Application of HACCP principles in drinking water treatment

Transcription

1 Desalination 210 (2007) Application of HACCP principles in drinking water treatment I. Damikouka a *, A. Katsiri b, C. Tzia c a National School of Public Health, Department of Sanitary Engineering and Environmental Health, Athens, Greece Tel. +30 (210) ; Fax+30 (210) ; skoyz2002@yahoo.gr b School of Civil Engineering, c School of Chemical Engineering,National Technical University of Athens, Greece Received 30 November 2005; revised 13 April 2006; accepted 11 May 2006 Abstract One of the most important tasks at any water treatment plant is safeguarding the quality of drinking water. Worldwide, the drinking-water sector is increasingly aware of the limitations of end-product testing for ensuring safety. One limitation is the steady increase in the number of potentially occurring pathogens and chemicals that need to be monitored. A further limitation is the delayed availability of results in relation to the timing of interventions needed to maintain the safety of a supply. Ensuring the safety of a supply requires monitoring not only of the finished drinking-water, but particularly of parameters which indicate whether the key control measures in a given process are functioning correctly. Preventative measures have therefore become very important. The Hazard Analysis Critical Control Points system (HACCP) is a food safety management system which uses the approach of controlling critical points in food and drink production, and the framework of its concept consists of 7 principles. According to the Council Directive 93/43/EEC and the recent Regulation (EC) No 852/2004 on the hygiene of foodstuffs, the application of HACCP in food production is obligatory. In the present work, the HACCP principles were applied to the Aspropyrgos Water Treatment Plant. The critical control points identified include filtration and chemical disinfection. Keywords: HACCP; Drinking water *Corresponding author. 1. Introduction Drinking water may be produced from a variety of sources, for instance, surface or groundwater. The qualitative characteristics of drinking water are described in the Council Directive 98/ 83/EC on the Quality of Water intended for human consumption [1]. This specifies that water should be free from any substances constituting a Presented at the 9th Environmental Science and Technology Symposium, September 1 3, 2005, Rhodes, Greece. Organized by the Global NEST organization and prepared with the editorial help of the University of Aegean, Mytilene, Greece and the University of Salerno, Fisciano (SA), Italy /07/$ See front matter 2007 Published by Elsevier B.V. doi: /j.desal

2 I. Damikouka et al. / Desalination 210 (2007) potential danger to human health and should be aesthetically acceptable. Drinking water should not contain any microorganisms known to be pathogenic capable of causing disease or any bacteria indicative of faecal pollution [2]. Major groups of interest include bacteria (total coliforms, Escherichia coli, Salmonella, Shigella, Yersinia, Vibrio), viruses (hepatitis A, enteric viruses), algae, fungi, protozoa (Giardia lamblia, Entamoeba histolytica, Crypto-sporidium parvum) and worms. As far as the inorganic and organic contaminants are concerned the most important with regard to health are heavy metals (arsenic, lead, chromium, mercury, cadmium, etc.), turbidity, organochlorine and organophosphorus pesticides, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and disinfection byproducts [2]. Each type of raw water has a characteristic pollution pattern, and treatment must be related to the source water quality and the desired end product standards [3,4]. A conventional water treatment plant as the one depicted in Fig. 1 consists of the following steps/ procedures: screening, coagulation, flocculation, sedimentation, clarification, filtration and disinfection. In order to be able to achieve the quality goals on the basis of legal requirements, the water treatment plants already carry out comprehensive quality control, which involves periodic tests of samples, in combination with various on-line measurements [5]. A process technical control of possible risks and the monitoring of critical points provide a solution for preventing the occurrence of quality or safety defects. Such a procedure for the determination of hazards and for their avoidance is presented by the HACCP method. In principle, it involves the control of the processes and signals a shift in emphasis from resource-intensive end product inspection and testing to preventive control of hazards at all stages of food pro- Fig. 1. Process flow diagram for Aspropyrgos Water Treatment Plant.

