Jonah Chukwuemeka Agunwamba

Rapid urban growth in the Global South makes it harder to choose infrastructure corridors, especially in sensitive coastal basins. This study introduces a spatial decision-support framework tailored to local conditions. It combines the Delphi technique, Analytical Hierarchy Process (AHP), and Geographic Information Systems (GIS) to improve sanitary landfill site selection in Uyo and nearby areas in South-South Nigeria. The region sits on the highly permeable Benin Formation and gets heavy annual rainfall of 2,500 mm. Ten environmental experts participated in a three-round Delphi process to agree on key parameters, which were subsequently measured using a pairwise AHP matrix to ensure consistency (CR < 0.10). Hydrogeological factors, mainly Lithology and Soil Permeability (31.4%), were given the greatest weight, followed by infrastructure and proximity factors. Using Weighted Linear Combination (WLC), the spatial analysis showed a strong urban buffer effect: only 210.5 km ² (9.2%) of the 2,289.41 km ² area is classified as “Highly Suitable” for engineering, mostly in remote parts of Ikono, Ibiono, Uruan, and Etinan. The rest of the land is limited by required exclusion zones around growing peri-urban homes (1,000 m) and surface drainage networks (500 m). The model was checked with fifteen independent ground-truth points, showing an overall accuracy of 86.67% and a Cohen’s Kappa coefficient (ǩ) of 0.762, which means there was strong spatial agreement. The findings show that standard site selection methods often underestimate aquifer risks in tropical sedimentary areas. The protocol developed here offers a practical framework for infrastructure planning in humid, vulnerable regions with limited data.

Stepped spillways are engineered structures designed to mitigate the erosive effects of floodwaters on downstream riverbeds. Despite extensive research on spillways with slopes exceeding 26.6°, there is a notable gap in understanding energy loss mechanisms for slopes between 3.4° and 26.6°. This study aims to develop predictive models for energy dissipation in stepped spillways within this slope range, eliminating the need for complex friction factor calculations. Experimental data from air-water flow experiments on a large-scale stepped spillway facility inform the development of these models. The proposed models demonstrate strong correlation with experimental data (R = 0.79 - 0.99), offering a simplified and accurate approach to estimating energy losses.

This study focuses on developing a climate-flood model to investigate and interpret the relationship and impact of climate on runoff/flooding at a sub-regional scale using multiple linear regression (MLR) with 30 years of hydro-climatic data for the Cross River Basin, Nigeria. Data were obtained from Nigerian Meteorological Agency (NIMET) for the following climatic parameters: annual average rainfall, maximum and minimum temperatures, humidity, duration of sunlight (sunshine hours), evaporation, wind speed, soil temperature, cloud cover, solar radiation, and atmospheric pressure. These hydro-meteorological data were analysed and used as parameters input to the climate-flood model. Results from multiple regression analyses were used to develop climate-flood models for all the gauge stations in the basin. The findings suggest that at 95% confidence, the climate-flood model was effective in forecasting the annual runoff at all the stations. The findings also identified the climatic parameters that were responsible for 100% of the runoff variability in Calabar (R² = 1.000), 100% the runoff in Uyo (R² = 1.000), 98.8% of the runoff in Ogoja (R² = 0.988), and 99.9% of the runoff in Eket (R² = 0.999). Based on the model, rainfall depth is the only climate parameter that significantly predicts runoff at 95% confidence intervals in Calabar, while in Ogoja, rainfall depth, temperature, and evaporation significantly predict runoff. In Eket, rainfall depth, relative humidity, solar radiation, and soil temperatures are significant predictors of runoff. The model also reveals that rainfall depth and evaporation are significant predictors of runoff in Uyo. The outcome of the study suggests that climate change has impacted runoff and flooding within the Cross River Basin.

This research investigated the use of biodegradability of sewage in ordinary pit latrines to assess the performance of such sewage for agricultural purposes. The objective of this paper therefore was to study the biodegradability of faeces in selected pit latrines that would lead to the assessment of the performance of such pits. Both aerobic and anaerobic biodegradability of pit sludges were thus measured. Samples of fresh faecal sludges collected from pit latrines in selected households in Aku community were subjected to laboratory analyses for their physico-chemical and biological characteristics. The results showed that in terms of biochemical oxygen demand (BOD), twelve (12) pits had biodegradability of 80 Parsant and above. In the case of chemical oxygen demand (COD) and suspended solids (SS), nine (9) pits had biodegradability of 80 Parsant and above. For the volatile solids (VS), eleven (11) pits had biodegradability of 80 Parsant and above. Ten (10) pits had ratio of volatile solids to total solids (VS: TS) ranging from 0.90 – 2.93. Using COD: BOD ratio, eleven (11) pits had values ranging from 0.90–1.34 indicating that the pits sludges were readily biodegradable and good for agricultural purposes. Lower values showed lower organic contents and lower biodegradability and therefore unsuitable for agricultural purposes. High COD: BOD, VS:TS ratios should therefore be used to assess the performance of pit latrine sludges for higher agricultural productivity considering good user-behaviour, favourable soil and environmental conditions. Excreta collected from such pits should be used to enhance soil fertility.

