Water pollution occurs when undesirable efluents disperse in a water system and so water quality change $()$

Water pollution in natural Sources: include thermal and acid effuents from voleanic areas $()$

Algae are undesirable because they cause bad odors and flavon in water $()$

Algue may produce toxie materials of potential danger to human. $)$

Algal growth favored by warm water temperatures$()$

Algae not produce toxic materials and not danger to human. $()$

When algae float to the surfice and they become concentrated Bacteria attack and decompose them causing increasing oxygen. $(g)$

When Algal growth the organic matter back into the water, thus increasing the COD. $()$

Algal growth in reservoirs controlled by the application of soudiom hydroxide. $()$

In many water supplies, copper sulfate is applied routinely from two to four dayes. $()$

Copper sulfate use in reservoirs must be carefully controlled because copper sulfate is toxic to fish and in high doses to humans $($T$)$

Algal growth in swimming pools causes an unsightly stime on the walls of the pool and reduces water clarity $()$

When Algal growth the organic matter back into the water, thus increasing the $)$

When BOD increasing that causing a deterioration of water quality. $()$

Nitrate and phosphate are especially important in water pollution $()$

When the water becomes anaerobic, many animals such as fish increase. $()$

The consumption of oxygen by bacteria is called the COD. $($F$)$

The BOD test incubating the sample for the standard period $($usually tow days at $20C).()$

The fecal coliform group can grow at an elevated temperature of $-44\mathrm{.}5C.()$

Sedimentation mean the materials Silt and sink to the top. $()$