Remediation of anionic surfactants and ammonium by biological materials

Abstract

Surfactants are the main components in detergents and they are primarily discharged from household and industry. Ammonia (or ionized form ammonium) is a byproduct of animal and human metabolism and it is formed in and discharged from aquaculture. Contamination of soil and water sources by surfactants and ammonium is becoming a big problem because of their harmful effects. These substances are highly toxic to many organisms, leading to possible mass deaths in the freshwater ecosystem. As their presence causes a potential environmental risk, industrial and household wastewater systems should be adequately treated to reduce the concentration of ammonium and surfactants. Chemical and biological methods are primarily used to treat wastewater systems. Biological treatment methods are more eco-friendly in comparison to chemical methods. Among biological treatment methods, the use of specific bacteria strains for removal of chemical contaminants is a widely applied process for treatment of industrial and municipal wastewater. However, those bacteria may not be capable of withstanding harsh environmental conditions or they may not specifically degrade the contaminant of interest, so isolation of bacterial strains more resistant to environmental extremes and more suitable for bioremoval is a possible strategy to improve current wastewater treatment strategies. By isolating bacteria well-adapted to the environmental and physical conditions of the system to be cleaned, very high efficiencies can be obtained for wastewater cleaning. To this end, a two-step approach was used. In the first part of this project, our aim was to find an integrated efficient biological based method to clean up industrial wastewater from anionic surfactants. Two main strategies were utilized to solve this problem: Finding and applying a more biodegradable and eco-friendly detergent alternative, and developing a biological treatment method specific for the anionic surfactants in the wastewater system of interest. It is expected that, by combining these two strategies, anionic surfactants in wastewater can be removed more efficiently. In the second part of this project, a novel bacterial strain, which we termed STB1, was isolated from a commercial sea bass farm and found to display high heterotrophic ammonium removal characteristics. The species identity of STB1 was determined to be Acinetobacter calcoaceticus. We evaluated ammonium removal characteristics of STB1 at varying ammonium concentrations, and observed that STB1 can almost completely remove ammonium at low (50 mg/l) and medium (100 mg/l) concentrations within 72 h, while 45% ammonium removal was observed at a higher concentration (210 mg/l) during the same time period. Trace amounts of metabolized ammonium was converted to nitrite or nitrate and 22.16% of ammonium was introduced to cell biomass, while 4.34% of total nitrogen was initially incorporated into biomass and subsequently released to the supernatant fraction in the 100 mg/l sample. Most of the remaining conversion products are expected to be gaseous denitrification products. Toxicological studies with Artemia salina (brine shrimp) nauplii revealed that STB1 strain is non-toxic to Artemia larvae, which suggests that STB1 can be safely and efficiently utilized for water quality enrichment in aquatic ecosystems.