A prototype green roof was constructed and monitored in Pittsburgh, Pennsylvania, to demonstrate a way to reduce storm water runoff and combined sewer overflow (CSO) events. The large impervious surface area created by urban development in Pittsburgh creates a wet weather flow that the existing combined waste waster and storm water sewer system cannot contend with. Green or vegetated roofs can reduce the amount of storm water that reaches the sewer conveyance system by replacing an otherwise impervious roof with porous soil that retains rainwater and plants that evapotranspire resulting in reduced storm water flows to the sewer system. The prototype green roof reduced the runoff volume by up to 70% compared to a conventionally ballasted roof covering a control portion of the same building. A reduction of at least 20% was found for rainfalls of 1.5 cm (0.60 inches) or less. The green roof also reduced the flow rate of runoff throughout storms. Peak values from the green roof were between 5% and 70% lower than control roof flow rates. For some small storms, the time of peak flow rate was delayed by up to several hours. In general, the green roof delayed the start of runoff and extended the time period of low residual flows that existed at the end of a storm. Water quality tests indicate that in most cases for the storms observed, a first-flush phenomenon was not evident in green roof runoff samples. Levels of phosphorus and chemical oxygen demand (COD) were elevated by the green roof. Both the control and green roofs produced runoff that demonstrated neutralization of slightly acidic rainfall.

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:A technique for the removal and recycling of hexavalent chromium from electroplating industries was developed. It involves a two-phase process which consists of (1) the use of an activated carbon bed for the accumulation of chromium onto the surface of activated carbon followed by (2) the regeneration of the carbon leading to a concentrated chromium solution with potential for reclamation or reuse within the plating operation. Results from continuous ýow experiments showed that in excess of 99% chromium removal efficiency can be achieved. It was also revealed that regeneration of the exhausted carbon under acidic conditions recovered chromium in the trivalent state with concentrations as high as 3 g dm~3, more than 12 times the inýuent concentration. The adsorption capacity of the activated carbon was found to increase with successive cycles of adsorption/regeneration. However, when regeneration was achieved under alkaline conditions, the chromium was recovered in the hexavalent state with concentrations as high as 8·4 g dm~3, in excess of 33 times the chromium inýu-ent concentration. In addition, under caustic regeneration conditions, the data showed that the adsorption capacity in this case decreases with the increased number of exhaustion cycles. Mass balance calculation for both acid and caustic regeneration indicated that in both cases the regeneration process was incomplete with a recovery efficiency averaging around 50%. In an attempt to maximise the recovery efficiency, a combination of caustic followed by acid regeneration was applied to the exhausted activated carbon and the results led to a drastic improvement in the total recovery process (85-98%). These results clearly show that activated carbon is a viable candidate for the removal and recovery of chromium from electroplating industries. The critical advantage in the use of activated carbon is (1) the ability to regenerate and thus prepare a concentrated chromium solution for potential reclamation or recycle to the plating operation, and (2) the potential of avoiding the generation of hazardous sludge for land disposal.

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