USE OF DRILL CUTTINGS ASH AS STABILISING AGENT FOR SELECTED NIGER DELTA SOILS FOR ROAD CONSTRUCTION

his study investigated potential of the use of Drill Cuttings Ash (DCA) in the stabilisation of Niger Delta soils for road construction. Most of the in-situ soils encountered in the region are fine-grained and highly plastic that would require special treatment. Four soil samples were obtained and the following tests were carried out: classification, compaction, California Bearing Ratio (CBR), and Unconfined Compressive strength (UCS). Dry DCA quantities ranging 2 – 8 percentages by weight of the soil was added to the air-dried soils for the stabilisation process. They were classified as A-6 (clayey soil), A-2-6 (clayey sand), A-3 (silty fine sand), and A-4 (silty clay soil). Generically, the unstabilised soils were fine-grained having low to medium plasticity, with low shear strength. Other results showed that 6% DCA content caused improvement in the texture, plasticity, and dry density of the clayey soil, while its CBR and UCS parameters compared favourably well with the unstabilised soil values. Also, there was increase in CBR value of the clayey soil after soaking for 24 hours. DCA increased the plasticity of the clayey sand, silty fine sand, and silty clay soil, and there was no substantial improvement in their strength properties. These results showed that DCA would be useful in improving clayey soilswhich are known to be prone to excessive swelling and difficult to handle during construction especially after heavy rainfall.     &nbsp

Comparative Evaluation of Batch and Continuous Anaerobic Digesters in Biogas Production from Municipal Solid Waste using Mathematical Models

An investigation was conducted into the suitability of either of the batch or continuous (CSTR) digesters for anaerobic degradation of municipal solid waste (MSW) in the production of biogas. Mathematical models were developed for the design and evaluation of the two systems. The development of the models was based upon a material balance analysis of the digesters'operation. A Microsoft Visual Basic Version 6.0 Programme was developed for the solution ofthe model equations, and the digesters' operations simulated over a range of percentage total solids (PTS) concentration of 4-10% for the CSTR and 4-30% for the batch digester, and fractional conversion of 0.2-0.8. The results of the simulation show that although the amount of methane (0.0764m3) produced per unit volume of the batch digester is about 4 times less than the amount (0.284m3) per unit volume of the CSTR, the cost per unit volume of the batch digester ($5.98) is 6 times less than that of the CSTR ($33.8), suggesting that the overall cost of producing gas with the batch digester would be more economical. So, it was deduced that the batch digester is better suited for the digestion of MSW for biogas production, compared to the CST

Effect of Total Solids Concentration of Municipal Solid Waste on the Biogas Produced in an Anaerobic Continuous Digester

Municipal Solid Waste (MSW) contains a relatively large amount of organic matter, which decomposes by the actions of microorganisms under anaerobic conditions to produce biogas. The total solids (TS) concentration of the waste influences the pH, temperature and effectiveness of the microorganisms in the decomposition process. This work investigated various concentrations of the TS of MSW in an anaerobic continuously stirred tank reactor (CSTR) and the corresponding amounts of biogas produced, in order to determine conditions for optimum gas production. Five laboratory-scale anaerobic batch digesters of 5 litres volume each were set up for the digestion of 2kg of shredded MSW diluted to a %TS concentration of 26.7%. The results from the batch experimentation were adapted to the design of a CSTR for the digestion of MSW. The CSTR was simulated over a range of %TS concentration of 4-10, at a maximum fractional conversion of 0.8 to cater for system inefficiencies. Mathematical models were developed for the process and solved using the Microsoft Visual Basic version 6.0 Programme. The results show the amount of biogas produced as a power function of the %TS concentration, indicating that as the process continues, a time comes when any marginal increase in the %TS concentration would no longer contribute to the increasing volume of biogas produced. The results further show that, given the limiting upper boundary of the %TS concentration, optimum biogas production in a CSTR digesting MSW cannot be ascertained with the concentration of the %TS alone

Monitoring of microbial hydrocarbon remediation in the soil

Bioremediation of hydrocarbon pollutants is advantageous owing to the cost-effectiveness of the technology and the ubiquity of hydrocarbon-degrading microorganisms in the soil. Soil microbial diversity is affected by hydrocarbon perturbation, thus selective enrichment of hydrocarbon utilizers occurs. Hydrocarbons interact with the soil matrix and soil microorganisms determining the fate of the contaminants relative to their chemical nature and microbial degradative capabilities, respectively. Provided the polluted soil has requisite values for environmental factors that influence microbial activities and there are no inhibitors of microbial metabolism, there is a good chance that there will be a viable and active population of hydrocarbon-utilizing microorganisms in the soil. Microbial methods for monitoring bioremediation of hydrocarbons include chemical, biochemical and microbiological molecular indices that measure rates of microbial activities to show that in the end the target goal of pollutant reduction to a safe and permissible level has been achieved. Enumeration and characterization of hydrocarbon degraders, use of micro titer plate-based most probable number technique, community level physiological profiling, phospholipid fatty acid analysis, 16S rRNA- and other nucleic acid-based molecular fingerprinting techniques, metagenomics, microarray analysis, respirometry and gas chromatography are some of the methods employed in bio-monitoring of hydrocarbon remediation as presented in this review

Farm mechanization leading to more effective energy-utilizations for cassava and yam cultivations in Rivers State, Nigeria

Surveys have been conducted, under the auspices of the Ministry of Agriculture and Agricultural Development Projects (ADPs), in the 23 local-government areas of the Rivers State, Nigeria. A structured questionnaire, personal visits to farms and interactions with information repositories were used. The quantities of energy consumed by tractors used in activities associated with the growing of cassava and yam crops in those areas were compared with traditional operations, using just manual labour. Within the period of 1986–2004, the total energy utilizations in the production of these crops, in the 23 local government areas, were 2738.87 and 33.5 MJ for tractor-power and traditional-manual operations, respectively. The tractorization intensity (TI) dropped from 0.352 hp/ha in 1986 to 0.345 hp/ha in 2004. This result was below the presently advocated 0.5 hp/ha for agricultural operations in order to increase crop production. This study identified the causes of this shortfall and recommended, at least for the short- term future, that farm industrialization of all sectors should be subsidiz

Petroleum contaminated ground-water: Remediation using activated carbon.

