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Summary and conclusionsIntroduction and Objectives Reclaimed water defined as storm water, greywater, water from industrial processes and water discharges from remediation pumping can be used as a water resource in the industry. For some industrial purposes the recovered water does not need to comply with the drinking-water quality requirements usually applied. The present project completed within "Aktionsplan for fremme af økologisk byfornyelse og spildevandsrensning" (Action Plan for Urban Development and Wastewater Treatment) comprises an evaluation of potential sources for production and reuse of "reclaimed water" in industry. According to the "Project document" describing the scope of work, the objectives of the project are the following:
Screening of Reclaimed Water Sources and Areas of Reuse/Recovery Water consumption, wastewater discharge and specific areas of water use within industry were evaluated based on old data originating from a survey from 1993-94, which is reported in /1/. It was concluded that the total water consumption by industry was 165 million m³ per year and the discharge of wastewater was 147 million m³ per year. The difference due to the method of data compilation. The survey concluded that the major areas of industrial water consumption were the following:
Water directly introduced to the "product" only comprised 2% of the total consumption. The use of reclaimed water was not included in the survey and can consequently not be evaluated. An additional survey has been conducted under the present project comprising an evaluation of approximately 320 large-scale industries' "Green Accounts" for year 2000-01. Table A below summarises the use water by industry based on information from the "Green Accounts". The source of data is the database operated by the Danish Commerce and Companies Agency named "WWW.Publi-com.dk"/13/. The table indicates that "Sea water" is the largest water source in the categories of "Power and Heating plants" and "Vegetable and Meat Processing Industry" (generally named Food Processing Industry). Furthermore, it is concluded that approximately 37% of the water consumption originates from public or private water supply, meaning that the water has drinking-water quality. Table A: Overview – Industrial Water Consumption in 2000-01, 320 large-scale industries From the table it can also be concluded that use of "Reclaimed water" only contributes with 0.2% of the total industrial water consumption. However, it is evaluated that the data source (Green Accounts) is incomplete, due to the fact that some industries only provide information regarding total water consumption and do not give information about the water source. It is anticipated that more accurate information from a new survey would not change the conclusion that the reuse of reclaimed water by industry is limited. The potential of discharges from remediation pumping comprising polluted water from groundwater pumping is based on a survey conducted by "Amternes Videncenter for Jordforurening" (The County Authority's Knowledge Centre for Soil Pollution) in 1996-97. Based on the results from this survey it is concluded that the total "Discharge from Remediation Pumping" was approximately 5.4 million m³ in 1997. Approximately 70% originated from the County of Copenhagen and only 8% was reused as second quality water. The remaining part was either discharged into public sewers or to the environment (river, lakes or sea). It is evaluated that reuse of reclaimed storm water, process water and ground water cannot be used in production or added to manufactured goods during processing. Reuse of reclaimed water must be limited to purposes where the water is not directly in contact with the product, otherwise the risk of product contamination or the impact on the manufactured goods is simply too high. Introducing the reclaimed water in the production process, for example as washing or flushing water, may have a serious impact on the quality of the manufactured goods. The economic benefit of using reclaimed water instead of water from deep wells is often limited and the risk can be high. Consequently, comprehensive risk assessment should be conducted before it is decided to use reclaimed water in the production process. Reuse of reclaimed water might cause problems with approval from relevant authorities namely The Factories Inspectorate and The Danish Veterinary and Food Administration (Food Inspection). Accordingly, the present project proposes reuse of reclaimed water outside the production process. Detailed Study of Pilot Installations Pilot studies have been conducted on the following three Danish installations:
T table below summarises the water consumption, the water discharge and the reuse of reclaimed water in 2001-02. Table B: Key Water Data from Danisco sugar's, Novozymes A/S's and CP Kelco's Green Accounts, 2001-02
Reclaimed Water Sources and Areas of Reuse Firstly the present water consumption, water usage and discharges was examined at process unit level at each factory. Secondly the present sources and new potential sources of reclaimed wastewater were identified. The results comprising reclaimed water sources and potential areas for reuse are summarised in the table below. Table C: Reclaimed Water Sources and Reuse Areas at Danisco Sugar, CP Kelco, and Novozymes A/S
Note: Identified Risks of Reusing Reclaimed Water An overall risk assessment related to the reuse of reclaimed water should comprise the following main areas:
An overall risk assessment has been conducted at each participating installation. The results are summarised in the table overleaf. Table D: Summarised Risk Assessment at Danisco Sugar, Novozymes A/S and CP Kelco
Economic Evaluation of Reclaimed Systems Key economic data comprising investment costs, net savings and payback period are summarised in the table overleaf. Table E: Summarised Investment Costs, Net Savings and Payback Period for Reclaimed Water System Projects
Note: (1) Exclusive of compensation DKK 400,000. Contract Agreements between Producer and Receiver of Reclaimed Water The contract conditions relating to delivery and receipt of reclaimed water can be revealed through consideration of the following issues:
If reclaimed water is exchanged between two parties (eg. a private company and public authority or between two private companies) it is recommended to sign a written Contract Agreement between the two parties. The Contract Agreement can be based on the draft standard form in Annex D, named "Forslag til standardaftale – Levering af sekundavand". (Draft Standard Agreement between Producer and Receiver of Reclaimed Water). Conclusions and Recommendations The present project has identified possible supply sources of reclaimed water within the following industry categories:
Use of reclaimed water is proposed in the following areas of the industrial production process:
An overall risk assessment related to the reuse of reclaimed water should comprise the following main areas:
Reuse of reclaimed water can have consequences for occupational health and safety as well as the environment, e.g. wastewater discharges, air emissions and solid waste disposal. These consequences must be carefully evaluated under each project. Technical issues should include assessments of how reserve water supplies (deep well or public/private water supply) should be maintained as emergency supplies. Necessary permits or exemption possibilities to use other supplies should be organised to cover the event of failure in normal supplies or if the quality of the reclaimed water does not comply with required quality. Reliable emergency supply must be available at short notice securing production failure and any loss of income as a result of supply failure. Previous research studies /2/ have indicated that a yearly volume of minimum 50,000 m³/year must be available before a project becomes economically feasible. The economic evaluation conducted under the present project indicates that the reclaimed water must replace drinking water, which is bought outside the company and that a water tariff of more than DKK 5-10 /m³ must be paid before a project is feasible. The economic evaluation of reclaimed water systems has verified that projects where reclaimed water substitutes non-drinking water from sources like the sea, lakes or rivers are not feasible because of low production costs (< DKK 1 /m³). Catalogue of Possible Project Areas for Reclaimed Water Systems Finally a catalogue of areas and industry categories with potential of introducing reclaimed water systems has been prepared. The list is summarised in the table overleaf. Table F: Catalogue of Possible Project Areas for Reclaimed Water Systems
A list of 17 industries with either potential for production or reuse of reclaimed water has been prepared. The list, which comprises relevant pilot-project installations, appears in chapter 3.6.2 of the present report. However it should be noted that the funds under "Aktionsplanen for fremme af økologisk byfornyelse og spildevandsrensning" (Action Plan for Urban Development and Wastewater Treatment) for conducting such studies are not available in the 2004 budget allocation.
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