Sustainable sound waste management startegies in Juja, Kenya

Integrated solid waste management includes source reduction, source separation, recycling and reuse as well as materials recovery. The waste materials that remain should be safely disposed into a sanitary landfill. Up to 2010 when this study was done, no Kenyan city had a sanitary landfill and solid waste piles along inner city streets was a common sight in  Nairobi. This study found that the solid waste in Juja consisted of 80% food and other organic wastes, 10% plastics, 2% metal and glass, and 3% mixed refuse. The waste had a very low level of toxic substances. The majority of the households produced less than 3 kg per day, which translated to less than 0.5 kg/person/day. JKUAT-SWMM, a solid waste management model developed in this study, suggested that if 25% of the population would do composting using household compost digesters of 288 L, the area of a disposal site required for 1 million people would be 16 ha. The identified site was on fallow land that received an annual rainfall of 600-800 mm. A waste disposal facility in Juja Farm could cater for most ofthe towns in the area of interest, including Juja, Mangu, Kimunyu,  Gatundu, Thika, Ruiru and Kahawa. The landfill would be accessible to institutions such as Jomo Kenyatta University of Agriculture and Technology in Juja, Mount Kenya University in Thika, Kilimambogo Teachers’ College in Kilimambogo, and numerous secondary schools in the area

Performance evaluation of sand dams as a rural rainwater conservation and domestic water supply technology in East-African drylands, a case-study from South-Eastern Kenya

AbstractSand dams (SDs) are rainwater harvesting methods in East-African drylands for rural water supplies and small-scale irrigation practices. However, little information exists on their ability to maintain the harvested water in the right quantity and quality. Three SDs were selected from south-eastern Kenya’s semi-arid zone as a case study to evaluate their operational performance. Water and sediment samples were collected and analyzed in both the field and laboratory. Six performance indicators, namely stormwater-capture efficiency (SCE), water-saving efficiency (WSE), volume-based and time-based reliabilities, water demand satisfaction rate (WDSR), water loss percentage, physicochemical water pollution index (WPI) and microbial non-compliance rate (NCR), were computed. Results showed that water storage in SDs is quite low and unfit for direct human consumption. In fact, three experimental SDs harvested 7,356 m3 during the long-rains season (March–May 2018) for an estimated water demand of 8,990 m3 (June–September). About 4,505 m3 (61.24%) was lost through evaporation (64.11%) and seepage (35.89%). These SDs exhibited low WDSR (31.72%), inadequate SCE (3.09%), low WSE (30.85%), dismal volume reliability (24.56%), and undependable time reliability (24.91%). Shallow-well water was less polluted than scoop-hole water but both didn’t meet the bacterial water quality standard (0 CFU/100 mL). The former scored a low WPI of 1.86 (reasonably clean) compared to clean water (WPI ≤ 1), while the latter scored a high WPI of 12.91 (considerably polluted). Furthermore, NCRs for total coliforms were 60% in shallow wells and 90.79% in scoop holes. Therefore, this water should be treated and disinfected for domestic use

Effects of Land Use and Land Cover Change on Potential Ecosystem Service Value in Mathioya Watershed, Murang’a County, Kenya

Wetlands in Mathioya watershed are declining due to continued alterations caused by human and natural factors. This study assessed the effects of spatiotemporal changes in Land Use and Land Cover (LULC), on potential ecosystem service value in Mathioya watershed, Murang’a County, Kenya. We considered the period between 1987 and 2020. Supervised classification using maximum likelihood classifier was performed in ERDAS imagine v.15. The values obtained from the analysis of LULC maps were then used together with the global data for habitats to approximate the ecosystem service value (ESV) change within the watershed. Six LULC classes namely, forestland, wetlands, agricultural land, water bodies, built-up areas and barren lands, were identified. Analysis of Landsat images revealed that between 1987 and 2020, human activity led to decrease in the area covered by wetlands, forestland, water bodies, and barren land. Area under these land cover classes decreased by 45%, 34%, 50% and 27%, respectively. During the study period, agricultural land and built-up areas increased by 43% and 85%, respectively. Changes in LULC resulted in decline of ESV from $368.5 million/ha/year in 1987 to$337.7 million/ha/year in 2020. With respect to individual ecosystem services, regulating services declined. Between 1987 and 2020, water regulation and climate regulation declined by 48% and 16%, respectively. However, provisioning services such as food production increased by 34%. Wetlands play a critical role in the provision of ecosystem services. The loss of wetlands translated to decline of critical ecosystem services such as water regulation. Eventually, this will lead to poor water quality within the watershed and the entire County, thus impacting negatively on the health of the locals. Hence, there is a need for urgent action to prevent the current trend of wetland loss within Mathioya watershed

MATHEMATICS FOR SPECIFICATION AND DESIGN: THE PROBLEM WITH LIFTS . . .

The use of mathematics in the specification and design of practical software systems is discussed. As an example, the formal specification and design of a multiple lift (elevator) system is described, using the notations of Communicating Sequential Processes