Water quality indexes are a tool used to evaluate the physicochemical characteristics of a water body according to its use. The present study proposes the inclusion of oil and grease (OG) as a new water quality index (ICAM_PFF-GA) parameter for the preservation of marine biota in tropical areas, since it is a typical pollutant found and measured in water bodies, causing damage to the aquatic environment. The normalized curve for OG was defined based on the percentage of surviving microorganism under a lethal concentration exposure of OG. The ICAM_PFF-GA suitability was evaluated by its application to analyze marine water quality in the area of the sea outfall in the city of Cartagena, Colombia and comparing the trends of the outfall flow and the rainfall for 2017. Physical chemical data analyzed for the year 2017 shows that OG varies from 0.0 to 3.8 mg/L. The results show that the water quality index increases when rainfall and flow values increase for the rainy season. The ICAM_PFF-GA can be a tool to evaluate the water quality of marine waters affected by the discharge of waters with oil and grease.

The Cartagena Bay in Colombia has vital economic and environmental importance, playing a fundamental role in both the port and tourism sectors. Unfortunately, the water quality of the bay is undergoing a deterioration process due to the significant influx of sediment from the artificial channel known as Canal del Dique. Although field campaigns are carried out semiannually with 12 monitoring stations to evaluate these impacts, understanding the spatial dynamics of suspended solids in the bay remains a challenge. This article presents a spatial analysis of water turbidity in the Cartagena Bay during the years 2018 to 2022, using Sentinel-2 images. To achieve this objective, an empirical algorithm was developed through the Monte Carlo simulation. The validation of the algorithm demonstrated an R-squared value of 0.83, with an RMSE of 2.72 and a MAPE of 24.93%. The results showed the seasonal variability, with higher turbidity levels during the rainy season, reaching up to 35 FNU, and lower turbidities during the dry season, dropping to 1 FNU. Furthermore, these findings indicated that the southern area of the bay presents the most significant turbidity variations. This research enhances our understanding of the bay’s turbidity dynamics and suggests an additional tool for its monitoring.

Characterizing inherent optical properties (IOPs) of water constituents is crucial for remote sensing applications. Remote sensing in Cartagena Bay is particularly challenging due to significant variations in constituent concentrations caused by the seasonal and annual variability of discharges from the Canal del Dique. This article presents the variability in absorption coefficients of phytoplankton, chromophoric dissolved organic matter (a_CDOM), and non-algal particles (a_NAP) in Cartagena Bay. Absorption coefficients were measured in the laboratory across multiple monitoring campaigns, with seasonal analyses conducted to establish relationships between absorption properties and biogeochemical parameters such as chlorophyll-a, salinity, and turbidity. Results indicate that at 440 nm, a_CDOM and a_NAP primarily dominate absorption during the rainy season, while a_NAP dominates during the dry season. This variation is influenced by inflows from the Canal del Dique. Lower CDOM absorption in 440 nm (a_CDOM440), and higher CDOM absorption slope (S_{CDOM275–295}) and higher salinity values were observed during the dry season, which is consistent with the reduced fluvial influx. Spatial variability shows that higher CDOM values prevail in the river plume area during both seasons, with particularly higher values in the rainy season. Median values of a_NAP were similar in both seasons, with a strong relationship found between all a_NAP data and turbidity (rp = 0.785). Compared to other estuaries, Cartagena Bay exhibits optical characteristics typical of a coastal water body subjected to river discharges, including the elevated turbidity and the high dissolved organic matter influenced by significant inflow from the Canal del Dique. These features highlight the bay’s dynamic interactions with terrestrial inputs. This study provides invaluable information on the optical characteristics of Cartagena Bay, which is crucial for improving the accuracy and effectiveness of remote sensing models for optically active parameters such as turbidity, suspended solids, CDOM, and chlorophyll-a.

