Poor Management of Processing Wastes
Environmental Assessment: Pressure State Response Indicators

The impact of the discharge of processing wastes is largely associated with the impact on water quality, this in turn affects aquatic ecosystems, and, through decrease in water quality, human health. | Pressure State Response Further Reading

These problems will increase as demand for animal proteins and animal products increases. Given the general patterns of urban growth, these potentially polluting activities will become ever more concentrated in peri-urban areas. The result will be increasing problems of waste treatment and disposal as the inherent capacity to absorb wastes within natural systems is exceeded.

However, in themselves these problems are not insurmountable, merely costly. The treatment requirements for disolved organic matter and suspended organic and in-organic solids is similar to the treatment requirements for domestic sewage. There is therefore no reason that wastes could not be adequately managed, apart from the costs.

The exception to this is the treatment of tannery wastes where there is a requirement to remove specific toxic compounds from the discharge.

Pressure

The pressure of industrial scale processing of animal products is cumulative and incremental. Many of the impacts of the waste products are similar to those resulting from animal production systems, with which they are likely to be associated, and with similar impacts to domestic sewage and solid waste.

It is therefore necessary to evaluate the pressure from processing industries within the context of the incremental effects of other sources of urban and peri-urban pollution.

Pressure is characterised by:

- The type of enterprise - Slaughterhouse, Tanneries, Milk Processing;
- The scale of the enterprise - small, medium or large;
- The technology used - high, medium or low;
- Proportion of by-product utilised in other processes.
- The method used for solid and liquid waste treatment and disposal;
- The number of similar or comparable enterprises discharging waste - including those from other sectors.

The impact of any individual enterprise is largely defined by the technology used, and the end product.

Meat processing can use as much as 60 cubic metres of water per metric ton of product. Frequently the waste water is discharged at high temperatures, with a high organic and nitrogen content. The waste water may also carry pathogens, including salmonella and shigella bacteria, parasite eggs and amoebic cysts. Chloride levels are often high as a result of curing and pickling processes.

Tanning, again using high quantities of water (20 to 80 Cubic metres of water per ton of hide) produces very similar by-products - solid wastes can represent up to 70% of the wet weight of the original hides.

In both cases the technology used to process waste determines the impacts. As an initial step, dry removal of solids followed by screening to remove suspended solids and emulsified fats will reduce pollutant loads. Pre-treatment of wastewater can bring discharge to levels where disposal can take place through municipal sewage systems, if capacity exists. However, at the other extreme, treatment is often limited to dilution and discharge into open water systems.

Milk processing, while using less volume of water per tone of product also generates considerable organic waste, including suspended solids and emulsified fats. There is however considerable potential for the use of waste products - milk, fat and whey - in lower grade products such as animal feeds. Again pre-treatment of effluents can allow discharge into municipal systems.

The additional problem with tanneries is the use of chromium and other toxic materials (Trivalent chromium sulphate; Arsenic and cyanide as sharpening agents; Sulphuric acid). Technologies have been available since the 1970s to retrieve chrome, however this tends to be through the treatment of waste water in specialist facilities rather than on site.

In summary, the key pressure factors are the total number of comparable polluting activities, and the level of technology used in processing and waste treatment.

State

Clearly there are changes in the environment that result from the discharge of untreated (and treated) effluents. While few of these changes can be considered benign, this brings up the question as to what are acceptable limits to change - clearly it is not realistic to try to maintain the whole environment in pristine condition. It is therefore necessary to define the desired environmental quality in terms of alternate use options.

The process of defining acceptable environmental changes, in other words acceptable discharge levels, will involve negotiation between the different stakeholders, including sectoral downstream users, and the need to maintain ecosystem functioning.

The end pathway for the impact of effluents from the industrial processing industries is aquatic the ecosystems. However, the knock on effects and direct impacts while in this pathway include health impacts. The effects of organic load and particularly nutrient load are similar to the impact of the disposal of animal manure. The increase in nutrient load can result in eutrophication and a change in species mix and loss of species.

But by the time these impacts have resulted in macro-changes it is often too late to reverse the damage. As a result there is a need to predict changes to state before they occur, in order to avert problems. The tendency is to regulate using discharge criteria, rather than state criteria, and then to try to link "acceptable discharge" to environmental standards.

The most common indicators are therefore those that assess adherence to regulation rather than assess response to impacts.

The major problem is then to define what are damaging, or alternatively, acceptable levels of pollution. But this will vary according to the downstream requirements of the system, water quality for industry may have fairly low requirements, while discharge for ecosystem functioning may be higher than for industry but less critical than supplies used for drinking water.

In addition to the need to define the downstream use of water, care must be taken in seasonal variations in discharge, and possibly more critically dilution within the water body.

State indicators are characterised directly by:

- Presence or loss of indicator species - vegetation and microfauna;
- Gross changes in ecosystem or habitat;
- Presence and concentration of pollutants in the water body or soil.

However, in most cases it is the proxy indicators of discharge that are used to assess state:

- Concentration of pollutants in factory effluent at the source;
- Concentration of pollutants in discharge water at the point of discharge to the aquatic system.

Frequent sampling may be needed to identify the impacts resulting from seasonal changes in water flow; discharge of effluents during low flow conditions will have much greater impacts than during flood periods. The problem may be compounded by the temperature of discharge water, with warmer water compounding problems of high nutrient load.

Response

In most cases industrial processing systems are regulated under similar arrangements to other industrial systems, through a series of regulations designed to encourage sound management practices and discourage polluting activities. The problems occur when there is a lack of knowledge on what constitute sound management practices.

The most common response indicators are to use emission guidelines and policing of compliance to those guidelines.

Response is characterised by:

- The existence of emission regulations;
- Compliance with emission regulations;
- Policing of emission regulations;
- Existence of regulations on required technology;
- Monitoring effort by regulating agencies;
- Financial mechanisms to encourage use of low polluting management;

And given that emission regulations are based on best available knowledge:

- Research in support of development of improved technologies; and
- Changes in emission regulations in response to feedback from monitoring programmes.

Further Reading

World Bank (1998) Pollution Prevention and Abatement Handbook

[Livestock & Environment Toolbox Home]