A.    Sludge processing

          Sludge presents or withdrawn from primary or simple sedimentation are as much as 97% water. Biological and many chemical sludges have higher water contents and are more difficult to the water than primary sludges.

B.    Technologies on Sludge Processing

1.    Sludge conditioning

          The purpose of sludge conditioning is to increase the rate and/or extent of dewatering achievable for a given sludge. The uses of sludge conditioning with the combination of dewatering reduces the moisture content of sludges.

          Another conditioning practices employ the addition of chemicals. Ferric chloride is added either alone or in combination with lime. The addition of lime is a fairly popular conditioner for primary raw sludge, and ferric  chloride alone has been used for conditioning biological sludges.

2.    Digestion

          The principal purposes of organic sludge digestion is to stabilized and render the sludge less putrescible to reduce the pathogenic content and tor educe the sludge quantity

Processes commonly use are:

a.    Anaerobic digestion

b.    Aerobic digestion

3.    Composting

          Composting will dewater sludge, destroy odor producing elements of sludge, destroy or reduce disease organisms and produce an anaesthetic and useful organic product.

Waste Disposal System

1.    Landfill – disposal facility where wastes are placed into and stored in the soil. The primary concern at landfill is to prevent groundwater contamination.

Prevention method include:

a.    Elimination of free liquid (liquid waste should be dewatered or solidified before placement)

b.    Diversion of surface water (run-on)

c.     Use of relatively impermeable daily and final cover minimize infiltration of precipitation

d.    Compaction of wastes

e.    Use of cells throughout the landfill

f.     Collection and treatment of leachate

g.    Groundwater monitoring

2.    Composting – biological decomposition of the organic constituents under controlled condition

a.    Aerobic composting

b.    Anaerobic composting

The materials can be decomposed as a result of the activity of bacteria, fungi, actinomycetes and protozoa present in the waste materials and of those are seeded from the atmosphere.

3.    Incineration – ultimate design process, applied to certain wastes that cannot be recycled, reused or safely deposited in a landfill site.

Incineration is need of:

a.    The waste is biologically hazardous

b.    It is resistant to biodegradation and persistent in the environment

c.     It is volatile and therefore easily dispersed

d.    It has a flash point below 40⁰C

e.    It cannot safely be disposed of in a landfill mercury, cadmium, zinc, nitrogen, phosphorous or sulfur

          Types of wastes that are incinerated:

a.    Solvent wastes

b.    Waste oils, oil emulsions and oil mixtures

c.     Hospital wastes

d.    Pesticides wastes

e.    Pharmaceutical wastes

f.     Refinery wastes such as tar and spent clay

g.    Phenolic wastes

h.    Grease and wax wastes

i.      Organic wastes containing halogen, sulfur, phosphorous or nitrogen compound

j.     Solid materials contaminated with hazardous chemicals (soil containing oil, capacitor containing polychlorinated bipheryls PCBs)

k.    Water contaminated with hazardous chemicals

4.    Recycling – refers to using the resources raw materials again, for the same or different purpose