Ground-water contamination resulting from the leakage of crude oil and refined petroleum products during extraction and processing operations is a serious and a growing environmental problem in Nigeria. Consequently, a study of the use of activated carbon (AC) in the clean up was undertaken with the aim of reducing the water contamination to a more acceptable level. In the experiments described, crude-oil contamination of ground water was simulated under laboratory conditions using ground-water samples collected from existing hand-dug wells at Eagle Island, Port Harcourt, Nigeria. Different masses of the absorbent (i.e., activated carbon) were then added to the samples of ground water. The so treated water samples were left to equilibrate for 7 days, after which the total petroleum hydrocarbon (TPH) contents of the samples were measured. Adsorption isotherms were derived for the two forms of activated carbon used, namely granular activated-carbon (GAC) and powdered activated-carbon (PAC). Results of the TPH analyses showed that activated carbon is an excellent means for the stripping-off of the contaminant: there were decreases in contaminant concentration from an initial concentration of 9304.70 mg/l to average final concentrations of 361.00 and 12.37 mg/l, that is, 96% and 99.9% resulting from the same amounts of GAC and PAC applications respectively. The results of this study revealed that the powdered form of AC would be very effective in the remediation of petroleum-hydrocarbon contaminated ground water and its use is therefore recommended

Bioremediation of a crude-oil polluted agricultural-soil at Port Harcourt, Nigeria.

A combination of treatments, consisting of the application of fertilizers and oxygen exposure, was evaluated in situ during a period of six weeks. Conditions of a major spill were simulated by sprinkling crude-oil on experimental cells containing agricultural soil. The remedial treatments were then applied and the soil characteristics analyzed after set periods. Soil physicochemical parameters, such as moisture content, pH value, electrical conductivity as well as organic-carbon and total-nitrogen contents, showed distinct variations with time. The total heterotrophic-bacteria (THB) count in all the treatment cells increased with time. The control cell, O (which was not treated) indicated no signs of remediation within the study period. The hydrocarbon losses (50–95%) experienced in the five other treatment-cells revealed the effectiveness in degrading the hydrocarbon contaminant. The results of this study indicate that the application of increased concentrations of nutrients (by the application of fertilizers) lead to greater rates of biodegradation of petroleum-polluted agricultural soils

Bio-remediation of a sludge containing hydrocarbons

Bio-augmentation has been used as a bio-remediation option for hydrocarbon-contaminated, oily-sludge restoration. This sludge was obtained from the Bonny-Terminal Improvement Project (BTIP) for Bonny Island, near Port Harcourt, Nigeria. Its total hydrocarbon-content (THC) was 69,372 mg/kg of sludge. Three treatment reactors (X, Y and Z) and one control reactor (A) were charged with 1500 g of oily sludge and 250 g of agricultural soil (i.e. an oily sludge to soil ratio of 6:1), the mixture homogenized and allowed to settle for seven days before various CFUs were added to reactors X, Y and Z. Reactor A did not receive any bio-preparation. The agricultural soil served both as a nutrient and a microbe carrier. With regularly scheduled mixing and watering, the THC reduction in the oily sludge varied between 40.7% and 53.2% within two weeks as well as between 63.7% and 84.5% within six weeks of applying the bio-remediation. The CFU counts of the added bio-preparation varied between 1.2 × 1212 and 3.0 × 1012 CFU/g of sludge and decreased to 7.0 × 1011 CFU/g of sludge by the end of the sixth week. The pH of the degrading sludge fluctuated between 6.5 and 7.8 during the same period. When compared with the performance of the indigenous microbes in the control sample, the added bio-preparation evidently increased the THC reduction rate in the oily sludge

STABILISATION OF NIGER DELTA FAT CLAY WITH BLEND OF BINDERS FOR SUBGRADE APPLICATION (PART 3) - TRIAL STABILISED ROAD SECTIONS IN SAMPOU, NIGER DELTA

The field performance of subgrade fat clay stabilised with additives and cement (PC) was evaluate by constructing trial sections along Odoni-Agbere road in Sampou, Bayelsa state. The blends mixed with the subgrade used in the study were, Drill Cuttings Ash (DCA)-PC (1:1), sand-PC (4:1), and lateralite-PC (2:1). Comparison of the dry density of cored stabilised samples with the laboratory samples showed that 100% compaction was achieved in the field for all the sections. Dynamic Cone Penetrometer (DCP) and field plate loading tests were used to determine the in-situ California Bearing Ratio (CBR) and settlement respectively. The in-situ CBR of the unstabilised and stabilised sections exceeded the targeted 15%. However, the in-situ CBR of the unstabilised section could be compromised if the soil is excessively manipulated and excess water is present. The percentage increase in settlement after two cyclic loading operations for the stabilised section ranging from -17 to 7%. This study revealed that the stability of the stabilised sections could be ensured if they are sealed on or before the 45th day after construction