Effects of water hardness on selective flocculation of diasporic bauxite

The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2＋ and Mg2＋ in hard water. The results indicated that, not only the concentration of electrolyte ions but also the ionic valence of the electrolyte ions affects the settling behavior of kaolinite; hard water significantly affects its selective flocculation owing to Ca2＋ and Mg2＋; general dispersants could not eliminate the effects of Ca2＋ and Mg2＋. Self-made softening agent in our lab could weaken or eliminate the effects of hard water on flocculation processes. The results of molecular dynamics simulation show that softening agent molecules could restrict Ca2＋ and prevent them from playing their roles, so as to eliminate the effects. The continuous pilot experiment results of bauxite flocculation were even better than those obtained in laboratory.

Effect of Water Hardness on the Toxicity of Cobalt and Nickel to a Freshwater Fish,Capoeta fusca

Objective To determine the effects of water hardness on the toxicities of cobalt （Co） and nickel （Ni） to a freshwater fish, Capoetafusca. Methods Toxicity was investigated by static bioassay. Fish were exposed to cobalt （as COCI2） and nickel （as NiCI2） for 96 h in waters with two levels of hardness （＂hard＂ and ＂very hard＂, nominally 130 mg/L and 350 mg/L as CaCO3, respectively）. Results Water hardness had a significant effect on the acute toxicity of both elements. The 96 h LC50 values for Co were 91.7 mg/L and 204.8 mg/L in hard and very hard waters, respectively, and for Ni the 96 h LC50 values were 78.0 mg/L and 127.2 mg/L, respectively. Conclusion The fish were more sensitive to Co and Ni toxicity in hard water than in very hard water; very hard water protects C. fusca against the toxicity of Co and Ni.

Urban Services Delivery in Limbo： A Provisional Assessment of Gweru＇s Water Supply System

This study sought to assess Gweru＇s water supply system from the source to the consumer to find out whether the water is safe for domestic purposes, mainly consumption. Water samples were taken from Gwenoro dam （raw water）, Gwenoro treatment plant （treated water） as well as from GIS-generated random points of residential areas closest to Gwenoro and furthest from both the dam and the treatment plant. These were taken for laboratory testing where parameters like pH, hardness, turbidity and DO （dissolved oxygen） were tested. Questionnaires were used to solicit the views of the consumers on water quality and water service delivery from eight randomly selected residential suburbs. Interviews were also administered to Gwenoro Water Treatment Plant superintendent and deputy to get insight into the day to day challenges that they have to grapple with. Results generally show that treated water from Gwenoro treatment plant is relatively safe to drink for those who have access to it. However, some consumer points like Mkoba 13 and Mkoba 18 receive water whose DO is out of the recommended range. Suburbs which lie on higher ground like Mkoba 19 and Mkoba 14 however rarely receive water from Gwenoro with some residents of Mkoba 19 having had no water from their taps for more than three years now. The study recommends that new equipment be bought for the treatment plant so that treated water reaches all parts of the city. Newly resettled farmers in the Upper Runde Catchment must be resettled elsewhere while urban stream bank cultivation must be banned to reduce water pollution as well as possible sedimentation of Gwenoro dam.

Proximal Femoral Cortical Thickness and Medullary Canal Diameter in Soft and Hard Water Regions

This study compared proximal femoral morphology in patients living in soft and hard water regions. The proximal femoral morphology of two groups of 70 patients living in hard and soft water regions with a mean age of 72.29 (range: 50 to 87 years) was measured using an antero-posterior radiograph of the non-operated hip with magnification adjusted. The medullary canal diameter at the level of the lesser trochanter (LT) was significantly wider in patients living in the hard water region (mean width: 1.9 mm wider;p = 0.003). No statistical significant difference was found in the medullary canal width at 10 cm below the level of LT, Dorr index, or Canal Bone Ratio (CBR). In conclusion, the proximal femoral morphology does differ in patients living in soft and hard water areas. These results may have an important clinical bearing in patients undergoing total hip replacement surgery. Further research is needed to determine whether implant survivorship is affected in patients living in hard and soft water regions.

Comparative Evaluation of Calcium, Magnesium, Copper and Zinc Removal by Wood Ash, Sodium Carbonate and Sodium Hydrogen Phosphate

Remediation via adsorption process has been proven to be one of the best water treatment technologies globally. Many adsorbents, including agricultural wastes, have been considered for the removal of a variety of pollutants from water. However, most of the studies reported in the literature used metal concentrations below 1000 ppm. It is also known that initial metal concentrations in polluted aqueous solutions, as well as metal and adsorbent type, are some of the factors that affect metal removal. Therefore, this project examined the remediation of water contaminated by 1000 ppm of lead, zinc, copper, magnesium, and calcium ions using wood ash, sodium hydrogen phosphate (dibasic), and sodium carbonate (dibasic). Comparative analysis of the results showed the order of order of metal removal by the adsorbents as: dibasic phosphate (Ca > Cu > Pb > Zn > Mg);dibasic Carbonate (Pb ~ Ca > Zn > Cu > Mg);Wood ash (Mg > Cu > Zn > Pb > Ca). These results suggest that metal and adsorbent type as well as the inherent chemical properties of these metal cations may contribute to the varying binding affinity of the metals to the adsorbent ligand(s) and thus, affect the extent of metal removal. It is equally worthy to note that wood ash more effectively removed hardness metals (Mg and Ca) from water than the inorganic phosphate and carbonate ions.

The use of graphene oxide membranes for the softening of hard water

Strong chemical interactions between the oxygen-containing functional groups on graphene oxide(GO)sheets and the ions of divalent metals were exploited for the softening of hard water.GO membranes were prepared and evaluated for their ability to absorb Ca2+and Mg2+ions.These GO membranes can effectively absorb Ca2+ions from hard water;a 1 mg GO membrane can remove as much as 0.05 mg Ca2+ions.These GO membranes can be regenerated and used repeatedly.