Since the first time we tested the MDU, some important changes have made based on the recommendations from the first testing. The changes include the addition of safety components in a vacuum system which has been the main sludge pumping mechanism option. The second thing is the mobility issue with the two-wheeled tractor. Though this has been a great idea, it faces the user friendliness with heavy mobility challenges, low speed, needs not only two people to operate but more people needed. Difficult to maneuver like crossing busy roads, bumpy roads especially when the tank is full. Hence; the two-wheel tractor is replaced by a 4 wheel-tractor as shown in the picture.