NEW Wastewater Treatment

Team NEWater has the goal of developing an autonomous mixing and injection system to help aid the current N-E-W Tech(TM) BioChar Filtration System.

Design Task
The injection system must be capable of autonomously and accurately injecting biochar into wastewater. The unit must also be able to be scaled-up to full industry standards and have an adjustable flow rate in order to vary the concentration of biochar in the wastewater.

Design Goals and Deliverables
1. Inject biochar solution at rates from 0.25-10g/L of water in a manner that can be scaled upwards to meet industry standards.

2. Meter rates of injection within 10% of actual concentration.

3. Automated control of BioChar mixture and injection rates to suit varying water conditions.

4. System must be safe to operate and be mobile with existing container/vehicle combination.

Design Selection
We settled on this design for a number of reasons. First was our budget, which ended up being more constrained than we previously believed. We attempted to keep the total cost of our design below $3500, which meant that we were unable to purchase a Versi-feeder or a SLIM mixer. The SLIM mixer also would have broken the biochar down into smaller particles, which would destroy the ability it has to attach to nutrients in the wastewater and make it harder to filter. Our budget constraints also made selection of a flow meter very difficult, as metering as low of a flow as ours requires a flow meter which costs several thousand dollars. We also were constrained in our flow meter selection due to the abrasive nature of the biochar, which requires a robust metering system. The biochar/water mixture is also dosed with iron, which makes a magnetic flow meter inaccurate.

SLIM (Solid Liquid Injection Manifold)
When large amounts of powders need to be added quickly into liquid or hard-to-disperse solids take too long to completely incorporate, an inline high shear mixer with sub-surface powder injection capabilities is extremely worth considering. The problem that lies here is that most injection manifolds are made for industrial sized scaled. We are currently look at smaller scaled version to work with the mobile unit and how we can make a working laboratory version.

This system works perfectly for our needs because:

1. The water enters the mixer and immediately encounters the biochar through a vacuum created by the rotor.

2. Product is injected directly into a high shear zone suspending the biochar into the water.

3. Resulting mixture is expelled centrifugally through the stator openings in a high velocity to the system.



Agitator/Pump Combination
One idea we had was to use a 55-gallon drum to hold a mixture of biochar and water. This would need to be held in suspension in order to keep the concentration even throughout the mixture. We would use an agitator mounted to a drum to do this. This design would also require that there be an external pump to move the mixture of water and bichar to the wastewater.



VersiFeeder
Using a controlled vibration design for non-free-flowing materials the vibrator helps the biochar moved down the injection screw after being manually put in to the hopper. The D.C. drive motor is able to control the right amount of biochar from the feed to the injection point for further mixing.

Benefits of using the VersiFeeder:

1. Accurarcy of ±1-2%.

2. Easy to clean and break down.

3. Can scale for bigger applications and change in material used.

4. Volumetric rate capacity are 0.0037 to 0.037 CU.FT/HR which perfectly meets our BioChar mass needs.

Combination Idea


We also looked at a combination of other ideas to create a new design. We would load biochar into a 55-gallon plastic drum using a corkscrew-shaped device. In the drum the biochar mixes with water and is held in suspension by an agitator. We use a pump to draw the biochar/water mixture out of the drum and push it into the wastewater pipe. We planned on using an ultrasonic or analog flow meter to measure the flow rate of the mixture as it goes into the wastewater. We also would have used a system of two check valves to regulate the flow of biochar into the wastewater and allow for a return pipe to help remove any residual biochar that may clog the injection site. The return pipe would be routed back to the 55-gallon drum.