3 140 I. Damikouka et al. / Desalination 210 (2007) duction. HACCP is a tool to assess hazards and establish control systems that focus on prevention rather than relying mainly on end-product testing [6]. The HACCP system was developed in the 1970s as a universal, scientifically based framework to assure safe food production. It has been expanded and improved since then and has now become a universally accepted system which is increasingly being used by food producers, regulatory authorities and inspection services alike. An internationally valid explanation of the HACCP concept has been laid down by the FAO/ WHO Codex Alimentarius Commission in an annex to its General Principles of Food Hygiene [6 8]. According to this, the HACCP concept is a system for the identification, evaluation and control of significant health hazards from food. Thus, specific health hazards (of chemical, physical and microbiological origin) for the consumer should be identified and the probability and significance of their occurrence assessed. In general, HACCP aims to eliminate influences that result in food borne diseases in humans from the production, handling, treatment, transportation and storage of foods. According to the Council Directive 93/43/EEC [9] and the recent Regulation (EC) No 852/2004 [10] on the hygiene of foodstuffs, the application of HACCP in food production is obligatory. The HACCP system is a useful framework. However, as presently used in food microbiology, the system is mainly qualitative and may be subjective, because the opinions of experts are relied upon when defining critical limits for CCPs. In order to make the assessment of drinking water supply more objective, QRA (Quantitative Risk Assessment) has been employed [11]. HACCP is in its infancy for the water industry. The identification of hazards and key control measures dealing with hazards is applied as part of standard good water supply practice. What is not applied generally is the discipline of the formal HACCP procedure [5]. However, adoption of the approach of HACCP in the field of drinking water has begun in Australia and France. HACCP adds value by providing a structured approach to risk assessment and by focusing management and operatives attention on the key control measures. In the present work, the method of HACCP and its 7 general principles, the necessary legislation for drinking water, the microbiological and chemical parameters as well as the essential steps of treatment for the production of drinking water are examined. The HACCP principles were applied to the Aspropyrgos Water Treatment Plant. This analysis started with the identification and evaluation of significant health hazards of water from the catchment area, treatment processes, storage, distribution to the consumer s tap and resulted in the construction of the HACCP plan (principles 1 5) for the production of drinking water for this particular plant. 2. Materials and methods The proper identification of CCPs is a key issue in HACCP, because the major efforts in process control will be directed towards these steps. Surface water is subject to a diversity of pollutants and it is necessary to control the extent to which this occurs. For the practical application of the HACCP concept according to Codex Alimentarius [6], 7 rules have to be followed which are laid down in 7 main principles and constitute the basis for the establishment of a HACCP plan [8,12]. Principle 1: Perform a hazard analysis The objective of this step is to obtain a comprehensive list of all biological, chemical and physical agents or conditions which have the potential to cause harm, the assessment and the severity of the risk associated with these hazards as well as the possible control measures for each hazard. Principle 2: Determine the Critical Control Points (CCPs): Codex describes a CCP as: A step at which control can be applied and is es-

4 I. Damikouka et al. / Desalination 210 (2007) sential to prevent or eliminate a food safety hazard or reduce it to an acceptable level. The intent of the HACCP system is to focus control at CCPs. Principle 3: Establish one or several critical limit(s) Principle 4: Establish a CCP monitoring system Principle 5: Establish corrective action to be taken if monitoring indicates that a specific CCP is no longer under control Principle 6: Establish procedures of verification to confirm a successful working of the HACCP system Principle 7: Introduce a documentation system taking into account all processes and records in accordance with the principles and their application Furthermore, there are 5 preparatory steps in the application of HACCP which are: Step 1: the assembly of the HACCP team Step 2: the description of the product Step 3: identification of its intended use Steps 4 and 5: the construction and confirmation of a flow diagram. This makes documentation more accessible and makes it easier to introduce changes. The application of preparatory activities and the principles of HACCP resulted in the HACCP plan, part of which, is described in Table 3. The CCPs are determined going through the decision tree of the method [7,12]. The conceptual approach is shown in Fig. 2. Codex provides this decision tree to assist with a logical procedure for this but the use of this decision tree is not mandatory [6]. The created HACCP plan (principles 1 5) could be used as a supplementary system in the factory, if the treatment plant intends to implement HACCP as a working system. The HACCP plan includes the process steps of the treatment, the identified hazards, the preventative measures, the determined critical control points, a monitoring system, the critical limits of CCPs monitoring parameters as well as the necessary corrective actions. Critical limits have been set according to legislation (The Council Directive on the Quality of Surface Water intended for the abstraction of drinking water 75/440/EEC [13] and the Current Drinking Water Directive 98/83/EC [1]), operating procedures and performance targets of the plant. 3. Results and discussion In hazard analysis emphasis was given to events, incidents or situations that could lead to hazards being introduced into or not being removed from the water [5]. Risk assessment is the key to the entire process -identifying risks, assessing their significance and the controls in the system that manage those risks in a systematic fashion- starting from the catchment and working down. A flow diagram of the Aspropyrgos Water Treatment Plant was drawn up as depicted in Fig. 1 [14]. At each step in the process, the potential hazard to water quality and the controls to prevent the hazard entering the water were identified [15]. A semi-qualitative risk assessment of Aspropyrgos Water Treatment Plant was applied and a simplified example is given in Table 1. It is noted that the water treatment plant is not responsible for the quality of water coming from the catchment area. The CCPs are determined going through the decision tree of the method [15]. The conceptual approach is shown in Fig. 2. An application of the CCP decision tree on the catchment area and the post-chlorination process is depicted in Table 2. The application of preparatory activities and the principles of HACCP resulted in the HACCP plan, part of which is described in Table 3 [15]. The HACCP plan includes the process steps of the treatment, the identified hazards, the preventative measures, the determined critical control points, a monitoring system, the critical limits of

