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Genanvendelse af gråt spildevand på campingpladser Summary and conclusionsGals Klint Camping Site is situated in the municipality of Middelfart on Western Funen, with direct access to the Little Belt. The site, which may be regarded as a typical Danish campsite, has served as an example for the selection of possible solutions for treatment of grey wastewater from campsites. Gals Klint Camping is suitable as basis for a pilot project, as the shower building on the site is prepared for greywater reuse for flushing the toilets. Furthermore, the water consumption in the period 1999 – 2000 has been registered and divided into water for toilets, water for washbasins and shower facilities and consumption for other purposes, thus providing a detailed basis for the evaluation of impacts, possible savings and seasonal variations. Firstly, a desk study was carried out in order to characterise grey wastewater from bathing facilities, i.e. washbasins and showers. The study was supplemented by an analysis of grey wastewater from Gals Klint Camping. The desk study and the grey wastewater analysis form the basis for the dimensional wastewater parameters, while the registration of the water consumption is based on the hydraulic dimension parameters. Dimensioning wastewater parameters.
A number of evaluation criteria have been listed on this background. The following criteria form the basis of the selection of possible concepts for recycling of greywater on campsites:
The evaluation criteria aim to select low-technological concepts with high operational reliability, minimum risk for obnoxious smells etc. and a minimization of operation and maintenance. However, the primary criterion is the health aspect, which is why a concept with a final disinfection is a requirement. Legislatively the cleaned greywater must by today’s standards have a purity degree equal to that of drinking water as stated in Regulation No. 515 of 29/8-1988: "Regulation on water quality and supervision of water supply plants". With the Action Plan to promote the encouragement of ecological wastewater treatment, the Danish Environmental Protection Agency has opened up for the use of other types of water for toilet flush including grey wastewater. The grey wastewater will be cleaned to the best possible quality with the chosen method, and the effectiveness of the process will be pinpointed by the execution of the common target program for Action Plan Projects on the reuse of grey wastewater (Phase 2-4 of the project). Based on the results from this and similar projects, The Danish Environmental Protection Agency will carry out a risk assessment and finally decide whether a law reform should be prepared in order to make legal the reuse of wastewater from bath and washbasin for toilet flush under closer defined conditions. The primary incentive for recirculation of greywater on campsites will be the economic benefit from water savings and to a smaller degree a possible environmental benefit. The Danish Camping Association has informed that the actual time for repayment of the investment of a greywater installation should normally not exceed approx. 6 years, since later repayment would make the investment less attractive for the owners of the campsites. Based on the desk study, a number of concepts for treatment of grey wastewater are examined. Methods for cleaning grey wastewater.
Based on the installations described in literature and on the suppliers’ proposals, the following three concepts, all with final disinfection, were chosen for a further evaluation:
Upon a thorough investigation of the concepts, it is estimated that all three solutions are suitable for the treatment and reuse of grey wastewater. As starting point for the establishment of a pilot project at Gals Klint Camping the biological sand filter is chosen. Outline of the pilot project The greywater installation consists of several units:
The installation is adjusted to obtain a high degree of operational reliability, an effective disinfection, a low risk of odour impact etc. Furthermore, the wish to make the installation profitable within a period of approx. 6 years has been given much emphasis. The cost of establishing a pilot project is estimated at approx. DKK 160,000.-, excl. VAT. The annual operational costs are expected to amount to approx. DKK 5,000 – 6,000 or an expected approx. DKK 5.-/m3 treated and recycled grey wastewater. An expected reduction of approx. 95% of the water consumption for toilet flush will result in a potential savings of approx. DKK 28,100.-/year, based on the average water price in Denmark. If the potential savings are related to the establishing and operational costs, this will result in an actual depreciation period for the pilot project at Gals Klint Camping of approx. 9 – 10 years. The above direct depreciation period is thus approx. 4 year longer than the average period normally accepted at Danish campsites. Regarding the variations in the country, approx. 15% of all municipalities in 2001 will have a depreciation period of 6 years or less. Furthermore, it can be concluded that the pilot project will be profitable in approx. 7 years or less in approx. 34% of the municipalities. With a view to a likely rise in the water tariffs in the future, and an increased investment to meet the demands for improved wastewater treatment in the open country, it must be expected that the future holds good possibilities for the profitability of treatment and reuse of grey wastewater at many Danish campsites.
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