phosphoric acid esters and carbamates), herbicides (mainly phenoxycarboxylic acids, heterocyclic compounds, phosphonates) and fungicides (often organometallic compounds) are of the greatest importance worldwide [4]
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