Combined permeable pavement and ground source heat pump systems to treat urban runoff

BACKGROUND: This paper assesses the functioning of the next generation of permeable pavement systems. The overall concept is to combine traditional permeable pavement systems with ground source heat pump systems. Long-term research to provide data concerning nutrient reductions and microbial activity within experimental pavement rigs is required. RESULTS: The variability of temperature allowed for the survival of pathogenic organisms within the sub-base of permeable pavement systems. Counts of microbes and nutrient concentrations have been determined by direct observation (plate count tests) and chemical analysis, respectively. An analysis using numerical methods indicated 99% and 95% biochemical oxygen demand and ammonia-nitrogen removal, respectively. Supplementary carbon dioxide monitoring indicated relatively high microbial activity on geotextiles and within the lower parts of the sub-base. Low oxygen concentrations were measured in the space around the geotextile, where carbon dioxide concentrations reached 2000 ppm. CONCLUSIONS: The research enables decision-makers for the first time to assess public health risks, treatment requirements and efficiencies, and the potential for runoff recycling. The great system stability of the innovation and minor water quality data variability between individual experimental pavement systems provide good evidence for the controlled engineered application of this novel sustainable technology. (C) 2008 Society of Chemical Industry