EVALUATION OF TWO-STAGE SUBSURFACE FLOW CONSTRUCTED WETLANDS FOR ABATTOIR WASTEWATER MANAGEMENT

Abattoir wastewater is high in organic content, the waste recovery and treatment facility is expensive and this results in indiscriminate dumping into streams without adequate treatment. The effectiveness of using a two-stage subsurface flow constructed wetland to treat abattoir effluent was examined in this study. Diluted abattoir wastewater from Lafenwa Abattoir, Abeokuta, Ogun State, Nigeria was fed into a two-stage Vegetated Subsurface Bed Constructed Wetlands (VSBCW). The VSBCW consisted of 500 mm deep 10-15 mm diameter granite with 150 mm thick overlay of well graded sand planted with locally available Vetiveria nigritana. Grab samples were collected at selected points along Ogun river and measurement of physico-chemical parameters such as: Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Electrical Conductivity (EC), Total Dissolved Solids (TDS) and Total Suspended Solid (TSS) of the influent and effluent from the VSBCW were carried out. Irrigation with water and diluted abattoir wastewater to examine the variation in plant growth rate was also investigated. The results revealed a pollution load reduction as the wastewater moves away from the discharge point but inadequate to meet the FEPA (1991) standard for wastewater discharge into rivers. The VSBCW was observed to reduce the concentration of BOD5, COD, EC, TDS and TSS in the abattoir wastewater by 88.71, 87.28, 45.72, 56.89 and 72.27 % respectively. The growth rate of the V. nigritana reduced by 1.9% when irrigated with abattoir wastewater. The study revealed that locally available V. nigritana in VSBCW is effective in abattoir wastewater treatment and could be use to curtail the pollution caused by discharge of untreated wastewater into rivers.     &nbsp

LIFE-CYCLE COST ANALYSIS OF RECLAIMED ASPHALT PAVEMENT FOR SUSTAINABLE ROAD REHABILITATION

The construction of pavements requires a significant amount of non-renewable materials and energy. Recycling of asphalt pavements is a valuable approach for technical, economic and environmental reasons. The use of reclaimed asphalt pavement (RAP) is being favoured over virgin materials due to increasing cost of asphalt, the scarcity of quality aggregates and the pressing need to preserve the environment. This paper present a life cycle cost analysis of recycled pavement material for sustainable road rehabilitation on Jabulani Selepe road in Bethal, Mpumalanga Province of South Africa.  Long term cost effects of recycled materials was determined in pavement design; life-cycle cost analysis (LCCA) was carried out on recycled materials, alternative recycling materials and conventional method. The present worth of cost (PWOC) for recycling and conventional method was used to determine the most viable option for construction and maintenance. Agency cost, initial rehabilitation, maintenance, future and salvage cost while the users cost which include construction delays, accident cost, time and vehicle operating cost was done. The result showed that LCCA identifies recycled RAP as the lowest cost pavement alternative. The PWOC for RAP and alternative recycling material was 50.90% and 41.48% respectively when compared with conventional method. Thus, using large amount of RAP could turn these asphalt mixes into good alternative to hot mix asphalt in environmental terms and cost-effective means to road rehabilitation than that of a conventional project

Sustainable Non-Motorized Transport for Ga- Rankuwa and Rosslyn Transport Corridor, City of Tshwane, South Africa

