Fellmongery, Tanning and Meat Processing Projects

Treat liming, wet blue, other general liquors and slaughter, stockyard and rendering wastes

Clients: Multiple skin processing plants

Period: Various

Location: Ashburton, Hastings, Napier, Shanon, TeAroha, Dunedin, Gisborne, Fielding, Auckland and Marlborough.

Fellmongery plant sulphide oxidation waste liquor treatment

• Hydrogen sulphide gas extract and scrubber systems, incl. chemical storage and dosing

• Skin processing mellow lime

• Tanning chromium precipitation and recycle

• Fellmongery biological treatment plant and solids handling.

• Process chemicals preparation, storage and transfer

• Fellmongery paint table chemicals preparation and transfer

• Washwater improvements and minimisation

• Stockyard water management improvement practices

• Flow balancing and mixing

• Sludge dewatering and transfer

Fellmongery Projects

Peter has audited and designed wet systems handling at a number of new and existing fellmongery and meat processing plants around New Zealand.

Spent process liquors are usually batch treated and blended to lessen their effect when released to tradewaste or other on-site treatment systems. Skin or hide processing in fellmongery plants to green slat stage results in high sulphide liquors that cause acid degradation of cementitious pipe networks and causes hazardous gases at municipal wastewater treatment works.

Sulphide oxidation facilities change the typically green liming liquors to a milo-coloured liquid that symbolises conversion of most sulphides to thiosulphates. The process involves reaction of manganese sulphate with the skin processing sulphide rich liquor in the presence of oxygen that is normally provided by aeration. The conversion process reaction time ranges in practice from 4 to 6 hours depending on the system setup and reagent addition rate. Foam causes a float that may contain fractions of partially treated sulphide.

These plants need active systems to control foaming, completely mix the contents and adequately flush all solids from waste liquor process vessels at the end of each treatment cycle. Mellow lime systems have been designed to promote chemical efficiency. Clients also report improved product quality with mellow lime processing.

Tanning Projects

Wet blue tanning of skins or hides often involves the use high exhaust chromium. Where high exhaust chromium is insufficient to meet regulatory requirements, clients have found moving to chromium precipitation and recycle has attractive cost benefits.

The recycle process requires that acid is added during the pre-treatment process before chromium is returned to the wet blue process step. This results in the release of proteins and fats that in excess will inhibit the uptake of chromium. It is therefore important that these excesses are reduced before the chromium liquor is recycled.

Meat Plant Projects

Meat plant projects usually involve optimising of slaughter non-foods capture systems to prevent their entry into waste streams and treatment of general site wastewater to meet regulatory limits. The treatment of meat processing wastewater incorporates screening to remove solids such as paunch wastes and other methods to remove grease and protein to comply with tradewaste limits. More sophisticated treatment is needed to provide an acceptable quality for disposal to irrigation and surface water.

A recent large project found that physical-chemical methods proved to be cost competitive over biological systems, particularly where high calorific value waste is used for energy recovery and other waste solids can be disposed to composting or similar. Meat processing wastewaters required to meet stringent viral and pathogenic indicator limits are expensive to achieve by using biological wastewater treatment methods and therefore usually use a ultraviolet and/or physical-chemical treatment plant addition.

For further information call Peter Browne at Enviromex NZ Ph 09 9504463 or 021 576 005

Back to About Enviromex NZ

Back to Project Summary Slideshow