There have been several incidences of flood recently, which are believed to be aggravated by increased climatic variables as a result of perceived changes in climatic conditions (due to climate change) in the Cross River Basin. The basin is the most extensively developed and used river basin in the management of the water resources of the Cross River and Akwa Ibom States in Nigeria. In this paper, 30 years (from 1992 to 2021) of hydro-meteorological data (annual average rainfall, maximum and minimum temperatures, hu midity, duration of sunlight (sunshine hours), evaporation, wind speed, soil temperature, cloud cover, solar radiation, and atmospheric pressure) from four stations in the Cross River Basin were obtained from the Nigerian Meteorological Agency (NIMET), Abuja and subjected to trend detection analysis using the Mann–Kendall test to determine the trend in climatic parameters. The results indicate that there is a significant upward trend in annual rainfall in Ogoja but a downward trend in Calabar. The evaporation trend is significantly downward in Eket, whereas in Calabar, there is an upward trend in solar radiation. Generally, there is a significant rise in annual maximum temperature across the basin. Serial correlation and segmented regression analyses were performed to measure the impact of fluctuations in monthly and long-term Tahiti and Darwin’s Sea level pressures on the climatic variables at the Cross River Basin catchment. These analyses were necessary to determine the extent of the influence of the El Nino Southern Oscillation climatic cycle. The analyses show no significant association between the El Niño Southern Oscillation (ENSO) and rainfall or between the ENSO and runoff in the catchment. This implies that the impact of the ENSO on rainfall and runoff in the Cross River Basin catchment is not considerable. The intercepts derived from the segmented regression in Eket and Ogoja show significant positive trends in both areas for rainfall and runoff. The trends in intercepts suggest that there are external factors influencing rainfall and runoff other than ENSO events, thus strengthening the assertion of climate change. Results from this study will facilitate the understanding of the variability in climatic parameters by stakeholders in the basin, researchers, policymakers, and water resource managers.

Rainfall intensity–duration–frequency (IDF) relationships are crucial in the design and management of hydraulic structures. At the core of the assumption for IDF development is that the statistics of past rainfall events will represent future rainfall events. It has been proven that climate change is a major trigger for non-stationarity; therefore, the assumption is untenable. This work is aimed at considering the impact of climate change in the development of IDF curves for a city. To account for this non-stationarity, an RCM was combined with measured data through a climate factor (CF) to develop a rainfall IDF for the coastal city of Calabar. The baseline and future climatic periods of the RCM were 1971–2010 and 2021–2060, respectively. The annual maxima series (AMS) were disaggregated and fitted to the Gumbel distribution. Results revealed that the magnitude of trend for the measured AMS and measured annual rainfall are −0.351 and +3.628, respectively. A CF value of 0.86 was obtained, and a generalized non-stationary rainfall IDF model was derived. When compared to models from similar studies, this model has conserved values with r² = 1 and an error margin of ±6% for all return periods. This will introduce economy in the design of hydraulic structures. Excess runoffs in Calabar were, therefore, related to frequent short-duration rainfall with low intensities.

The arousal of environmental concerns due to spike in environmental degradation has necessitated proper waste management and disposal. Arsenic, a potentially toxic element in cassava wastewater, requires treatment prior to the wastewater disposal to minimize environmental pollution and associated health implications. The present study thus addressed the treatment of As⁵⁺ heavy metal in cassava wastewater using an efficient biosorbent from chemically pretreated unshelled Moringa oleifera seeds. The effect of various factors influencing the biosorption process for arsenate removal was studied including pH, contact time, biosorbent dosage, and biosorbent pretreatment concentration. The results of Fourier transform infrared spectroscopy clearly suggested that additional functional groups attributed to esters were formed in the pretreated biosorbent, which is responsible for improvement in biosorption. It was found that contact time, biosorbent dosage, and biosorbent pretreatment concentration had statistically significant effect (p values < 0.05) on arsenate removal. A maximum percentage removal of 99.9% was achieved in the synthetic solution at pH 4.0, contact time of 30 min, and dosage of 2 g for biosorbent pretreated with 1 M of chemical solution. Furthermore, through isotherm and kinetics studies, it was discovered that the biosorption process for untreated biosorbent is by ion exchange, while that for treated biosorbents indicated a multifarious adsorption mechanism. Moreover, the biosorption process was exothermic and spontaneous. Also, it is noted that the sorption capability of the biosorbent increases with pretreatment concentration. A statistical model has been developed with prediction R² of 0.898, which incorporates the effect of treatment concentration on the percentage removal of As⁵⁺ from cassava wastewater.

