The Removal Of Nitrogen And Phosphorus From Wastewater Using Enhanced AO-BAF System

Industrialization and Urbanization has been on the increase in recent times, This has lead to the use of more water and therefore leading to more wastewater as runoff in the system, Wastewater has been one of the major concern to environmentalist causing eutrophication and most importantly public health related diseases, This has lead to government enacting laws to govern the amount of organic and inorganic pollutants (nutrients) in wastewater getting into the environment. Most of the pollutants (nutrients) found in wastewater are nitrogen and phosphorus.This thesis objective was to determine the best condition for Nitrogen and Phosphorus removal from wastewater using Enhanced A/O Biological Aerated Filter (BAF) system that meets with the Chinese government environmental standard. Firstly the operating parameters factor of this study includes Air-water ratio, Reflux ratio, and Hydraulic load; these factors were investigated and evaluated. The best condition of each of these factors was selected, which was further used during the course of the experiment. After the selection of the best conditions for the various operating condition, there was an installation of an added unit/column to the rear of the ordinary AO-BAF system, where the effects of sponge iron mixed with zeolite and sponge iron mixed with manganese sand were investigated and compared on the removal of the desired pollutants. The AO-BAF system filter materials were composed of ceramic, zeolite, sponge iron and manganese sand. The following operational parameters were used:Reflux ratio was set at 100%,150%and 200%, Hydraulic load at 0.5m3/(m2·h),0.75m3/(m2·h) and 1.0m3/(m2·h), Air/Water ratio of 6:1(0.25 L/min),8:1(0.33 L/min) and 10:1(0.42 L/min). Each of these above parameters was investigated on their removal efficiency of COD, ammonia, total nitrogen and phosphorus, and the condition with the best removal rate in each factor was selected and used as constant for the other experiments. The removal efficiency of COD, ammonia, total phosphorus and nitrogen on various settings and filters materials, as well as the quantity of nitrifying bacteria, were compared at the end of the experiment. And it was shown that sponge iron mixed with manganese sand materials recorded the best removal efficiency of total phosphorus that meets the China's environmental standards of phosphorus effluents discharge into local water bodies. COD and ammonia also produced effluents that meet with the China's environmental standard. However, more research should be conducted on total nitrogen to find ways to improve its removal efficiency in an enhanced or ordinary AO-BAF system that will meet with international environmental discharge standards.