Clay turbidity restricts light penetration in ponds. This reduces
the depth to which photosynthesis can occur and reduces primary
productivity
14
. Clay turbidity is caused by ultra-fine colloidal
particles, 1-10m in diameter. These particles carry a negative
charge which maintains them in suspension.
Positive ions react to reduce the negative charge of colloids,
causing them to coagulate into larger particles and settle out
2
.
Electrolytes with appropriate positive ions can therefore be added
to water to remove colloidal particles. Alum (aluminium sulfate),
hydrated lime (calcium hydroxide) and gypsum (calcium sulfate)
are often used as sources of electrolytes for reducing turbidity
14
.
Liming materials increase the concentration of calcium and
magnesium ions, which flocculate colloidal particles
14
. Gypsum
can also be used to flocculate colloids by increasing the
concentration of calcium ions
7
. However, in one comparative
study, alum was found to be more effective than lime or gypsum
in the reduction of turbidity. Alum reduced turbidity by 89-
97% within 48 hours at doses of 10-30 mg/litre
14
. The cost of
treatment with alum is significantly lower than for gypsum
7
.
Alum is acid forming and can substantially reduce total
alkalinity and pH as per the following reaction
Clay turbidity restricts light penetration in ponds. This reducesthe depth to which photosynthesis can occur and reduces primaryproductivity14. Clay turbidity is caused by ultra-fine colloidalparticles, 1-10m in diameter. These particles carry a negativecharge which maintains them in suspension.Positive ions react to reduce the negative charge of colloids,causing them to coagulate into larger particles and settle out2.Electrolytes with appropriate positive ions can therefore be addedto water to remove colloidal particles. Alum (aluminium sulfate),hydrated lime (calcium hydroxide) and gypsum (calcium sulfate)are often used as sources of electrolytes for reducing turbidity14.Liming materials increase the concentration of calcium andmagnesium ions, which flocculate colloidal particles14. Gypsumcan also be used to flocculate colloids by increasing theconcentration of calcium ions7. However, in one comparativestudy, alum was found to be more effective than lime or gypsumin the reduction of turbidity. Alum reduced turbidity by 89-97% within 48 hours at doses of 10-30 mg/litre14. The cost oftreatment with alum is significantly lower than for gypsum7.Alum is acid forming and can substantially reduce totalalkalinity and pH as per the following reaction
การแปล กรุณารอสักครู่..