Dr. Dalit Vaizel Ohayon, National Bacteriologist, Central Lab, Mekorot
Partners:
Dr. Oded Swad, Dr. Dana Atiya Glikin, Ram Cohen, Tzahi Zvi, Mekorot
Prof. Ariel Kushmaro, Prof. Eitan Ben Dov, Shimrit Leor and Liran Bogoslavski, Ben-Gurion University
Dr. Yakir Ofir, Dr. Rafi Pas, Rami Nehushtan, Dr. Yossi Geva, Israel Institute for Biological Research
February 13, 2016
Clogging in active wells in Israel and around the world is a common water drilling problem in general, and specifically when the water is rich in sulfur and iron. Clogging can trigger processes such as aerobic clogging or anaerobic corrosion (see image 1). When testing the sealant, diverse microbiological populations were found to be incorporated into the sediments. These include iron, calcium, sulfate, carbonate and clay. Clogging causes a decline in flow discharge rate, may halt well operations, and involves significant expenses. Cleaning the wells is conducted periodically or following a decline in the relative flow rate. During the cleaning process, wells operations must be halted and pumping equipment dismantled. The cleaning process sometimes indirectly causes an increase in the quantity of bacteria and formation of new biofilm in a relatively short period of time.
Image 1: a. schematic drawing of the groundwater well structure; b. a photo of a screen that has been clogged and ruined due to clogging and corrosion
In the past, there were no efficient tests available to identify and quantify bacterial populations involved in biofilm formation. In addition, there were no efficient methods for prevention and treatment of biological fouling caused by bacteria. Today, there is increasing awareness of the need to specify the causes, sources and processes involved in clogging at well sites and of the importance of finding safe, efficient prevention and treatment methods. In Israel, clogging is especially common at well sites in the Arava region, which suffers from water shortages regardless. There is a need for in-depth research that can help solve clogging problems and thus increase the water supply to this arid region. This study specifies the bacterial populations that contribute to clogging in Arava well sites, and studies clogging and biofilm formation mechanisms.
The goal of this study is to obtain a deep understanding of biofouling formation at well sites. This knowledge can contribute to development of biofilm prevention mechanisms and treatments. By developing treatment methods, abandonment of well sites due to clogged screens can be avoided; hydraulic yield can be improved; preventive maintenance programs can be implemented at the sites; renovation costs can be reduced; alternative solutions for clogging problems can be identified; and bacterial anomalies caused indirectly during cleaning processes can be avoided. These anomalies occasionally require drilling to be halted.
In order to conduct this study, Mekorot collaborated with researchers from Ben Gurion University and from the Institute for Biological Research. The study used molecular methodology to identify bacteria populations by deriving nucleic acid from the samples, enhancing the rRNA gene 16S using PCR technology and employing advanced DNA sequencing methods (NGS – New Generation Sequencing). Bacteria populations were identified during renovations of six well sites – Hatzeva 7, Hatzeva 15, Idan 2a, Idan 5, Idan 11 and Grofit 4 (see Table). In the lab model systems, controlled experiments were conducted in order to study biofilm formation mechanisms using bacteria that were isolated during drilling. At the same time, a laboratory model was constructed with a screen similar to those used in the well and surrounded by soil taken from the heart of the well site. In addition, coupons made of glass, stainless steel and iron were inserted in order to test initial biofilm formation rates and composition. We are currently using the systems in this model to explore methods for prevention of biofilm formation by changing mineral composition and ventilation conditions and adding materials that delay biofilm formation.
Clogging is a well-known phenomenon all over the world but the quality of the water that is drawn in Israel accelerates the problem. As a result, research on the situation in Israel can serve as an accelerated model for researchers worldwide to be used to track the various stages of clogging. This study presents knowledge accumulated so far about bacteria that is involved in the formation of biofilm which causes clogging.
Possible solutions being considered for prevention of biofilm formation are coating the screens or incorporating materials that can inhibit multiplication of the various bacteria that cause clogging.
Table: The most common species found at sites Hatzeva 7 (H7 and H7S), Hatzeva 15 (H15), Idan 2a (I2), Idan 5 (I5), Idan 11 (I11) and Grofit 4 (G4). This table shows their distribution per site.
