Filtration to Eliminate <i>Phytophthora</i> spp. from Recirculating Water Systems in Commercial Nurseries

Fig. 5. Mechanical scraping and raking of the clogged layer and the re-filling of the slow sand filters: (C) tractor with blade used to level sand surfaces.



Image from Plant Health Progress article:
Filtration to Eliminate Phytophthora spp. from Recirculating Water Systems in Commercial Nurseries