Study On Modification Of The River Vertical Hard Revetment

Vertical hard revetment can change the morphology of the river, with results of destroyed features, degraded biodiversity, decreased self-purification ability and deteriorated water quality. A technology using prefabricated porous concrete to modify widespread vertical hard revetment was examined in current work. Six kinds of porous concrete with different void ratio, aggregate size and water-cement ratio were prepared to investigate the compressive strength and water purification properties. A river simulator device was used to determine the water purification capacity of the porous concrete in flowing condition. Water quality purification mechanism of porous concrete was discussed through the analysis of microbial community diversity. Vegetative filter substrate and plant types were determined through vegetative test and plant resistance test. Practical effects and existing problems were considered during the construction of demonstration project.(1) Results showed that the compressive strength and water purification ability of porous concrete were higher when the void ratio, size of the aggregate material, and water-cement ratio were 30%,10?20mm, and 0.30, respectively. The compressive strength of porous concrete was 8.23MPa. Under the hydraulic retention time of 6 days, the removal rates of CODMn, NH3-N, TN and TP were 54.8%,65.5%,42.2% and 12.5%, respectively.(2) Pilot experimental results revealed that prefabricated porous concrete was efficient for river water purification. Experiments carried out in the autumn under the hydraulic retention time of 6 days, revealed that the removal rates of CODMn, NH3-N, NO3-N, TN and TP were 49.5%,82.6%,25.1%,47.4% and 39.1%, respectively.(3) The diversity index and dilution curve showed that the total amount of attached microorganism and community diversity were much higher than the water suspended microbes. Species identification results showed the presence of different microbial communities including both aerobic bacteria and anaerobic bacteria, and nitrifying bacteria and denitrifying bacteria.(4) Plants could adapt to the vertical environment. Under satisfactory plant growth, the prefabricated porous concrete was fastened to the original hard revetment. This technology has good ecological and landscape effect.