Interaction between suspended and settled solid particles in cassava wastewater

Cassava (Manihot Esculenta, Crantz) is a very important staple food in most developing countries. During its processing into cassava flour or garri, wastewaters are generated and are indiscriminately discharged into the public sewers or into the environment and in some cases; the fermented wastewater is usually poured into latrines with the aim of degrading sewage. This study is aimed at finding out the interaction between the suspended solids and settled solids of cassava wastewater. Cassava wastewater was collected from a cassava processing plant at Ogige main market in Nsukka town and monitored for 14 days. Half of the samples collected were left unstirred and the other halves were continuously stirred. The parameters monitored include biochemical oxygen demand (BOD5), suspended solids, coliform, cyanide and pH. Results showed that there was a 73.4, 27.5 and 99.9% reduction in the settled solids for BOD5, suspended solids and coliform bacteria respectively, for the stirred samples while there was a 97.8, 44 and 99.9% reduction in the settled solids for BOD5, suspended solids and coliform bacteria respectively, for the unstirred samples. Overall, the unstirred samples performed better than the stirred samples with respect to BOD5 and SS removal. The result of this work will guide sanitary engineers in the selection of influent parameters for the effective design of treatment units

Selection of Biosorbents for Biosorption of Three Heavy Metals in a Flow-Batch Reactor Using Removal Efficiency as Parameter

Within the last three decades, the use of low cost biosorbents like bacteria, fungi, algae and some agricultural by-products have been investigated for their biosorption capacities. In this paper, the biosorptions of three heavy metals (zinc, copper and manganese) from aqueous wastewater solution by five microorganisms (Bacillus circulans, Pseudomonas aeruginosa, Staphylococcus xylosus, Streptomyces rimosus and Saccharomyces sp.(Yeast) were investigated using a combined flow and batch processes. The biosorbents were air-dried without subjecting them to oven heat. Factors affecting biosorption capacity also known as metal uptake capacity, such as solution pH, initial ion concentration of heavy metals, mass of biosorbent and contact time were investigated. The removal efficiencies of the individual microbes were also calculated. The maximum biosorption capacities for the three heavy metals occurred at pH between 5.5 to 6.5. The biosorption of zinc ion by Staphylococcus xylosus yielded the highest removal efficiency of 94%. Also, the biosorption of copper and managense ions by Bacillus circulans produced highest removal efficiencies of 97% and 90% respectively. Initial ion concentrations of heavy metals and mass of biosorbents increase with biosorption capacity. Furthermore, Langmuir isotherm better described equilibrium biosorption of copper by Pseudomonas aeruginosa, Staphylococcus xylosus and Saccharomyces sp. (Yeast) with linear regression coefficient of correlation, R2 of 0.8646, 0.9820 and 0.9902, Freudlinch isotherm better described the biosorption of copper by Bacillus circulans and Streptomyces rimosus with linear regression coefficient of correlation of 0.7233 and 0.9290 respectively. Lastly, Langmuir isotherm better described the biosorption of manganese by Pseudomonas aeruginosa and Streptomyces rimosus with linear regression coefficient of correlation, R2 of 0.9394 and 0.9880 respectively. On the other hand, Freudlinc isotherm better described the biosorption of Manganese by Bacillus circulans, Staphylococcus xylosus and Saccharomyces sp (Yeast) with linear regression coefficient of correlation, R2 of 0.7891, 0.9753 and 0.7915 respectively.http://dx.doi.org/10.4314/njt.v34i2.2

Asphaltic Concrete Pavement Strength and the Impact of Rainfall

Studies have shown that moisture impacts on the strength of flexible pavement surface of asphaltic concrete. Several investigations and relevant researches treated the effect of subsurface and surface water sources, on the durability of flexible pavements. This study is focused on the surface water sources, as a result of precipitation (rainfall), on the surface of flexible pavements. To conduct this experiment, the considerations made include (i) the continuous exposure of the pavement surface to annual rainfall (ii) application of pavement exposure to moisture in the field. This study considered the amount of rainfall each day, as the duration (age) of pavement exposure to moisture (being under water during rainfall). For the purpose of this experiment, the Owerri to Onitsha about 90km of dual carriage way in south east of Nigeria, was considered. This is a flexible pavement that traverses through the rain forest belt, characterized with high amount of annual rainfall values. Flexible pavement specimens from this road were obtained, cleaned and immersed in water after weighing, to keep vital records of the necessary parameters, before further tests at 7days intervals. Values of strength obtained after days in water, that approximated to the appropriate field situation of exposure to rainfall, showed a consistent loss of strength, from the crushing strength results

