Empirical models for change in pH and temperature within gravity-based reactor columns

Abstract: Column reactor models of volume size 3,000  and 1,500 cm3 are made using organic materials such as sawdust and immature (drumstick) Moringa oleifera and other natural materials such as gravels (6 mm size) and ball clay available locally at Jodhpur, India. Water is passed through these porous reactors under gravity at once. The experiments were aimed at finding low-cost solutions for wastewater or sewage disposal at point of use. The change in pH during water filtration experiments is measured and modelled as functions of X1 (column height), X2 (flow rate), X3 (cumulative percolation time) and X4 (change in electrical conductivity). The parameters X1, X2, X3 and X4 are found to be highly correlated to each other irrespective of materials used for making the bioreactors. There is a hyperbolic relationship between temperature gradient within the porous material column bed through which water is percolating and time taken during that process. The temperature distribution in the gravel or sawdust media reactors is not influenced by the inflow rate or height of the reactor column used for experimentation. Distinct temperature distribution exists at each depth of the heterogeneous reactors. The multi-parameter model developed and the hyperbolic relationships help to characterize the efficacy of bioreactors. The effect of the materials on the wastewater treatment can now be individually evaluated using the multi-parameter approach presented in this paper.