Faecal sludge deposited into the pit latrine is subject to biodegradation. The aim of this research was to develop model for the filling rate of faeces in ordinary pit latrine together with the effect of shape factor on such fillings to prepare the minds of users on the filling characteristics of the pit based on contents, usage and environmental factors. Consequently, faecal sludges sampled from 100 pits already filled were subjected to laboratory analyses for their physico-chemical and biological characteristics. Models for the actual filling rate of faeces in ordinary pit latrines were derived using BOD, COD, VS, and TS data, calibrated and verified. For a more critical situation, models were also derived for the filling rates considering pit shapes that gave the actual pit filling in comparison with the general condition. From the results, the actual filling rate was lower than those obtained using BOD, VS and TS. However, the COD gave filling rate closer to the actual filling rate than other parameters since TS could not be used to assess the filling rate of faeces in pit latrines. The pits exhibited low filling rate in terms of BOD in 2 pits. In terms of COD, the filling rate was higher compared with that of BOD. Low filling rate was observed with volatile solids and only 3 pits exhibited moderately high filling rates whereas total solids had the highest number of pits with high filling rates. The filling rates for both the square and rectangular pits increased by 26.5% from 40 – 90 ℓ/capita/year to 50 – 112 ℓ/capita/year due to the shape factor and this was above the values obtained in existing models while that of the circular pit remained the same. Reduction in pit volume and increase in filling rate by faeces was due to dead corners as a result of clogging, thereby reducing the area available for faecal infiltration into the surrounding soil. Circular pits are more stable because of the natural arching effect of the ground around the hole and there are no corners to concentrate the stresses. Pits with flat sides are much more likely to develop clogging resulting to dead corners than the circular pit. From this study, it is therefore evident that the shape of pit latrine determines the actual volume and the filling rate of faeces in pit latrine taking into consideration geological and environmental factors. Thus for optimal design, our engineers should take note of the pit shape factor. Thus, the model can be used to determine the filling rate of ordinary pit latrines considering soil characteristics, ground conditions and other favourable conditions.

Specific models for the rational design of pit latrines of different shapes and sizes are presently non-existent. What exist are general design models irrespective of the shape and size of latrine which may not give the actual design parameters needed. This research was limited to the derivation of models that will aid the design of the capacity of pit latrines of different shapes and dimensions for different population of users and under different soil formations and ground conditions. The objective of this research was to derive models for the rational design of pit latrines of different shapes using data collected from 500 different household pit latrines already filled up. Thus, models were derived for different latrine pit shapes and sizes using data collected through the administration of designed questionnaire on 500 households having pit latrines already filled up. Models were developed specifically for different latrine shapes whereas those of other researchers were generalized. These models were calibrated and verified for the rational design of pit latrines of different shapes and sizes. The regression coefficients for calibration were 0.75, 0.65, and 0.50 and for verification are 0.97, 0.98 and 0.99 for square, circular and rectangular pits respectively. The implication of this research is availability of design models for the construction of different pit latrine shapes.

There is limited information about the characteristics of faecal sludges in ordinary pit latrines. Knowledge of the physico-chemical and biological characteristics of pit sludge from different layers of the pit apart from providing an indication of the nature of pit contents endeavoured to provide information and decision support for managing pit latrines during their normal lifespan. Therefore, this paper was aimed at investigating the physico-chemical and biological characteristics of pit sludge samples to equip latrine owners with environmental and health implications of this sludge. Legislation that establishes regulations specifically for the treatment and discharge, enduse, or disposal of faecal sludge is therefore essential. Thus, faecal sludges sampled from ten (10) pit latrines were subjected to laboratory analyses with particular reference to selected parameters. From the study, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), moisture content, suspended solids (SS) and volatile solids (VS) showed decreasing trend throughout as the pit depth increased. Temperature presented double scenarios, increasing initially and decreasing afterwards with the highest values within 0.4m to 0.6m pit depth in all the pit latrines. Efforts to understand and mitigate the health effects of particulate matter (PM) air pollution have a rich and interesting history. This review focuses on six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There has been substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonary health. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.