Phosphorus removal from wastewater using rice husk and subsequent utilization of the waste residue

The removal of phosphor ions from an aqueous solution by adsorption by a low cost material, namely rice husk (RH), was investigated using different design parameters. The design parameters studied were the initial concentration of phosphorus (Co) (1–100 mg/l), the absorbance media bed height (hb) (10–100 cm), the pH of the phosphorus feed inlet (pH) (1-8), the treatment time (t) (1–60 min), feed flow rate (F) (5–100 ml/min), and feed temperature (Tf) (20–55°C). The results show that the percent removal efficiency decreased with increasing initial concentration and flow rate while it increased with increasing pH, absorbance material bed height, and feed temperature. The highest removal efficiency of phosphor ions achieved was 95.16% under optimum operating conditions (Co = 1 mg/l), (hb = 100 cm), and (pH 8), treatment time (t = 60 min), feed flow rate (F = 5 ml/min), and (Tf = 55°C). A statistical model was derived to find a general equation to relate all the operating parameters. Utilization of the huge amount of RH loaded with phosphor ions remaining after treatment in a useful method was also tested. One of these methods was to use the left over RH as cheap compost and this was tested for a tomato crop. In this way the process can present different benefits which are: to remove phosphor ions from contaminated water, to make good use of agricultural waste RH, and at the same time prepare a cheap fertilizer from the left over RH. This method can process a greater amount of waste in an economic and eco-friendly method.