5 142 I. Damikouka et al. / Desalination 210 (2007) Fig. 2. The CCP decision tree. CCPs monitoring parameters as well as the necessary corrective actions. In this case only the CCPs are examined. The catchment area, Mornos Lake, is itself considered a CCP, in spite of the existence of preventative measures, for those microbiological and chemical hazards which the plant cannot manage [15]. During the pre-chlorination procedure, optimization of the dose of chlorine is necessary so as to avoid the formation of THM s, without affecting the disinfectant efficiency. This is achieved when trace levels of residual chlorine are present at the filters outlet. Filtration is a CCP, because it is the last step for the removal of inorganic sub-

6 I. Damikouka et al. / Desalination 210 (2007) Table 1 Example of risk assessment hazards from catchments Bacteria, viruses, protozoa Controls in catchment Risk Controls in water supply system Residual risk E.g. security of protected catchments High (likelyhood and consequence) Coagulation/ filtration (CCP) disinfection (CCP) Must be acceptable prior to consumption Table 2 Application of CCP decision tree Process step Hazard Q1 Q2 Q3 Q4 CCP Catchment area Yes No Yes No Yes Post-chlorination Yes Yes Yes stances and small flocs, and since efficient filtration is dependent upon the procedures which precede it, in assessing the efficiency of the filtration process it is requisite/ desirable that the turbidity at the sedimentation tank outlet be no greater than 1.5 NTU and at the filters outlet no greater than 0.2 NTU. Post-chlorination is the last step for the elimination of microorganisms and is a preventative measure against recontamination in the distribution network. The storage of treated water and the distribution system are CCPs due to the risk of recontamination and regrowth. Recontamination must be prevented by adequate construction, by maintaining positive hydrostatic pressure at all times and by hygiene precautions due to the possibility of chemical and microbiological recontamination. During treatment and storage, there are many on-line sensors with remote monitoring in a control room working continuously. 4. Conclusions The HACCP system provides a mechanism for ensuring that the appropriate corrective action is taken in the event of any failure. This could range from simple spot dosing to providing alternative supplies and public notification, depending on the event. The structured approach of HACCP to analyzing hazards provides a means of assessing the existing barriers to contamination and improving upon their operation. In relation to the Aspropyrgos Water Treatment Plant, there is no need to introduce new infrastructure (e.g. treatment), but rather a number of procedural improvements could be implemented. The most important CCPs identified are flocculation, filtration and chlorination. The created HACCP plan could be used as a supplementary system by the factory, if the treatment plant intends to implement it as a working system. The process of preparing a HACCP plan in itself highlights possible areas for improvement, which could be addressed, whether or not the entire HACCP plan is enforced. References [1] Council Directive 98/83/EC on the Quality of Water intended for human consumption. [2] WHO, Guidelines for Drinking-water Quality, 3rd ed., WHO, Geneva, [3] WHO, Guidelines for Drinking-water Quality, 2nd ed., WHO, Geneva, 1993.

