Candidate biomarkers for drinking water quality: General bacteria, Sphingomonadaceae and Microcystin (algal toxin) - degrading gene in biofilms of infiltration ponds

Abstract

One of infiltration ponds used in the preliminary step for drinking water production at Vombverket in the southern part of Sweden was set for the experiment in this study. The pond was split into two sides as one side received the source water from Vomb Lake and (untreated side). For another side, the water from the same source was pre-treated by DynaSand filter and PAC before transferred into the pond (untreated side). The study aimed to investigate the correlation between nutrients provided for bacteria in the pond and the approximate amounts of target genes representing candidate biomarkers i.e. 16S rRNA of general bacteria, 16S rRNA of Sphingomonadaceae and mlrA gene encoding microcystinase of microcystin-LR-degrading bacteria on biofilms dominated on the surface of the sand. By this reason, the sand filters operated in both sides of the pond were sampled by core samplers with the depths of 20 cm from 5 spots of each side. The sand filters were subsequently divided into three layers as top (0-10 cm), middle (10-15 cm) and bottom (15-20 cm) by the use of mini cores. Sand filter samples were extracted for DNA. Thus, DNA samples were analyzed with quantitative polymerase chain reaction (qPCR) targeting assigned candidate biomarkers.
The result showed that the treatment of source water by DynaSand filter and PAC could possibly affect the bacterial community in the infiltration pond as lower amounts of total bacteria were observed in the treated side. Also, higher proportions of bacteria from family Sphingomonadaceae, one of the candidates of bacterial group for good water quality, to total bacteria were shown in the treated side. The detection of mlrA gene was observed in some spots in both sides of the pond potentially indicating the presence of mlrA gene-carrying bacteria at the corresponding spots. In addition, it was seen that total bacteria and bacteria from a bacterial family, Sphingomonadaceae, mainly showed the highest amounts at the top layer and then the amounts decreased gradually with the depths of sand filters indicating that the top layer would mostly benefit the growth and metabolism of bacterial community in the biofilms. However, mlrA gene profile in the pond still requires the further experiments to be elucidated the presence of this gene from all the sampling points.
According to the indication of candidate biomarkers and the observed characteristics of the pond, the water in the treated side possibly showed the potential of providing the water to be used for the drinking water production with the better quality compared to the water from the untreated side. Nevertheless, the water quality in this issue could be elucidated with the data from chemical analysis as well as toxin investigation for the consideration of implementing this pre-treatment step in this study as the alternative for source water preparation in the real drinking water production.

Popular Abstract

Drinking water is described as food which requires the good handling to meet the regulation concerning the wellness of consumers. Water from the natural source is usually processed through the operation of water treatment plants and therefore supplied to households and communities. Since the use of chemicals in the processing of drinking water supposes to be minimized, biological processing by microorganisms naturally inhabiting in the water could benefit to this issue.
It is the same as the drinking water production at Vombverket, a water treatment plant in the southern part of Sweden. Here, after the water is pumped from Vomb Lake, it is transferred into the pond filled with natural sand and gravel which is called sand filters. The water would be collected under the pond in forms of artificial ground water after several months. As the water passes downwards the sand layers, the natural materials as well as algae which come with the source water would be filtered out by sand filters, herein, these substances would be utilized by microorganisms dominating in the surface of the sand in forms of biofilms through their metabolisms and biological degradations resulting in the cleaner source water for drinking water production. This step is known as artificial infiltration pond.
Apart from the operation with the infiltration pond, a continuous filter which is capable of reducing the natural substances and algae cell was also implemented to the infiltration pond. Owing to the fact that the natural matters presented in the water are served as food and growth nutrition for microorganisms, the different source water conditions would affect the level of these substances and therefore the changes of the microbial community. In this study, the biofilms of sand filters from the infiltration ponds were investigated with non-culture method by the extraction of genetic material from sand filter samples and the quantification of biological indicators with quantitative Polymerase Chain reaction (qPCR). The result showed that there were lower amounts of general bacteria in the pond where the source water was preliminary treated by the continuous filter than the ones in the pond received the water without the pre-treatment. Additionally, there were higher proportions of a bacteria group, Sphigomonadaceae, which is known as the candidate indicator for good water quality in the biofilms from the pond with pre-treated water than the pond with regular source water.
The study also revealed the presence of bacteria with the ability to break down (blue-green) algae toxin from biofilms of sand filters from the ponds with pre-treated and regular source water. However, the extensive study is needed to accomplish the prevalence of these bacteria in the pond associated with the algae toxin. To achieve the sustainability of good drinking water quality, the further research regarding human health risks such as microbial genetic material regarding antibiotic-resistance and some adverse microorganisms causing disease or outbreak should be included in the study.

• author: Buakhom, Phantira
• supervisor: Catherine Paul
• organization: Biotechnology
• course: KMBM01 20151
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• keywords: infiltration pond, applied microbiology, teknisk mikrobiologi, Candidate biomarker, biofilm, drinking water, qPCR
• language: English
• id: 7370337
• date added to LUP: 2015-10-07 11:27:30
• date last changed: 2015-10-07 11:27:30