CLASSICAL OPTIMIZATION OF BAGASSE ASH CONTENT IN CEMENT-STABILIZED LATERITIC SOIL

Optimization of construction materials with laboratory data is a very possible way of minimizing waste of resources (materials and cost). There had been several successful attempts of optimization of construction materials. However, optimization in soil stabilization for road-work has been very rare because of its complexities. Compaction, California bearing ratio, unconfined compressive strength and durability tests were carried out on cement-stabilized soil. Constant cement contents of 2%, 4%, 6% and 8% with variations of bagasse ash from 0% to 20% at 2% intervals and all percentages used were by the weight of dry soil.  The classical method was applied in this work to optimize the amount of bagasse ash content in cement-stabilized lateritic soil. Geometric models that govern the relationships of cost of bagasse ash content, cement content, optimum moisture content and strength characteristics of the stabilized-soil matrix were used to develop non-linear programming model. Then it was linearized and solved using the simplex method with sensitivity analysis. The optimal solution at the desired unconfined compressive strength and California bearing ratio for sub-base of road-work for bagasse ash content, cement content and optimum moisture content were found to be 14.03%, 4.52% and 22.46% respectively. Optimzation and the use of bagasse ash gave a cost benefit of 9.24% with a better mix. The classical optimization technique appears to be suitable in soil stabilization. http://dx.doi.org/10.4314/njt.v35i3.

Technical Note: Geotechnical Examination of the Geophysical Properties of Olokoro Borrow Site Lateritic Soil for Road Works

This present work was carried out to determine the geotechnical properties of Olokoro lateritic soil. Tests were carried out on the sample soil which includes the Atterberg limit tests, particle size distribution analysis; sedimentation test, compaction test using the West African standard and California Bearing Ratio (CBR) test as specied by the Nigerian General specication (1997). The liquid limit, plastic limit and plasticity index were found to fall into A-2-7 soil of AASTO classication and SP group of Unied Classication. The compaction characteristics of the soil were found to be 1.90mg/m3 and 14.76% for maximum dry density and optimum moisture content respectively on West African Standard. The CBR value was found to be 26%. It was recommended that the soil is good as a lling material in road subgrade and other construction works and require modication to improve its properties for sub-base and road base material.Keywords: olokoro lateritic soil, particle size distribution, compaction test, geophysical properties, california bearing rati

Assessment of Pollution-Induced Dissolved Oxygen Variation in River Challawa

The study is aimed at investigating the effect of industrial effluents on the water quality of River Challawa. Chemical analyses of samples of the river water collected at predetermined sampling points along a 10.644 km stretch were undertaken and the observations were subjected to ANOVA and regression analyses.The results obtained indicated that the DO values ranged from 2.4 mg/l to 1.9 mg/l, while the BOD5 ranged from 443 mg/l to 1654 mg/l; the COD ranged from 1296 mg/l to 4565 mg/l. The self-purification factor (f) for the River Challawa varies between 0.40 per day and 0.56 per day which puts the river in the sluggish stream category and as a heavily polluted stream. The predictions indicated significant relationship with the observed values at 95% level of significance.http://dx.doi.org/10.4314/njt.v34i3.2