A sustainable transportation system is safe, affordable and accessible. It connects different modes of transportation in order to achieve efficient movement. A sustainable transport system is one that is economical and friendly to the environment. All trips in private and public transport begin and end with walking. Non-Motorized Transport (NMT) plays a key role in completion of any journey from origin to destination. However, this mode of transport is not used optimally to enhance sustainable transport, especially where public transport is concerned. The main objective of the research was to evaluate an optimal combination of transport modes for trips made by BMW employees residing in Ga-Rankuwa north of Pretoria, in order to reduce cost of transport. The travel behaviour of BMW employees was investigated by first studying secondary data on the Municipal Household Survey (MHS) and Integrated Transport Plan (ITP) of Tshwane City. The secondary data was supplemented with primary data which was sourced by interviewing the BMW’s human resources department and conducting trip studies between Rosslyn and Ga-Rankuwa. The trip pattern of workers of BMW was evaluated to know the origin-destination, journey period and transportation cost of the trips. The movement patterns of the BMW workers were grouped into four categories. The patterns were subjected to optimization using linear programming which included the subsisting movement pattern. The trip patterns developed were based on relevant literature. The BMW workers’ movement from home to work was optimized. Their movement to work constituted a transportation challenge or problem; and was solved using simplex technique, a linear programming approach. The model was subjected to a sensitivity analysis and the results were analysed. It was found that the most patronized transportation mode for the trips between Rosslyn and Ga-Rankuwa was taxi. It was further discovered that BMW workers expended R18.47 averagely on movement from home to work through taxis. The recognition of cycling, a means of movement within short distances, allows for additional trip patterns as available options for commuters. The integration of cycling as a feeder system to trains resulted in 36% trip cost reduction for the commuters. The research revealed that while less than 45% of the employees may continue to use the present scenario, more than 55% of the employees may use a combination of cycling and trains. The study suggested that similar work should be done to cover other economic and important routes in order to encourage the use of cycling as a link to other transportation modes in other industrial areas of the City of Tshwan

IMPROVING THE STRENGTH PROPERTIES OF SUBGRADE SOILS WITH FLY ASH

Subgrade soils encountered during road construction are not always good materials to respond to the imposed stresses which has become a dominating factor for the failure of pavements in Nigeria. The subgrade materials were sourced from three locations within South Africa namely, Heanertsburg Village (A), Laudium, South West of Pretoria (B), and Eskia Mphahele drive to Francis Baard Street, Pretoria (C). Fly Ash (FA) was added to samples A, B, and C at 3-12%, 5-15%, and 9-12% respectively. Sieve analysis, compaction, Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) tests were conducted on the virgin and stabilized soil samples for a curing time of 1, 7 and 28 days. The soils were classified as A-7-6, A-6 and A-2-6 according to AASHTO for samples A, B and C respectively. UCS and ITS was improved with the addition of FA to all the soil samples. The UCS results for sample A (406 kN/m2) and B (625 kN/m2) falls short of 1710 kN/m2 specified for cement stabilized base materials but 12% and 10% FA treated soils may be used as improved subgrade for flexible pavement construction. However, sample C result meets the requirement of 687-1373 kN/m2 for sub-base at 100% relative compaction. All the stabilized samples increase in ITS with respect to increasing curing days and FA. Only sample C attained to the specified ITS value. Therefore, FA can be used to improve the subgrade in order to withstand the imposed stress

CHARACTERISTICS OF GLASS FIBRE REINFORCED ASPHALT CONCRETE FOR HIGHWAY PAVEMENT DURABILITY

Fibres have been reported to improve the performance of asphalt against some pavement distresses and have the potential to improve the cohesive and tensile strength of asphalt. Laboratory investiga-tion of the characteristics and properties of glass fibre reinforced asphalt was conducted. Specimens were produced and tested for Stability using Marshall Test. The optimum bitumen content for the con-trol was also determined. Glass fibre of 12 mm length in the range of 0.2 – 0.8% by weight were added to the mix, volumetric parameters were examined using Asphalt Institute specification. Voids in Total Mix was used to determine if there is significant difference in the mean using one-way ANOVA at 5% probability level. The result showed that the penetration of the modified bitumen are lower and there is increase in the optimum bitumen content when compared with the control. Voids in mineral aggregate decreases by 2.72, 1.60, 5.92 and 6.98% when 0.2, 0.4, 0.6 and 0.8% fibre respectively were added. Voids in total mix for both the control and modified asphalt showed no significant difference. The volu-metric parameters falls within the specification. The modified glass fibre would greatly enhance the durability and longevity of highway pavement structures