Limboto Lake—Pentadio area is located in the province of Gorontalo on the northern arm of Sulawesi Island, Indonesia, which experienced a tectonic process from the Sula Platform collision in the mid-Miocene. This tectonic process led to the westward subduction of the early Miocene and post-collision rifting and uplifting of the arc and subduction along the North Sulawesi Trench during the Late Miocene to the Quaternary periods. The rifting process of the North Sulawesi arc resulted in the formation of the Gorontalo graben zone in the W–E direction. There are geothermal surface manifestations near Limboto Lake, such as hot spring complexes, with temperatures ranging from 74.8 °C to 78.5 °C. To understand the geological structure and prospective geothermal characteristics beneath the investigated area, we performed integrated magnetotelluric and gravity surveys. The preferred 3D resistivity model confirmed the presence of a fault system and a graben system that was filled with conductive bodies (~1–15 Ωm) corresponding to alluvium deposits. This result was in accordance with the 2D density model inferred from the gravity data, where a low-density value indicates the presence of a graben zone. The conceptual model of Limboto Lake—Pentadio was constructed using the information from the MT and gravity results, and from the geological study. The conceptual model illustrates the geothermal system in Limboto Lake—Pentadio, which is controlled by the fault system and the Gorontalo graben system.

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A high quantity of organic waste without proper waste management can endanger public health and environmental sustainability. To reduce the risk that can be caused by organic waste pollution, then there should be a solution. One of them is to make eco-enzyme. Eco-enzyme is a fermented solution from organic waste that can be used as floor cleaner, plant disinfectant, hand sanitiser, plant fertilizer, etc. A good eco-enzyme solution has special properties. One of them is the low-value power of Hydrogen (pH). In this study, other physical properties of eco-enzyme are analyzed. Eco-enzyme was produced from organic waste. Here, Sunkist orange peel and various mixtures of orange peel were used as the main materials of eco-enzyme. The eco-enzyme solutions were carried out for 33 days, accompanied by routine monitoring by reviewing physical parameters such as pH, Total Dissolved Solid (TDS), and Electrical Conductivity (EC) values. The results showed the characteristics of the eco-enzyme product by physical properties are the eco-enzyme has an acidic with a low pH value (<3.6) accompanied by high values of TDS (>1000 ppm) and EC (>1500mS/cm). The finding is TDS and EC have high value whereas usually high EC and TDS are owned by polluted liquids.