Modeling of Evaporation Losses in Sewage Sludge Drying Bed

A model for evaporation losses in sewage sludge drying bed was derived from first principles. This model was developed based on the reasoning that the rate at which evaporation is taking place is directly proportional to the instantaneous quantity of water in the sludge. The aim of this work was to develop a model to assist in the design of drying beds for effective treatment of wastes derived from households’ septic systems.  Data generated after evaporation experiment in sewage sludge drying bed over a period of 15 days at 24 hours intervals was used for the modeling. The model was calibrated and regressed using data for days 1 to 8 by employing the Pearson’s correlation coefficient, “ ” was found to be -0.96124, after which verification was done and regressed using data for days 9 to 15 and  was found to be 0.9969 that these fits validates the model. Materials balance show that evaporation reduces with increase in seepage losses which can be enhanced with use of conditioners and coarser sands because of their larger pore spaces. It was discovered that evaporation from the sludge follows first order kinetic in agreement with the fundamental concept. The model will help in the prediction of total water losses due to evaporation over a given period which would aid in the design of drying beds.http://dx.doi.org/10.4314/njt.v34i4.3

Inventory Management in Delta Allied Wire Industries Limited Asaba

A good inventory system reduces production cost and consequently increases profit. Optimum management of inventory in the Delta – Allied Wire Industries Limited was studied in this research. The information needed was obtained through questionnaire and interviews of key staff of the company. Data collated were recorded for the operational 5 years period (1997 – 2001) under review and customers’ handling processes equally studied for improvement. The data collated were collated were analyzed using the Economic Order Quantity (EOQ) model under constant demand, non-instantaneous receipt as well as other possible scenarios. Results showed that if the order had been reduced from 12 per year to 2 or at most 5 per year savings of ₦602, 876 to ₦2,977,253 could have been made under constant demand. In addition, the company will have even greater saving if it encourages customers to purchase directly from the company than through the warehouses, thereby reducing the carrying cost. Recommendations based on the findings were made to the company for inclusion in future financial management planning and control

A Comparative Analysis of the Rebound Hammer and Ultrasonic Pulse Velocity in Testing Concrete

This work presents a study on the comparison between some non-destructive testing tech-niques (Rebound Hammer and Ultrasonic Pulse Velocity). Tests were performed to com-pare the accuracy between the rebound hammer and the ultrasonic pulse velocity methodin estimating the strength of concrete. Eighty samples (cubes of 150 x 150 x 150) wereprepared using two mix designs of 1:2:4 and 1:3:6 with a constant w=c ratio of 0.45 andwere tested at 7, 14, 21 and 28 days. The slump test was between 62 - 78mm. The resultsobtained from the non-destructive testing methods were correlated with the compressivestrength results which showed that a higher correlation existed between the Rebound Ham-mer and the compressive strength than the Ultrasonic Pulse Velocity. The rebound ham-mer readings had a correlation coecient of 0.794 while the ultrasonic pulse velocity hada correlation coecient of 0.790 for the 1:2:4 mix and the rebound hammer readings for1:3:6 was 0.783 and that for the ultrasonic pulse velocity was 0.777. Statistical analysisof the results obtained showed that there was no signicant dierence between the meansof the two methods for both mix at a 0.05 level of signicance

Analysis of the Environmental and Socio-Economic Impact of Noise Pollution in Eleme Petrochemical Company Limited

The impact of noise on the staff of Eleme Petrochemical Company Limited (EPCL), third parties, and resident/host communities was studied. Data collection involved physical identification of noise sources and spot reading of noise levels at 1.0m from source. The spatial measurements along the selected routes and estimate of dispersion rates were carried out. About one hundred and eight (108) noise sources were identified and subsequently grouped in terms of equipment types as: air cooler/fans (47%), pumps (37%), compressors (6%, and office areas and others (10%). In spatial variation of noise level measurements, eight (8) routes were identified numbering A Hand a total of 6.32 kilometers of distance and 523 point locations were covered. The measurements were taken at 25 meters interval for a period of four days. In addition to noise level measurements for equipment (noise sources), spot readings were equally taken at the office buildings and other designated areas. Also, questionnaires were administered to 100 workers whose daily activities expose them to different levels of noise at different durations. Results showed that the exposure of workers to noise levels were high to very high in all the areas apart from the office areas. Also, several of the workers suffer from various noise-induced sicknesses and their levels of productivity have been reduced by 31.4% on the average. Urgent measures for curtailment of noise and ultimate protection of the worker's health were presented. Low use of the available earmuffs showed the need to educate all categories of EPCL staff on the dangers of noise pollution