well-studied substances.Endocrine (Blood secreting glands) disrupting capacity Lindane and DDT most toxic (also the most active as pesticide) Hexachlorocyclohexane (also called lindane) hazardous due to their persistence and bioaccumulity. Likely to have long-range effects organochlorines (Ocs)
have lower aquatic toxicity than synthetic pyrethroids and are less persistent than organochlorines. Nevertheless they have high human toxicity Organophosphates (Ops) show high aquatic toxicity The synthetic pyrethroid insecticides (SPs)
Wool from the majority of grower nations contains residual sheep treatment medicines which are used legally to control infestations of lice. ticks and mites.
The presence of these materials on wool is variable and depends on the permitted legal use pattern in each country.
All major grower countries have banned the use of organochlorine pesticides for sheep treatment,
there is evidence that wool from some former Soviet Union States and South America contain lindane at detectable concentrations
Wool scouring Environment issues Potential for pollution of water The removal of contaminants present on the raw fibre leads to the discharge of an effluent main polluting contributors are:
• highly concentrated organic material in suspension and in solution,
dirt in suspension
• micro-pollutants resulting from the veterinary medicines applied to protect sheep from external parasites.
These high levels of oxygen-depleting substances must be removed from the effluent before it can be discharged to the environment without potential for harmful effects.
when they enter the scouring process, a distinction has to be made between
Lipophilic (Hydrophobic) and
lipophilic compounds - OCs, OPs and SPs - associate strongly with the wool grease
removed with it during scouring (although a fraction -up to 4 %-is retained by the fibre and will be released in the subsequent wet processes).
This behaviour applies also to diflubenzuron (IGR).
Recent studies have shown that triflumuron (IGR) associates partially with the dirt and partially with the grease. As a result, compared to other lipophilic compounds, a higher proportion of this pesticide is likely to be retained on-site (on the wool fibre and on the recovered wool grease and dirt) and not be discharged in the aqueous effluent
IGRs such as cyromazine and dicyclanil are appreciably water-soluble (I I g/l at 20 °C for cyromazine).
not removed in wool grease recovery systems.
In the waste water treatment systems an additional fraction of the pesticide residues is removed by
Physico-chemical separation techniques remove the biocide residue along with grease and the dirt with which they are associated.
evaporation system removes Ocs and SPs in significant quantities. But upto 30% of Ops may appear in the condensate because they are steam volatile.
The water-soluble compounds, such as the IGR cyromazine are probably not removed from the effluent stream except by evaporating treatments
Despite these treatments, the removal of pesticides is often incomplete and there is potential for pesticides to enter the aquatic environment when the effluent is discharged The environmental concentrations of ectoparasiticides in the receiving water depend greatly on local circumstances, in particular, the amount of scouring activity concentrated in a given catchment and the dilution available between scouring discharges and the river which receives the treated effluent. The control of the discharge limits at the scouring mills is carried out by comparing with standards.
Potential for pollution of land Two main "wastes", grease and sludge, are produced as a consequence of scouring activities (and related effluent treatment). it may be possible to recover from 20 to 40 % of the grease initially present on the raw wool This is to be regarded as a by-product rather than a waste, since it can be sold to lanolin refiners for the production of high-value products in the cosmetic industry However, high levels of pesticides residues in the grease can also be a problem for the lanolin refiners, especially for the production of lanolin-based pharmaceuticals and cosmetics more expensive and sophisticated techniques have to be used to reduce the pesticides to acceptable levels Acid-cracked grease has no market value and has to be landfilled
Potential for pollution of land (Contd) The sludge produced as a result of physico-chemical treatment of waste water also contains grease, dirt and the portion of pesticides which are strongly associated with either grease or dirt. Concentrates and sludges from evaporation or membrane filtration may also contain suint. which is mainly potassium chloride and potassium salts of fatty acids. Suint is a by-product which can be used in agriculture
Disposal of Concentrate and Sludge • incineration (with heat recovery) Pyrolysis/gasification • brick manufacturing • composting or co-composting with other organic material • landfill The first three sludge disposal routes destroy the organic material in the sludge, including grease and pesticides. The ash from incineration may contain potassium salts, derived from suint, and heavy metals characteristic of the soil on which the sheep producing the wool have grazed. The ash is normally disposed of to landfill
The characteristics of the char from pyrolysis/gasification are unknown and this char is also typically disposed of to landfill.
