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3.11 Microbiological Wastewater

Treatment Technical

Description Microbiological treatment of highly organic wastewaters is rather simple but expensive technology that is mainly used to treat septic tanks, grease traps, industrial settlers, liquid waste disposal ponds, and highly polluted waterbodies, etc., by enhancing naturally-occurring bacterial populations. One example of this type of treatment is the BIO 2000® system, which uses a Lactobacillus inoculum (250 000 cells/ml) to decompose organic wastes. Under organic carbon-rich conditions, the initial inoculum of bacteria doubles approximately every 20 minutes and maintains this growth rate as long as the amount of carbon is sufficient for bacterial growth. Excess bacteria generated during this process can be used as fertilizers, while the treated effluent can be reused for most purposes. Table 4 shows typical levels of microbial uptake of a range of water quality indicators that can be achieved using this technology.

TABLE 4. Typical Water Quality Improvement Using Microbiological Treatment.

Extent of Use

This method has been well tested in Latvia, and has been used in the reconstruction of biological wastewater treatment plants that treat wastewaters from the meat processing industry and wastewater from zoological gardens. Between 1995 and 1997, 4 septic tanks, 2 grease traps, 2 sludge repositories, and 2 greenhouse waste disposal sites were treated using this technology, with excellent results. There are currently a further 10 projects using this technology underway.

Operation and Maintenance

This technology requires a very small staff to implement. The production of the bacterial inoculum, however, requires highly specialised staff and facilities. Nevertheless, such staff and facilities can service numerous treatment facilities.

Level of Involvement

This technology is generally applied by district and local level administrations.

Costs

This technology has a relatively low investment cost (excluding the microbiological laboratory). Commercially available bacterial inocula cost about $200/100 g unit.

Effectiveness of the Technology

This technology can be used to treat approximately 1 400 to 2 000 m² of water surface, or 300 to 500 m³ of manure of liquid wastes. The treatment is normally applied as a single step in surface waters and repeated after 3 to 6 months in the case of wastewater treatment use.

Suitability

This method can be used in wastewater treatment, waste treatment, fatty waste treatment including treatment of wastewater from animal processing activities, and treatment of artificial ponds and polluted surface waters.

Advantages

This technology has little or no energy demand. Excess bacteria produced by this technology may be used as fertilizer.

Disadvantages

The technology is expensive if used on a large scale. Currently, the marketing of this technology is proprietary and under the control of a single (US) company.

Cultural Acceptability

There are no known problems of cultural acceptability associate with this innovative treatment method.

Further Development of the Technology

More investigation of the efficacy of this technology is needed.

Information Sources

Rolands Bebris, Ministry of Environmental Protection and Regional Development, 25 Peldu Str., 1494 Riga, Latvia, Tel. (371-7) 227145, fax: (371-7) 820442, e-mail: BEBRI@VARAM.GOV.LV.

Anna Egle, V/U "Meliorprojects", 11 Novembra Bulvaris 31, LV-1494 Riga, Latvia, Tel. (371-7) 228734.

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