0 to 14 has been established where pH value of 7 is neutral. A pH value less than 7 is acidic. A pH value above 7 is alkaline or basic. Table 10-5 lists pH values for some common materials. A pH value less than 7 in the wastewater plant influent may indicate septic conditions of wastewater. The pH values less than 5 and more than 10 usually indicate that industrial wastes exist and are not compatible with biological wastewater operations. Pretreatment of these wastes at the source is usually required since extreme pH values may damage biological treatment units.

Dissolved oxygen

Dissolved oxygen (DO) in wastewater has a great effect on the characteristics of the water.

Table 10-5. - Common Substance pH Values