Landfill leachate in developing countries is often discharged into the environment without treatment because most treatment technologies have high costs and are highly complex, making their implementation infeasible. This research evaluates the technical feasibility of implementing constructed wetlands with horizontal subsurface flow for the treatment of raw leachate and leachate pretreated with photo-Fenton of the Loma de los Cocos landfill in the city of Cartagena, Colombia. In order to evaluate the vegetation performance, three wetland modules were constructed: one without vegetation (HC), one with Rhizophora mangle (HM), and one with Typha latifolia (HE). Two tests were performed: one with raw leachate and another using pretreated leachate with photo-Fenton, which is considered a suitable treatment for little or moderately biodegradable waters. The modules were operated with a hydraulic retention time of 8 days and an operating time of 16 days. For the photo-Fenton pretreatment, the pH of the leachate was adjusted to values between 2 and 3 using a molar ratio ${\mathrm{Fe}}^{2+}/{\mathrm{H}}_2{\mathrm{O}}_2$ of 0.6 at a retention time of 40 minutes. The raw leachate was characterized as having chemical oxygen demand (COD) concentrations between 3,000 and $\mathrm{4,800}\mathrm{mg}{\mathrm{L}}^{-1}$ and pH values above 7.5. In general, wetlands had higher efficiencies with pretreated leachate. The effluent COD concentrations obtained in all tests complied with the maximum limit established by current Colombian regulations ($\mathrm{2,000}\mathrm{mg}{\mathrm{L}}^{-1}$ ). During the pretreated leachate test, the HE constructed wetland had pollutant removals that were slightly higher than the mangrove sown wetland (HM): COD (HE: 77%; HM: 73%), chloride (HE: 58%; HM: 50%), sulfate (HE: 58.6%; HM: 54.5%), nitrite (HE: 54.7%; HM: 67%), nitrate (HE: 98.4%; HM: 90.5%), and TDS (HE: 56%; HM: 54%). Although the HM wetland had removal average efficiencies that were slightly lower than those of the HE wetland, it can be concluded that horizontal subsurface-flow constructed wetlands with both vegetation are a viable alternative for the treatment of leachate from the Loma de los Cocos landfill.

The valorization of drinking water treatment sludge (DWTS) and eggshell waste represents a promising route for reducing landfill disposal and developing alternative stabilized materials for geotechnical applications. This study aimed to evaluate the mechanical and microstructural behavior of DWTS stabilized with commercial lime (CL) and eggshell-derived hydrated lime (EHL), including alkali-activated EHL systems. EHL was produced from locally collected eggshell waste through washing, drying, grinding, calcination at 1000 °C for 4 h, hydration, drying, and sieving. The mixtures were prepared with lime contents of 5%, 8%, 11%, and 14%, while NaOH solutions of 0.5, 1.0, and 1.5 M were used for the activated systems. A total of 120 cylindrical specimens were compacted under controlled dry unit weight and moisture content and cured for 7 and 28 days. The stabilized DWTS was evaluated through unconfined compressive strength (q_u), SEM–EDS analysis, and multifactorial ANOVA. The highest q_u for CL-treated specimens was 4561.72 kPa at 14% lime and 28 days, while EHL reached its best response at 11% lime and 7 days, with a q_u of 3195.13 kPa. In general, EHL showed a competitive performance at intermediate and high lime contents, although increasing NaOH molarity tended to reduce strength.

The management of sludge generated during drinking water treatment poses an environmental challenge due to the large volumes produced and the associated disposal costs. This study evaluates the potential use of sludge from the El Bosque Drinking Water Treatment Plant (Cartagena, Colombia) as a partial replacement of fine aggregate in concrete production. The sludge was characterized through physical, chemical, mineralogical, and microstructural analyses, including particle size distribution, Atterberg limits, specific gravity, X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and petrographic examination. Five concrete mixtures were produced by replacing the fine aggregate with sludge at 0%, 5%, 10%, 15%, and 20% by mass. Mechanical performance was assessed through compressive strength and splitting tensile strength tests at curing ages of 7, 14, and 28 days. The results showed that increasing sludge content led to a progressive reduction in mechanical strength. Nevertheless, the mixture containing 5% sludge achieved a 28-day compressive strength of 26.15 MPa, corresponding to 96.9% of the design strength and comparable to the control mixture. Microstructural analyses revealed that higher sludge incorporation levels increased porosity and microcracking while reducing the relative proportion of cementitious matrix, explaining the observed decline in mechanical performance. These findings demonstrate the technical feasibility of incorporating DWTS from the El Bosque Drinking Water Treatment Plant as a limited replacement for fine aggregate without substantial losses in mechanical performance. The study provides site-specific physicochemical, mineralogical, and microstructural information that supports the sustainable valorization of this locally generated residue within circular economy strategies for the construction sector.