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BackgroundImproper waste disposal is responsible for the contamination of both surface and ground water resources. Heavy metals leached from improperly disposed solid waste constitute grave environmental and health hazards because of their toxic and persistent nature. There are thousands of open dumps in Nigeria one of which is the Enugu State Waste Management Authority dumpsite.MethodForty sampling nodes were systematically established around the Enugu State waste Management Authority central dumpsite located at Ugwuaji, Enugu State, Nigeria. Ten heavy metals (arsenic, cadmium, cobalt, copper, chromium, iron, lead, manganese, nickel and zinc) were sampled at different depths of each node in both rainy and dry seasons.ResultIron and lead were the predominant metals in the vicinity of the waste dump with average values of 132.10 mg/kg and 117.52 mg/kg respectively. The order of abundance of the ten heavy metals monitored is Pb > Fe > As > Zn > Cu > Co > Ni > Cd > Cr > Mn. Generally, there was significant correlation (0.25 to 0.74) among all the metals except between cobalt and manganese in the rainy season. In the dry season, all the metals were significantly correlated (0.29 to 0.813) except for copper and lead, copper and arsenic, zinc and arsenic, and cobalt and manganese. The concentrations of most of the heavy metals approached a constant level at a depth of 1 m. On the other hand, the concentrations of arsenic, cobalt and iron continued to decrease even at a depth of 2 m. The pollution loading index values for the soil are 1.706 for rainy season and 2.54 for dry season.ConclusionThe high pollution loading index represents a significant level of deterioration. It can be concluded that the dumpsite constitute a serious environmental and health hazard.

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/ In the search for a cheaper material to effectively condition sludge, oil-free moringa seed was prepared and tested. A Soxhlet apparatus was used to extract the oil from moringa seed (Moringa oteifera). The oil-free seed (marc) has been found to have higher conditioning potential than the ordinary moringa seed. However, the traditional ferric chloride is still a better sludge conditioner than moringa seed marc. For the digested domestic sludge used, optimum conditioning dosages were found to be 0.6, 0.80, and 1.10% of the total solids for ferric chloride, marc of the moringa seed, and ordinary moringa seed, respectively. Since little or no operational material is lost in the extraction process, the moringa seed marc is a promising conditioner in place of the ordinary seed.

This study modeled the relationship between Sludge Filtration Resistance (SFR) and Capillary Suction Time (CST) using the data generated from different concentrations of CaCl 2 for SFR and CST empirically using the Equation proposed by Christensen et al. (1993). The main purpose of conducting CST and SRF tests at wastewater treatment plants is to save operating costs by evaluating the optimal dose of the sludge conditioner, known as the dose of coagulant that yields the minimal capillary suction time or resistance to filtration. In order to establish a relationship between the SFR with CST, there is a relatively good correlation between CST and SFR. The results showed that the values of CST decreased with increasing CaCl 2 concentration, and a good dewaterability could be obtained at the CaCl 2 dosage of 18 g with the corresponding CST of 5.52 s for 20 mm internal cylinder and 30.84 s for 14.5 mm internal cylinder. The results of SFR tests shown decreased with an increase in CaCl 2 dosage. The optimal CaCl 2 dosage was 18 g and the corresponding SFR was 2.65 × 10 8 N•s/m 5. The results of this study for CST recommend larger diameter cylinder to be used to test heavy sludge because the larger cylinder significantly reduces the variability and the time taken to conduct the CST tests.

Sludge generated during wastewater treatment is difficult to handle due to their high water content, hence a need for dewatering. The factors that affect the outcome of capillary suction time (CST) were studied using piggery and domestic sludge samples conditioned with ferric chloride. Effects of conditioner concentration, hydrostatic pressure and mixing time were investigated. Filtrate flow rate studies were also carried out as an alternative to wet front progression to determine CST. Ferric chloride was varied from 0.002 to 0.008 g/ml, hydrostatic height was varied from 20 to 40 mm while mixing time ranged from 0 to 120 sec. The optimum conditioner concentration was observed to be 0.0055 and 0.0035 g/ml for piggery sludge and domestic sludge respectively. At 5 % level of significance, hydrostatic height was observed to have no significant effect on the CST for the range of hydrostatic heights chosen. The optimum mixing time observed for 90 g/l and 30 g/l piggery sludge was 50 and 25 sec respectively. While the optimum mixing time for 28 g/l and 14 g/l domestic sludge was 10 and 5 sec respectively. Flow rate was discovered to have an inverse relationship with CST, with the optimum conditioner concentration corresponding to the peak flow rate and minimum CST for both test samples. Hence, in other to eliminate the difficulty presented by the anisotropic property of the capillary suction apparatus (CSA) filter paper, filtrate flow method can be used instead of wet front progression method.

An equation for sludge dewatering using FMTL An equation for sludge dewatering using FMTL An equation for sludge dewatering using FMTL An equation for sludge dewatering using FMTL plant made of 12mm plant made of 12mm plant made of 12mm plant made of 12mm thick thick thick thick steel plate was used in designing a drying steel plate was used in designing a drying steel plate was used in designing a drying steel plate was used in designing a drying a total area of 0.90m a total area of 0.90m a total area of 0.90m a total area of 0.90m 2 2 2 2 and was used in dewatering sewage sludge from t and was used in dewatering sewage sludge from t and was used in dewatering sewage sludge from t and was used in dewatering sewage sludge from t water water water water treatment plant. Parameters affecting filtration pr treatment plant. Parameters affecting filtration pr treatment plant. Parameters affecting filtration pr treatment plant. Parameters affecting filtration pr analysis approach. The derived equation based on the concept of specific resistance analysis approach. The derived equation based on the concept of specific resistance analysis approach. The derived equation based on the concept of specific resistance analysis approach. The derived equation based on the concept of specific resistance performance o performance o performance o performance of the sand drying bed as a slud f the sand drying bed as a slud f the sand drying bed as a slud f the sand drying bed as a slud obtained from the sewage plant, the theoretical prediction of the derived equation gave a close relationship to the obtained from the sewage plant, the theoretical prediction of the derived equation gave a close relationship to the obtained from the sewage plant, the theoretical prediction of the derived equation gave a close relationship to the obtained from the sewage plant, the theoretical prediction of the derived equation gave a close relationship to the practical values with a correlation of 0.994 practical values with a correlation of 0.994 practical values with a correlation of 0.994

In this study, a model for sludge filtration resistance (SFR) was developed using electrical resistance analogy by relating the rate at which water flows to the current of charge to determine Sludge Filtration Resistance using a typical single Electrical Resistance from a Direct Current Circuit. Synthetic sludge was successfully formulated for experimental purposes. The advantage of using synthetic sludge was that they permitted experiments to be performed on stable samples with known physical and chemical properties not subject to degradation by microbial activity. The result from the present study indicates the effect of conditioner on synthetic sludge filtration at variable pressure for sludge filtration resistance (SFR) and the trends in the results indicated that SFR reduces with increase in the concentration of dissolved salt (CaCl 2 ). The linearity observed between plot of volume of filtrate versus time of filtration by correlation coefficient of R 2 = 0.9292 (Figure 1) for 10 g of CaCl 2 and R 2 = 0.9294 (Figure 2) for 18 g of CaCl 2 . It is evident from the calculated values that they are very strong and have testified that the effect of conditioner on synthetic sludge filtration at variable pressure for sludge filtration resistance (SFR) using electrical resistance analogy is very satisfactory. When compared the existing data from SFR with other measure of filterability calculated using Carman's equation to validate the model, it was observed that specific resistance decreases as the concentration of CaCl 2 (dissolved salt) increases which agrees with SFR.