Ozone dissolution system design is important for meeting transfer efficiency (TE) goals. Large sidestream pump flow (L) and high venturi inlet pressure improves TE but increases operating cost. Ozone TE was examined at a 25 gpm (97-Lpm) pilot-scale sidestream system with (SS w-dg ) and without (SS wo-dg ) degas separation. Under constant ozone dose conditions, process operating parameters were varied including sidestream gas/liquid (G/L) ratio, venturi-inlet water pressure, venturi-outlet water pressure, feed gas pressure, and ozone gas concentration. Performance results included determination of TE, ozone exposure (CT HDT ), and hydraulic detention time (T HDT ). Several design aspects of sidestream ozone systems were examined to improve mass transfer by using remixing devices, protecting ozone gas piping from corrosion, calculating sidestream ozone residual, and driving force for mass transfer. Moisture contamination of ozone supply lines may cause corrosion and/or decomposition of ozone gas that releases heat and destroys ozone. Ozone gas piping design is critical to prevent trapping water that might enter gas pipe during power outage or when units are offline. During plant operation below design flow, multiple constant speed pumps or variable speed pumps were evaluated to reduce overall operating costs.
ARTICLE HISTORY
Purpose -The purpose of this paper is to explore the demand and supply relationship between urban and non-urban land, the latter's diminishing supply, arguments for and against its preservation, methods in which preservation might be achieved and one method in particular, with which the authors have considerable experience, that involves the purchase of development rights and density credits. Design/methodology/approach -The research design involved meetings with farmers, city and county officials and members of several land conservation organizations, bringing together several hundred agricultural and residential real estate transactions, quantitative analysis of the transaction data using descriptive and hedonic methods, developing property attribute values and thereby determining the value of agricultural development rights and urban density credits. Findings -Agricultural development rights were valued, on average, at $9,000 per acre. Commercial development rights were valued, on average, at $9.00 per square foot of floor area (FAR). Practical implications -By acquiring agricultural development rights the process of agricultural land being converted to urban purposes can be slowed or halted. Valuing and selling development rights is a straightforward means of permitting urban density that is understood by developers and easily, objectively and transparently quantified. It is also a good method of raising funds for the acquisition of agricultural development rights. Originality/value -The valuation process developed and employed does away with the need for individual appraisals of rights to be acquired and sold. Therefore this is a very efficient process. Also, it shows how farmers, preservationists and planners can be brought together to solve a common problem.
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