Ambient Temperature
This is the only climatic parameter that has been directly correlated with biofilm thickness. The season, hours of sunlight and wind velocity all have minimal effect, whereas the higher the ambient temperature, the thicker the biofilm.

Water Flow rate
An increase in the water flow increases the transport of available nutrients. This allows greater diffusion of nutrients to the surface resulting in an increase in biofilm thickness. However, a flow rate increase also increases shear forces, which can reduce microbial attachment and remove attached biomass through hydrodynamic erosion. Therefore, in terms of water flow rates, biofilm thickness is determined by the relative strength of these growth stimulating forces versus the shear removal forces of the water velocity.

Nitrogen Availability
A high nutrient concentration of nitrogen can lead to the development of substantial biofilms. If nutrients are made more available, then biofilm growth will tend to increase.

System Surfaces
A surface will favor biofilm growth if it encourages molecular and microbial adhesion, therefore a rough surface will biofoul more easily than a smooth metal surface. Some surfaces may inhibit biofilm growth (e.g. copper alloy materials).

System pH
A neutral pH in the water system is optimal for the growth of most biofilm bacteria. The biofilm pH will almost certainly not be the same as the bulk water.

Concentration of Inorganic Particles
Suspended inorganic particles can aid hydrodynamic erosion of biofilms, however, they can also become entrapped in biofilms providing additional attachment sites for the microbial cells.

System Flushing
An increase in the frequency of flushing will lead to a reduction in the concentration of numerous particles present in the distribution system. This in turn provides for a slower biofilm development.