The use of wool scour sludges in brick manufacture results in no residues for immediate disposal
These three sludge disposal methods probably have the least potential to pollute land
Wool scour sludges cannot be composted alone, but require the addition of carbon-rich organic material. Green waste from agriculture or horticulture has been used.
Composting is not yet regarded as a fully developed, safe technique
only partly degrades the pesticides present in the sludge.
since the pesticides present in the sludge are because of their lipophilicity or
their strong propensity to absorb onto solids,
likely to be immobile in soil.
spreading of compost derived from wool scour sludges on agricultural land is unlikely to pose an environmental risk of any significance
Landfill is the simplest and often cheapest method of disposal of sludges.
In the longer term. however, landfill is not believed to be either economically or environmentally sustainable.
The fate of wool scour sludges in landfill is not known,
but there is a small potential for the Ectoparasiticides present to arise in leachate.
Anaerobic degradation of the organic material in the sludge will give rise to methane emissions
Potential for pollution of air
Air pollution is not a main issue for wool scouring processes.
Nevertheless two issues can be mentioned.
Hot acid cracking, which involves heating the scour effluent with sulphuric acid, when used near residential areas, has been the subject of odour complaints.
Incineration is used in conjunction with evaporation of the effluent because the surplus heat from the incinerator can be used in the evaporation process
Incineration of wool scour sludges has potential for air pollution.
Since sludges contain relatively high levels of chloride (from suint) as well as organically bound chlorine from ectoparasiticides etc.,
there is potential for the production of polychlorodibenzodioxins and furans, when they are incinerated
(catalytic and high temperature incinerators are now available to prevent these emissions). T
The sludges also contain relatively high levels of sulphur and nitrogen and
(the combustion process therefore produces SOx and N0x. Dust and odours should also be taken into account
Environmental issues associated with wool scouring (with organic solvent)
trichloroethylene cummunky used solvent.
Trichlorethylene is a non-biodegradable
Unaccounted losses of this solvent arising from spills, residues on the fibre,
if not adequately treated to destroy the solvent, may lead to diffuse emissions resulting in serious problems of soil and groundwater pollution.
Wool preparation before colouring Carbinsing Scouring, Drycleaning Fulling Bleaching
Wool pretreatment gives rise mainly to water emissions,
although there are also specific operations (e.g. carbonising and dry cleaning where halogenated organic solvents solvents can produce not only emissions to air, but also contamination of soil and groundwater if their handling and storage is not done using the necessary precautions.
The pollutants that can be found in the waste water, originate in part from the impurities that are already present on the fibre when it enters the process sequence and in part from the chemicals and auxiliaries used in the process.
Pollution originating from impurities present on the raw material Residues of pesticides used to prevent the sheep becoming infested with external parasites can still be found on scoured wool in amounts, which depend on the efficiency of the scouring process. These are mainly organophosphates (OPs) and synthetic pyrethroid (SPs) insecticides and insect growth regulators (IGRs), detectable residues of organochlorine pesticides (OCs) can be observed. They partition between the fibre and the water according to their stronger or weaker lipophylic character and, as a consequence, traces of these compounds are released in the waste water.
Spinning lubricants, knitting oils and other preparation agents also represent an important issue in wool pretreatment.
These substances are removed during the scouring process, contributing to the COD load and aquatic toxicity in the final effluent.
The main concerns are about:
• poorly refined mineral oils (content of aromatic hydrocarbons)
• APEO (non-biodegradable and giving rise to toxic metabolites)
• silicones (non-biodegradable and difficult to remove without scouring assistants)
• biocides (toxic to aquatic life).
Pollution originating from chemicals and auxiliaries used in the process
Considerable amounts of surfactants are used in pretreatment as detergents, wetting agents, etc.
Surfactants with good biodegradability with acceptable performance are now available
the use of alkylphenol ethoxylates (APEO) is still common in some companies due to their low cost
Alkylphenol ethoxylates (APEOs) and in particular nonylphenol ethoxylates (NPEs) are under pressure due to the reported negative effects of their metabolites (chemical reaction in living organisms) on the reproduction system of aquatic species.
Other pollutants of concern that may be found in water effluent from pretreatment activities are: • reducing agents from bleaching treatments and chemical setting of carpet wool yarn (sodium metabisulphite): they contribute to oxygen demand in the waste water • poorly bio-eliminable complexing agents (e.g. EDTA, DTPA, phosphonates) from hydrogen peroxide stabilisers, etc. • insect-resist agents in wool carpet yarn production