Removal and Effects of Surfactants in Activated Sludge System (original) (raw)
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Evolution of acute toxicity of non-ionic surfactants over the biodegradation process
Environmental Toxicology II, 2008
The present work examines the toxicity of two non-ionic surfactants widely used in current detergent formulations: a fatty-alcohol ethoxylate, Findet 1214N/23 (R(-O-CH 2-CH 2) n-OH: 70% C 12 and 30% C 14 ; 11 average ethylene oxide units) and nonylphenol polyethoxylate with 9.5 average ethylene oxide units. The biodegradation tests were made according to the OECD 301 E test for ready biodegradability. These tests were made at different starting concentrations: 15, 20, 25, and 50 mg/L for Findet 1214N/23, and 5, 25, and 50 mg/L for nonylphenol polyethoxylate. Toxicity was assessed with the LumiStox ® 300 system, consisting of an instrument for measuring bioluminescence and an incubation unit according to the UNE-EN ISO 11348-2 guideline. This method is based on the luminous intensity of marine bacteria of the strain Vibrio fisheri NRRL-B-11177 after a certain exposure time to a toxic substance. The toxicity value was calculated as EC 50 , which is the surfactant concentration that inhibits 50% after 15 min of exposure. Also, the change in toxicity was tracked during the biodegradation process in order to appraise the environmental risk posed by the products during this process. In these assays, the toxicity was expressed as a percentage of inhibition.
Water Science & Technology
Laboratory-scale physicochemical and biological treatability studies were performed on wastewaters discharged from an industry producing household and heavy-duty detergents of powder and liquid type. The characterization of effluents led to the conclusion that the industry was highly pollutant in terms of BOD5, COD, surfactant, phosphorus, oil-grease, suspended solids and pH. By the use of lime in the precipitation stage about 80 % of COD and more than 90 % of phosphorus and anionic surface active agents could be removed. Following the treatment with lime the biodegradation of these wastewaters was investigated in continuously fed activated sludge units. The biokinetic constants of the reaction were determined as k = 0. 76 dol, K •• 972 mg/l COD, a = 0. 58 mg 02/mg COD, b • 0.044 mg 02/mg MLVSS. d. The experimental findings were used in the design of a full-scale treatment system.
Anionic surfactant toxicity and bioremediation- a methodologic review
Surfactant toxicity, remediation and associated research are often treated lightly compared to various other environmental problems, especially in various developing countries. Mostly this neglect to environmental pollutants mainly resides in its silent prevalence from household to almost all industries man comes across. We remain quite unaware of the impact of this accumulating toxicant on our daily life; affecting the entire series of the food chain and the environment. Yet to avoid surfactant use is not possible, in any point of view. Thus awareness on the safe use, disposal and remediation of surfactants gains relevance. A detailed account on the various methodologies in surfactant research is provided in this chapter, which could help biologists to evaluate the levels of surfactants in their environment. This chapter also provides concise information on the bioremediation studies of two most widely applied anionic surfactants SDS and LAS using different bacteria isolated from d...
Surfactants: toxicity, remediation and green surfactants
Environmental Chemistry Letters, 2014
Surfactants toxicity has induced a worldwide alert followed by various regulations. There are still concerns about the biodegradability and ecofriendliness of surfactants. Reviews on surfactants are available, but a concise manuscript covering surfactant types, primary and secondary toxicity of surfactants, evaluating the level of surfactant pollution worldwide, is needed. We review here the safety of surfactants in the aquatic system, in terrestrial ecosystems and for humans. We discuss strategies to solve surfactant contamination. Remediation methods include ozonation, UV radiation and catalyst-coupled auto-oxidation. We focus on the biodegradation of the anionic detergents sodium dodecyl sulfate and linear alkyl benzene sulfonate. Finally, the relevance and role of biosurfactants as alternatives to synthetic detergents are also described.
2000
A well-defined experimental system was developed to quantify the effects of a surfactant on biodegradation of ~h e n~t l~~e n e , a polycyclic aromatic hydrocarbon and model hydrophobic chemical, under two situations relevant to experimental work reported by others and to potential field applications. When phenanthrene was completely solubilized in surfactant micelles, the rate of degradation decreased with increasing surfactant concentration. However, when phenanthrene was present in excess as a solid phase, the surfactant increased the rate of microbial growth relative to a control in which surfactant was not added. The effects of the surfactant were explained well with a mechanistic model based on partitioning of phenanthrene between the aqueous phase and surfactant micelles, and on the known ability of the surfactant to increase the rate of phenanthrene dissolution from the solid phase. Such effects are expected to be observable for hydrophobic pollutants in the field as well. Whenever biodegradation is limited by mass transfer processes between nonaqueous phases and the aqueous phase, surfactants can be expected to stimulate biodegradation. The degree of stimulation for a given surfactant concentration would depend on the extent to which the mass transfer process is enhanced. It is possible, however, that a surfactant could be overdosed to the point that all of the hydrophobic compound would be solubilized, in which case a negative effect on biodegradation might occur. Thus, tests to study the potential effect of a surfactant on biodegradation in the field must consider the effects on mass transfer rates and on solubilization of the compounds of interest. Together with information on specific rates of biodegradation in the absence of surfactant, the model proposed in this study can serve as a basis for estimating biodegradation rates in the field.
Anionic surfactant biodegradation in seawater
… del Instituto Espanol de …, 1999
The authors conducted a study of the influence of several environmental factors (temperature, salinity, luminosity, aeration and the presence of sediments) on the biodegradation of a commercial anionic surfactant (LAS) in waters and sediments of Cadiz Bay (southwest Iberian Peninsula). The assay was carried out using an adaptation of the river die-away test. At temperatures of 20-25 °C, degradation exceeded 90 % within less than 10 days of assays, whereas at temperatures under 10 °C, degradation scarcely took place. Luminosity increases the degradation speed, compared with assays performed under darkness. Finally, the results show that the rate of surfactant degradation was remarkably accelerated in the presence of sediments, except in those tests where anoxic conditions were established.
Biodegradability of single and mixed surfactant formulations
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Even though detergent surfactants are mandated to be biodegradable, the environmental fate of these surfactants when mixed together in bodies of water is still not established. The study aimed to determine the biodegradability of NaLAS/CTAB surfactant combinations by measuring the amount of evolved CO2 which was measured using the OECD 301b procedure. The 90/10 and 10/90 NaLAS/CTAB systems showed a decline in biodegradation behaviors which were recorded as 55.88% and 40.12% biodegradation, respectively, after a 28-day monitoring period. Conductivity results revealed changes in the availability of ions in the system. An inflection point was observed at a CTAB concentration of 700 ppm. The highest turbidity was noted at a NaLAS/CTAB molar ratio of 1.39:1 which indicated the formation of insoluble catanionic salts in the system. Conductivity and turbidity testing revealed the formation of anionic-cationic structures such as micelles and ion-ion complexes. These structures may alter the natural degradation mechanism of microorganisms, thus leading to the slower rate of biodegradation or incomplete degradation of the surfactants.