1. Definitions

Waste is movable objects which the owner wishes to dispose of (subjective definition of waste) or whose controlled disposal is necessary to ensure the well-being of the general public and in particular the protection of the environment (objective definition of waste). Regarding the distinction from hazardous waste, see environmental brief Disposal of Hazardous Waste. Waste disposal comprises the collection, transport, treatment, storage (intermediate storage), dumping and recycling of waste. The avoidance and minimisation of waste does not form part of waste disposal. They are in fact another part of waste management.

Waste management comprises the sum total of all measures for the avoidance and minimisation as well as the controlled and environmentally acceptable disposal of waste of all types, i.e. domestic waste as well as commercial and industrial waste.

The generally accepted rules of the art include those rules which have been tested in practical applications, whereby the majority of the people working in this specialist field regard the processes, plant, facilities or operating methods as correct (3). The technical nature of the rules may vary according to the requirements in individual countries.

The state of the art is the state of development of advanced processes, plant, facilities or operating methods, guaranteeing the practical suitability of one of such technical measures. To determine the state of the art, an assessment must be made in particular of comparable processes, plant, facilities or operating methods which have been successfully tested during operation. The technical nature of the state of the art may vary according to requirements in individual countries (4).

2. Problems

The world-wide industrial development of recent decades with its effects on the manufacture of goods and on the consumption patterns of the population, particularly in areas of high population density, has led to an appreciable increase in the volume of waste. In this respect, targeted and target-group-related waste disposal (WD), involving careful analysis and taking into account not only the local conditions and options but also the environmental aspects of the relevant plant, can bring about the necessary improvements. As a rule, these relate to measures not only in the fields of waste management and waste technology, but also in the fields of law, administration, business management and organisation.

The necessary improvements should also aim to achieve reasonable representation for women, as one of the target groups, in the institutions and bodies responsible for waste disposal. This is the best way to guarantee that their legitimate interest in participating in the development and implementation of administrative, business and environmental monitoring will be served.

3. Objectives

The controlled disposal of domestic waste and commercial and industrial waste forms a vital part of the infrastructure of human settlements built on the principles of hygiene. It is an essential component of waste management, whose function must be to help

• to protect human health,

• to contribute to the quality of life by improving environmental conditions,

• to maintain the ecological equilibrium of the environment, particularly of the soil and groundwater, and - where it has been disturbed - to restore it,

• to ensure safe disposal of the waste produced by the population as well as by commercial and industrial establishments, depending on the quantity and type of the waste and taking into account the need for avoidance and minimisation, ensuring the long-term sustainability of resources which serve the well-being of the general public and the legitimate needs of individuals.

Figures show that in many countries there is a marked imbalance between waste production and controlled waste disposal. This is because in the countries in question a clear priority has been given to the matter of industrial development, without however paying at least equal attention to the necessary development of waste disposal facilities.

Very often this relates to waste arising from imported industrial goods. There are seldom incentives to avoid waste.

4. Stages of waste disposal

The area of waste disposal (WD) comprises the following disposal stages:

• waste collection and transport (separate collection where applicable)

• waste treatment

• intermediate waste storage

• waste dumping (landfill) and

• waste recycling.

The disposal stages or steps apply to both domestic and commercial and industrial waste. It is not always absolutely necessary, or even advisable, to follow all of these stages; rather, combinations of certain of these steps may be technically the best solution.

Waste transport (in collection vehicles) mostly involves the movement of empty, part-full and full vehicles, but also includes processes for emptying vehicles in transfer stations and treatment plants as well as at landfill sites. The object of waste transport (in special vehicles) is to transport waste between transfer stations and the relevant disposal plants. One must always consider whether the distance between the collection area and disposal plant (e.g. landfill site) has become uneconomic and, if so, provide transfer stations. Within this environmental brief, the transfer of waste is also considered as waste transport.

Within waste treatment the following processes in particular may be used:

· biological processes

a) aerobic processes:

• in liquid phase (aeration)

• in solid phase (composting)

b) anaerobic processes (fermentation/biogas extraction):

• single-phase systems (mixing reactor; solid-bed reactor)

• two-phase systems (hydrolysis with complete mixing; solid-bed hydrolysis)

· chemical processes: precipitation/flocculation, neutralisation, oxidation, reduction etc.

· physical processes: sorting; decanting, dewatering, drying; reverse osmosis, ultrafiltration, emulsion separation etc.

Intermediate waste storage may be important if waste must be temporarily stored in fixed installations, because for economic or process technology reasons it cannot be transported directly for recycling, treatment or landfill.

Waste dumping is a method of controlled final disposal at landfill sites which must be done using state-of-the-art methods (base sealing, treatment of percolation water, landfill gas disposal/utilisation etc.). Waste dumping to some extent represents the final stage of any disposal sequence, regardless of the detailed technical structure of the sequence. The only exception is where waste substances or residues are fully recycled (e.g. agricultural use of sewage sludge, used glass recycling etc.).

Waste recycling includes all processes (methods) for recovering or utilising valuable materials in waste. The principal waste recycling processes are:

• material recycling (e.g. of used glass, used oil, waste paper, plastics, metals etc.)

• liquid phase aeration, composting, biogas extraction (these processes also represent processes of biological waste treatment; see above)

• incineration (utilisation of waste heat, incineration residues)

• agricultural sewage sludge utilisation.

The environmental impacts of the above-mentioned types of waste disposal should first be considered in isolation in order to assess their importance. An integrated assessment should then be carried out for the project, also taking into account any significant interactions.