7 144 I. Damikouka et al. / Desalination 210 (2007) Table 3 Principles of HACCP applied to Water Treatment Plant in Aspropyrgos Process step Hazards Preventive measures CCP parameters/ limits Monitoring procedure Corrective actions Catchment area (Mornos Lake) Algae growth, pathogens, bacteria, viruses, protozoa Chemical Heavy metals, pesticides, PAHs, PCBs, solvents, fertilizers Pre-chlorination Chemical Overdose, formation of disinfection by-products (THMs) Coagulation/ flocculation/ sedimentation Viruses, protozoan oocysts Chemical Poor floc formation and removal of inorganic substances Filtration Chemical Inorganic constituents, filter defects Post-chlorination Storage of treated water Distribution Survival of pathogens Chemical Overdose, formation of THMs Recontamination Regrowth, re-contamination Define protection zone- Acute toxicity detectors Define protection zone- Acute toxicity detectors Optimize dose and contact time of disinfectant Optimizing coagulant, coagulant-aid dose and mixing conditions Optimizing coagulant, coagulant-aid dose and mixing conditions Regular backwashing and cleaning In accordance with 75/440/EEC In accordance with 75/440/EEC Chlorine dose 1,8-2,5ppm Trace levels of residual chlorine at filters outlet Turbidity < 1-1,5 NTU at sedimentation tank outlet Faecal index bacteria Specific pathogens turbidity Increase treatment, alternative supply Frequent chemical analysis Increase treatment, use of PAC, alternative supply Measurement of flow On-line residual chlorine at filters outlet On-line measurements of turbidity and ph Turbidity < 1-1,5 NTU On-line measurements of turbidity and ph Turbidity < 0,2 NTU at filters outlet Particle counts Pressure loss Optimize dose and contact time Residual concentration of chlorine: ,6ppm Bacteriological indicator organisms Post chlorination Changes of coagulant dose and mixing conditions or even ph Increase disinfection Changes of coagulant dose and mixing conditions or even ph On-line measurements Optimization of coagulation/ sedimentation procedure On-line monitoring Emergency chlorination after storage tank Careful chlorination THMs < 100µg/l Frequent analysis Change of dose Dilution Integrity of tank construction. Air filtration Reduce residence time Positive pressure. Reduce biofilm potential. Residual chlorine, replacement and flushing programs Chemical Reduce residence time Integrity of pipe construction Replacement Total coliforms Residual chlorine Height of water Total coliforms Pressure in system POPER >1bar In accordance with 98/83/EEC In accordance with 98/83/EEC Daily analysis of index bacteria Isolate reservoir Rechlorination Inspection Rechlorination-Isolate part of system Chemical analysis Isolate part of system Replacement

8 I. Damikouka et al. / Desalination 210 (2007) [4] American Water Works Association, Water Quality and Treatment, A Handbook of Community Water Supplies, 4th ed., McGraw-Hill, Inc., USA, [5] Umweltbundesamt, Federal Environmental Agency, Water Safety, Conference Abstracts, Berlin, April [6] FAO/ WHO Codex Alimentarius Commission, Hazard Analysis and Critical Control Point (HACCP) System and Guidelines for its Application, Annex to the Recommended International Code of Practice General Principle of Food Hygiene, CAC/RCP , Rev. 3, [7] D.A. Corlett, Jr., HACCP User s Manual, Aspen Publication, Maryland,1998. [8] S. Mortimore and C. Wallace, HACCP, A Practical Approach, Chapman & Hall, [9] Council Directive 93/43/EEC on the Hygiene of Foodstuff, Official Journal of the European Communities, July 19, [10] Regulation (EC) No 852/2004 of the European Parliament and of the Council of 29 April 2004 on the Hygiene of Foodstuffs. [11] A.H. Havelaar, Application of HACCP to drinking water supply, Food Control, 5(3) (1994) [12] C. Tzia and A. Tsiapouris, Application of the Hazard Analysis Critical Control Point (HACCP) System in the Food Industry, Papasotiriou, Athens, 1996, (in Greek). [13] Council Directive 75/440/EEC on the Quality of Surface Water Intended for the Abstraction of Drinking Water. [14] Operational booklet of Aspropyrgos Water Treatment Plan, (in Greek). [15] I. Damikouka, Postgraduate Diploma Thesis: Application of HACCP principles in drinking water treatment, NTUA, Athens, 2004, (in Greek).