Lesson Learned: Technology Selection

​Problem: A greenhouse facility wants to reuse water from a flood floor which is used to water potted plants. The water collected has vermiculite and organic matter clouding the water which would clog nozzles and settle in pipes.
 
Solution: The operator looked at two different technologies, a self-indexing filter and a parabolic filter screen (Figures 1 & 2). Both are recommended units that filter coarse material from water.

Figure 1: Diagram of a self-indexing filter [level sensor is tripped when water rises due to clogged paper and roll is unspooled]

Figure 2: Diagram of a parabolic filter screen [(a) inflow; (b) flows onto screen; (c) waste remains on screen and treated water falls through; (d) waste exits through tray; (e) treated water exits through (f); (g) water overflows if screen becomes clogged and exits through (f)]

​Discussion: The infrastructure required for either technology is similar; both will need some plumbing and a pump to move water through the treatment system. The technologies are compared in the table below. Both systems will complete the task; the self-indexing filter is more hands-off but requires more inputs. The parabolic filter screen must be supervised but has minimal on-going costs.

​Decision: The operator choses the self-indexing filter as it requires less regular supervision. The additional energy costs, on-going need of paper rolls, and disposal of paper was preferable to increased labour requirements and disposal of waste.
 
Lesson Learned: When there are multiple technologies that could fit in a treatment system it is important to investigate all aspects. Decisions should be made based on more factors than merely cost.