The batch removal of arsenic from aqueous solution using low-cost adsorbent (powdered eggshell) under the influences of initial arsenic ion concentrations (0.50 to 1.50 mg/L), pH (3.2 to 11.5) and particle size of eggshells (63 to 150 µm) were investigated. Eggshells were collected from Obafemi Awolowo University, Ile-Ife, washed with distilled water, air dried, ground into powder and sieved into different sieve sizes using British standard sieve. Powdered eggshells were stored in a desiccator for use. Adsorption isotherms and dynamics of arsenic onto PES were studied. The study revealed that there was a slight reduction in the rate of adsorption of arsenic ion onto the larger particle size, but adsorption capacity and parameters were unaffected. Powdered eggshell with particle size of 63 µm removed up to 99.6% of the 1.5 mg/L of arsenic ion in synthetic water within the first 6 hours but decreased to 98.4% and 97.4% when the powdered eggshell particle sizes were increased to 75 and 150 µm respectively. The pH optimum for arsenic removal was 7.2. The adsorption isotherms and adsorption dynamic kinetic studied through the use of graphical method revealed that Freundlich, activated sludge adsorption and pseudo second-order kinetic models correlate significantly Abbreviations q e the adsorption capacity at equilibrium (mg/g) q t the adsorption capacity at time t (mg/g), k i the rate constant of pseudo first-order adsorption. k 2 the rate constant of pseudo second-order adsorption. α the initial adsorption rate β the desorption constant during any one experiment. R the per cent pollutant adsorbed (%) t the contact time (h) a the gradient of linear plots a L the Langmuir adsorption constant k id the intraparticle diffusion rate constant (/h) C 0 initial concentration of arsenic in the solution (mg/l) C e experimental concentration in the solution at equilibrium (mg/l) C t experimental concentration in the solution at time t (mg/l) X adsorbed concentration (mg/l) M mass of the adsorbent added (g) N constants related to equilibrium concentration of the solute a L constant related to adsorbent and adsorbate b L constants related to adsorbent only V volume of the sample used (300 ml) = 0.3 L K f Freundlich constant (l/g) K m constant for activated sludge model t (l/g) N m exponential constant for activated sludge model (mg/g) 74 Adsorption (2008) 14: 73-83

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Environmental pollution in Nigeria presents an urgent need to assess wastewater treatment facilities in various industries. This article presents an assessment of dissolved air flotation (DAF) operation in a dairy industry. The industry was visited, wastewater treatment facilities were assessed (based only on efficacy to remove selected environmental health-related pollutants) and measurements of essential design and characterization parameters were taken. The study revealed that the averages of flow rate, biochemical oxygen demand at 5 days (BOD 5 ), chemical oxygen demand (COD), suspended solids (SS) and total solids (TS) of the influent wastewater into the plant (DAF) were 3.45 L/s, 1652.37, 3304.67, 2333.82, and 4396.10 mg/L compared to effluent quality of 560. 37, 1127.33, 172.33, and 1866.67 mg/L for BOD 5 , COD, SS, and TS, respectively. The pH of the wastewater is being adjusted by addition of lime before the effluent equalization tank and individual efficacies of the system were 66. 09, 65.89, 65.89, 57.54, 8.68, and 94.49% for BOD 5 , COD, SS, TS, DS, and total nitrogen, respectively, with overall efficacy of 38.10%. It was concluded that failure (lower overall efficacy) of the system can be attributed to setting of lime in the oversized equalization tank (50 m 3 instead of 16.82 m 3 per 8 h shift), the lack of application of standardized engineering code and practices (provision of underground tank in the process, lack of complete coagulation processes, coagulation and flocculation units), lack of adequate aeration unit and lack of reliable systems for automatically adjusting dosage of coagulant and flocculant. Although, DAF unit is the centerpiece of a DAF-based system design, there are several other supporting systems important to optimal DAF operation. These observations, coupled with the analysis in this report, demonstrate that the facilities necessary to minimize continuous environmental pollution are lacking. Pollution will become an increasing problem unless pollution preventing codes and standards are developed; incorporated into government regulations and the regulations are enforced.

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This paper assesses the causes and socioeconomic impact of some recent cases of collapsed buildings in Nigeria. Information on selected collapsed buildings was collated, and a case study of a failed one-story building is presented for emphasis. A summary of the technical assessment and remediation of the building was presented as well. Both field and laboratory work involved close inspection of the building, excavation to reveal the condition of the foundation, taking samples of slabs and beams from the collapsed building for laboratory study, detailed structural analysis, a design analysis of the structural elements of the building to reveal causes of failure, and identification of remedial options and recommendation. Solubility of concrete in acids was used to assess the quality of concrete used. This study revealed that a lot of lives and properties have been lost in the various collapsed buildings, and these losses have negatively impacted the socioeconomic status of Nigerians. The results of the case study revealed that the main structural components (slab, beam, column, and footing) of the building were not properly proportioned and were seriously underreinforced, which led to excessive deflection. Additionally, concrete mixes used in the construction were found to be weak, and walls that should have been non-load-bearing ended up carrying loads and induced a hogging moment onto the slab for which reinforcement was not provided. The solubility tests showed that the ratio of calcium concentration of concrete mix used in the collapsed building to that of standard 1:2:4 concrete mixes were 0.03, 0.20, and 0.73, respectively. These low ratios indicate that the cement portion in the concrete was not adequate, and it was concluded that the concrete samples from the collapsed building contained less calcium than necessary for structural success. The summary of the assessment underscored the need for ensuring quality control and proper supervision in the construction of reinforced concrete structures.