|Sourcebook of Alternative Technologies for Freshwater Augmentation in East and Central Europe (UNEP-IETC, 1998)|
|Part B - Alternative technologies|
|3. Wastewater treatment technologies and reuse|
Recycling of wash water in the transportation industry can benefit not only transportation companies but also individual owners of motor vehicles. An example of the former is the use of recycled wash water by BORSOD VOL, one of the biggest bus transport companies operating in Borsod County, Hungary. In 1985, they installed a new, water-saving wastewater treatment facility for wastewaters resulting from washing at the central service plant. An example of the latter is the system for the treatment of oily wastewater from car washes introduced in Hungary during 1991.
The commercial transportation system uses detergent-free, high pressure, hot water to remove dirt and grime from the car bodies and engines of the buses. The resulting wastewater is mechanically treated in an OSZTVB-15 15 m³ capacity filter system, the main parts of which are dual filters, an aerator, and an Al2(SO4)3 and NaOCl dosing assembly. The filters consist of two layers: 1 mm to 2 mm diameter sand, and AQUAPOUR-D® activated carbon. For disinfection, a 1 to 3 mg/l NaOCl solution is used. The filters are backwashed with recycled water every 3 to 4 days. The polluted backwash water is returned to the treatment plant. Oily rainwater from the yard is also directed into the treatment plant.
The private system also uses fine sand filtration after pretreatment of the wastewater to remove grit, sand and oil. After this pretreatment, about 15% to 20% of the wastewater is discharged into a conventional sewerage system. This discharge prevents the accumulation of TDS and organic substances in the remaining water which is recycled for use in the carwash. This discharged water meets the water quality requirements for all categories. The remaining water that is to be recycled is subjected to ozonation (see the description of this technology elsewhere in this document) to prevent anaerobic digestion of organic materials which produces foul odours. After ozonation, the remaining, pretreated water is conveyed through a fine sand filter by pump. Once filtered, the water is resupplied to the carwash by means of a rubber membrane hydrophore at a pressure of between 2 and 8 bar.
Extent of Use
A few examples of similar technologies in Poland, Hungary and Latvia. Further, the private car wash recycling technology is being implemented in new petrol stations being built in Poland, Hungary, and Latvia, as well as those being renovated to meet new national environmental standards in those countries. While it is not unusual for modern petrol stations to include a car wash facility, high water prices create an urgent need for economical water use, which addressed through wash water recycling.
Operation and Maintenance
There is no need for highly trained personnel for operation. The systems are fully automated; only one-man supervision is required.
Level of Involvement
These technologies are usually implemented at the company level.
For the commercial vehicle washing recycling facility, the initial investment costs are about $80 000, with a further investment of about $1 600 likely to be required for reconstruction after about 10 years of operation. The initial investment in the private car wash recycling facility is somewhat less at about $20 000. Maintenance costs are about $4 000/year. The estimated period for recovery of this investment is about 1.3 years based upon typical usage within the region.
Effectiveness of the Technology
The achieved efficiency of water recycling is 80%.
Method suitable for use by public transportation firms and petrol stations with car washing facilities.
These technologies have an high treatment efficiency, easy maintenance, and simplicity of operation. The washing bays have a reliable construction, and, in the case of the public washing station, detergent-free operation.
Disadvantages of these technologies include the need for sludge treatment, especially in the case of the public system which does not discharge contaminated wastewaters to the public sewer system, and the danger of freezing during winter.
There are no barriers to cultural acceptance of these technologies.
Further Development of the Technology
The technologies are adequate to meet required standards for water savings and effluent quality.
PetKovac and Dr Korna H. Kocsis, FelsTisza - Vid Kezetvlmi Fels 4400 Nyiregyh, Szenyi u.19, Hungary, Tel. (36-42) 310 155, fax: (36-42) 310 713.