The ionic character of a groundwater is defined by the following hypothetical combinations: Ca(HCO3)2 = 3.0 meq/L Mg(HCO3)2 = 0.4 meq/L NazSO4 = 0.2 meq/L MgSO4 = 0.8 meq/L NaCl = 0.6 meq/L %3D Draw a milliequivalents-per-liter bar graph. Is the hardness of this water considered excessive? What process do you recommend for precipitation softening of this water?

6. Identify the two species within the carbonate system that are the most relevant to the following situations, and identify the associated equilibrium constant: a. Dissolution of an Alka-Seltzer tablet (sodium bicarbonate, citric acid, aspirin) in water to create an effervescent pain-relieving drink. b. The effects of ocean acidification on the health of coral reefs.

1. The following information is provided for an activated sludge system design: Parameter Symbol Value Units Flow rate Q 10000 m³/d Influent BOD So 150 mg/L Effluent BOD S 2 mg/L Hydraulic residence time Ꮎ 4 hr Mean cell residence time Oc 6 d Maximum specific growth rate μm 3 1/d Half saturation constant Ks 40 mg/L Yield coefficient Y 0.5 Endogenous decay coefficient b 0.08 1/d Death rate coefficient γ 0.04 1/d Determine: a) The aeration tank biomass concentration (X) in mg/L b) The aeration tank oxygen requirement in kg/d c) The rate of biomass wasting in kg/d

The base of a river in in contact with the top of an aquifer. A truck carrying bags of powdered cyanide is on a bridge crossing the river when a large bump causes one of the bags to fall into the river. The water in the river suddenly becomes polluted by the cyanide with a concentrations of 6.78 mg/L. The aquifer has an average linear ground water velocity of 0.256 m/day. Laboratory analyses data indicates that longitudinal dispersivity can be found through the equation: a = 0.86(log Ls)² where Ls is the length of the straight line path between two points along the path of transport. Find the longitudinal dispersion 108 m downstream from the bridge. Assume that the cyanide solute has a diffusion coefficient of 3.6 x 10 -5 m²/s and the aquifer has a coefficient related to tortuosity (o) equal to 0.8. Find the coefficient of hydrodynamic dispersion.

When a pressure of 2×10^4 kN/m² is applied to 50 litres of a liquid, its volume is decreased by 0.5 litre. The bulk modulus of liquid in N/m² is