Evaluation of sediment solidification ability using in situ microbial functions in Ichkeul Lake, Tunisia

Abstract

The merit of exploiting ecosystems is debated globally. There have been harmful effects due to water resource management of the world natural heritage site at Lake Ichkeul, Tunisia. These concerns have increased the interest in the production of natural minerals. Natural minerals, such as calcite, are produced from in situ microorganisms and are categorized as construction materials. They are considered to be a viable alternative new resource. This study focused on the physical and biological properties of sediments from Ichkeul Lake and the potential of calcite precipitation from in situ microorganisms in these sediments. The results of field investigations focused on high-salinity aquatic plants (Ruppia cirrhosa) that were distributed in the eastern portion of the lake. These results show that the area around the Tinja channel had increased salinity in the dry season. The element contents were measured with portable X-ray fluorescence (XRF). Ichkeul Lake sediments had higher calcium content than standard Japanese samples. This suggests that microbial carbonate precipitation is applicable to Ichkeul Lake. Calcite precipitation techniques, such as acceleration of urease-producing bacteria, were studied. Pre-cultivation tests focused on increasing urease activity rates from in situ bacteria. Solidification of sediment resulting from enhanced calcite precipitation rates through use of urease-producing bacteria was examined. All of the sediment samples from Ichkeul Lake were able to precipitate calcite. The results of the field investigation and laboratory tests indicated that the area around the mouth of the Joumine River showed an enhanced calcite precipitation rate after a cultivation period of 1 month under high-salinity conditions.