Algal-bacteria symbiosis system is a promising wastewater treatment technology through the interactive supply of O₂ and CO₂ to reduce the aeration energy and CO₂ emission. However, this innovation technology is hindered by limitations in field-scale application. One problem is that the implementation of existing algal-bacteria technology in urban areas is not practical because of the vast area needed for slower algae growth. Another problem is that algae suspended in the wastewater hinder photosynthesis efficiency. To address these shortcomings, this study has developed a vertical rotating algal-bacterial biofilm device, powered by a sunlight enhancement system, for purifying municipal wastewater. It has several practical advantages, including high photosynthesis efficiency, reduced land area requirement, low energy consumption, excellent nutrient utilization and minimal CO₂ emission.

This is how I came up with the idea for this project:

I have developed a vertical rotating algal-bacterial biofilm device to increase biomass by optimizing space utilization, as well as a sunlight enhancement system consisting of a sunlight tracker for tracking light, a Fresnel lens for condensing light, and a light guide plate for reflecting light to enhance the photosynthetic efficiency.

A Novel Practical Municipal Wastewater Treatment Device

Conventional municipal wastewater treatment processes based on activated sludge have shortcomings such as high energy consumption (~50% due to aeration), and significant greenhouse gas emissions. The use of environment-friendly and sustainable wastewater treatment systems is required. Algal-bacteria symbiosis system is a promising wastewater treatment technology through the interactive supply of O2 and CO2 to reduce the aeration energy and CO2 emission. However, this innovation technology is hindered by limitations in field-scale application. One problem is that the implementation of existing algal-bacteria technology in urban areas is not practical because of the vast area needed for slower algae growth. Another problem is that algae suspended in the wastewater hinder photosynthesis efficiency. To address these shortcomings, this study has developed a vertical rotating algal-bacterial biofilm device, powered by a sunlight enhancement system, for purifying municipal wastewater. First, through maximizing the space utilization to reduce the algae area required, the algal-bacterial was attached growth on the carrier to form a biofilm, biofilm carriers were vertically mounted on the wastewater tank. During operation, biofilm carriers were rotated evenly to alternate contact with the wastewater and air. It greatly increases the biomass per unit of sewage treatment and reduces the area. Second, to improve the photosynthesis efficiency, a sunlight enhancement system comprising solar tracker, Fresnel lens, and light-guide plates (LGP) was designed. The sunlight was focused through a Fresnel lens onto the LGP, in parallel between the two adjacent sets of biofilms to provide stable and sufficient light exposure to both sides. The lens was driven by a sunlight tracker always towards the sun. Using this device to treat synthetic municipal wastewater for more than 180 d, the biomass reached 56.7 g/m2, which is 4-6 times more than the conventional algal-bacterial device. The energy consumption stood at just 38% of the traditional activated sludge device. Removal of pollutants especial N was improved. The concentrations of effluent COD, NH4+-N and TN were well within the national discharge standards.