Urban wastewater and industrial wastewater contain a large number of N, P and other nutrients. However, the conventional secondary wastewater treatment process can only remove most of the organic pollutants, and the removal effect of nitrogen and phosphorus is poor. Chemical method can achieve better removal effect by forming precipitates with pollutants such as aluminum salt or iron salt, but the cost of chemical agents is high, and a large number of chemical sludge formed is difficult to treat. In view of the fact that microalgae can absorb various inorganic nitrogen and organic nitrogen, and can remove inorganic N and P without switching between multiple operating conditions, we designed and developed a microalgae incubator to reduce the cost of wastewater treatment. Mature microalgae can also be used as raw materials for other products, bringing extra profits.
The growth rate of microalgae is closely related to its environment. We use sensors to obtain environmental parameters, using single-chip control of environmental regulation equipment, so that microalgae in the most comfortable growth environment.
The incubator is composed of wastewater filter box, frame, incubator box, distribution box, drainage pipe and environmental monitoring and regulation system. The environmental monitoring and regulation system consists of temperature sensor, heating rod, cooler, air pump, gas distributor, light intensity sensor, LED lamp and CO2 sensor. As shown in Fig1.
Fig1. Equipment Structure Diagram
When the equipment starts to work, the wastewater flows through the filter box to remove the solid impurities in the water, and then enters the incubator. The ultraviolet germicidal lamp in the incubator worked for 10 minutes to eliminate microorganisms in the water (see Fig2a. ). The temperature sensor detects the water temperature information and transmits it to the Single-Chip Microcomputer. The Single-Chip Microcomputer controls the heating rod or the refrigerator to adjust the water temperature to a suitable temperature (see Fig2b. ). At this time, microalgae was added to start the culture (see Fig2c. ). At 6 am every day, the microalgae enters the bright cycle of the photoperiod, and all the light plates remain open to supplement the light for the microalgae ( see Fig2d. ). When the ambient light intensity is higher than 10000 lux, the side LED light board is extinguished. During this period of the light cycle, when the ambient light intensity is less than 10000lux, the side of the LED light plate is lit. After 6 p.m. every day, the microalgae enters a dark cycle, and all light plates are turned off ( see Fig2e. ). The gas distributor arranged in the box will work regularly, working for 30 minutes every 6 hours, stirring the microalgae in the box to make it evenly distributed. After the wastewater is purified to the discharge standard, the water flows out through the discharge port and the microalgae is collected ( see Fig2f. ). If the discharge standard is not met, return to the step of adding microalgae until the wastewater reaches the discharge standard and then discharged. The work flow chart is shown in Fig3.
Fig2. Workflow Demonstration Diagram. ( a ) Turn on the UV lamp ; ( b ) Water temperature regulation ; ( c ) Adding microalgae ; ( d ) Supplemental lighting ; ( e ) Turn off the lights ; ( f ) Collecting microalgae ;
Fig3. Workflow Diagram
2.4.1 Advantages
The hardware produced by our team has been granted a Chinese patent, and our team has effectively communicated and coordinated with the company and signed a technology transfer agreement with the company in 2023.Fig4. is a patent authorization notice. ( You can download the patent specification at the end of the article )
(a)
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Fig4. Patent Authorization Notice
（a）Chinese Version（b）English Version
This hardware has the following advantages:
1) Environmentally friendly
The conditions for removing inorganic nitrogen, phosphorus and other substances in wastewater by microalgae are less and will not cause secondary pollution. Microalgae fix carbon dioxide in the air when they grow, which helps to mitigate the greenhouse effect.
2) Turn wastewater into valuable products
Microalgae can use N, P inorganic salts and other nutrients in wastewater to save culture costs. The cultured microalgae can be used not only for agricultural fertilizers and health products, but also for the production of biodiesel, polyunsaturated fatty acids, pigments and polysaccharides. The water purified by microalgae can be used for farmland irrigation.Realize the primary utilization and secondry proliferation of microalage products.
3) Low cost
The price of 80L column photobioreactor on the market is $1000 - $1200; Our current incubator capacity is 24L, and the cost is $163. When the capacity is increased to 80L, the cost of the incubator is $310, which is far lower than the price of the column photobioreactor on the market.
4) Biosafety
Photobioreactor is a closed system, forming a relatively safe living environment. Compared with open reactor, microalgae is not easy to leak and pollute the external environment. At the same time, the microalgae input is the immobilized algal globule:①It can effectively isolate the pollution of the mixed bacteria and algae in the water and ensure the growth of microalgae;②It can effectively reduce the cost of microalgae collection; ③It can effectively prevent biological escape.
5) Built in uninterruptible power supply (UPS)
It plays a stabilizing role for the equipment and ensures the service life of the equipment; It can prevent the power consumption problem in case of power failure, and also protect the normal operation of the load.
6) Multiple sampling points
According to actual needs, water samples at different stages and algal globules at different growth periods can be separated through different sampling points, which is convenient and fast.
2.4.2 Disadvantages
1 ) Volume is a little small, can not meet the daily amount of wastewater treatment ( factory wastewater produced at least a few tons or even dozens of tons of wastewater per day )
Due to site constraints, we have not yet done a large-scale pilot experiment. But in the future we will try larger photobioreactors. It is believed that our photobioreactor will be put into use by the factory in the future !
We package the equipment-related design drawings with the code and attach the parts list and price of the equipment. Click the button below to obtain.
