214.314 – Assignment 1 Marking Schedule
Table of Contents
A. Water Information New Zealand database (WINZ)
B. Waikanae Water Treatment Plant (WWTP)
1. WINZ information and codes of WWTP
Characteristics and Potential Source for Contamination
Catchment of Surface Water Protozoan Risk Category
3. Treatment Process
1) Raw Water
2) Activated Carbon Dosing
3) Rapid Mixer
5) Sand Filters
6) Addition of Ultraviolet (UV) Light, Chlorine, Fluoride and Lime
7) Clearwater Tank
8) Sludge Treatment
4. Plant Hazard Identification
5. Drinking-Water Standards for New Zealand 2005 (revised 2008)
Maximum Acceptable Values (MAVs)
Compliance Criteria and Transgressions
Waikanae Water Treatment Plant
6. Water Safety Plans
7. Treatment Plant Maintenance and Management
Appendix 1: WINZ 7
Appendix 2: WINZ 6
Appendix 3: Checklist for Water Treatment Plant Visits
Appendix 4: Waikanae River
Appendix 5: Waikanae Water Treatment Diagram
Appendix 6: Catchment
Appendix 7: Activated Carbon Dosing (Hopper Chamber)
Appendix 8: Rapid Mixer
Appendix 9: Alum Feeds
Appendix 10: Polyelectrolyte Feeds
Appendix 11: Flocculation
Appendix 12: Clarifier
Appendix 13: Sand Filters
Appendix 14: Ultraviolet Light Disinfection System
Appendix 15: Chloride, pH, and Turbidity Monitoring
Appendix 16: Fluoride Monitoring
Appendix 17: Dosing of Chloride, Fluoride, and Lime
Appendix 18: Clear Water Plant and Tanks
Pumps and Pipes for Distribution
Appendix 19: Sludge Treatment
Appendix 20: Health and Safety Sign (HAZCHEM)
Appendix 21: Health and Safety Induction Form
Appendix 22: Supervisory Control and Data Acquisition (SCADA) Schematics*
Imagine a world where access to water is limited. Needless to say access to a clean and safe water supply used for bathing, cooking, drinking, and washing. It is almost upsetting to think of the consequences of this scenario in real life especially in the 21st century. Looking back at the daily conditions in previous centuries, most households have to rely on a nearby catchment like a lake, a river, or a spring. People who have access to any man-made watersheds and water channels were probably considered as more fortunate. During the time of the ancient Romans, from the conception of its republic to the downfall of its empire, aqueducts were a technological marvel that immortalised the ingenuity and engineering skills of the ancient Romans. Aqueducts not only brought ancient Rome the status it deserved but it also improved hygiene and sanitation that eventually improved human health conditions. Access to clean water has truly become a basic necessity that helped shape the development of human civilization.
Nonetheless, back then modern plumbing was non-existent and uncommon that people still need to fetch and carry water back to their homes. At present, majority of us often take water for granted without thinking how much effort and work were spent in order for us to enjoy a glass of clean and drinkable water from the tap; or to wash our hands whenever we go to the toilet; or to take baths directly in our homes. Though, there are still places in the world where water is inaccessible in households, the point is that the evolution in the accessibility of water had brought a revolution that kick-started the growth for building sustainable communities. This present period in our history, where litres upon litres of water is already within our grasp even without performing a toilsome effort in our part as the consumers. Since people consume water for their daily needs, it has become highly imperative to ensure that the quality of drinking water is safe for consumption, and most importantly had been regularly assessed by a regulatory health body.
Water safety is above all else crucial in the collection, distribution, and consumption of drinking water especially in developed nations including New Zealand. First and foremost, drinkable water is protected in New Zealand under the Resource Management Act 1991 and Health (Drinking Water) Amendment Act 2007. Whereupon section 14 of the Resource Management Act 1991 underpins the restrictions relating to water sources, and under section 43 of the same Act underpins the need for compliance under a National Environmental Standards (NES). Secondly, the assessment and treatment of drinking water needs to comply with the Drinking Water Standards for New Zealand (DWSNZ) before the water can be transported to the public. In summary, the DWSNZ contains water safety plans (originally known as Public Health Risk Management Plans, or PHRMPs until 2013) as a guide for safe management of water supplies (Ministry of Health, 2008). Water safety plans upholds the use of risk-management principles during treatment and distribution in order to reduce the risk for any contamination.
This report shall provide information on the Drinking Water Database used in New Zealand, and examine the Waikanae Water Treatment Plant which shall include: its catchment, treatment process, hazard identification, and an evaluation of the plant protocols in line with the Drinking-water Standards for New Zealand 2005 (revised 2008) including the water safety plans.
The Water Information New Zealand (WINZ) is an online database which was created by the Environmental Science and Research (ESR) for the Ministry of Health (MoH) (Water Information New Zealand, 2017). The main goal of WINZ is to monitor the protection of drinking-water processes, and at the same time provides a current source of a national water supply info involved in drinking-water quality management, which includes:
- the components of the water supplies;
- compliance with the current DWSNZ; and
- Public health grading of supplies (now only done voluntarily or upon request as of 2017).
It fundamentally have the information relating to all the drinking-water supplies, water carriers, and recognised laboratories in New Zealand. Since ESR maintains the database, software updates are also distributed by its Water Information Systems group to the water suppliers, district health boards (DHB), and any other groups that have access to WINZ (Water Information New Zealand, 2017).
In addition, WINZ can analyse the monitored data and provide a suggested sampling schedule for the supply. Once the appropriate information is readily available, the water supplier can store it in the database which will determine the compliance status of the supply. In essence, transgressions (for example a non-compliance in the microbiological quality of drinking-water) and its corresponding corrective actions are generated by the database.
All district health boards, who have access to WINZ, uses the same version of software with their water suppliers, but with some extra features. The DHBs obtain information from all water supplies in their district, while the suppliers solely have information to their own respective water supplies. Further, DHBs collect compliance information from the water suppliers which will eventually be uploaded in the drinking-water database.
As mentioned if there are transgressions, WINZ also reports the Annual Review of the NZ Drinking-Water Quality which gives information regarding the breach committed by the water supplies and the actions undertaken. The purpose is to assess the national compliance of registered water suppliers with the current DWSNZ. This establishes the practice of improving public health by mitigating the exposure to water-borne diseases and contaminations listed under Priority Classes for Drinking-Water in the DWSNZ 2005 (revised 2008). Furthermore, there are two versions of WINZ that are available:
- WINZ 7 (refer to Appendix 1), which is a Microsoft operating system used for monitoring & scheduling sample entry. It also evaluates the compliance with the DWSNZ 2005 (revised 2008).
- WINZ 6 (refer to Appendix 2), which is an internet-based system for the annual survey of drinking-water quality in the country. Its initial mission is to present the Ministry of Health with database apps to oversee the Drinking-Water Assistant Programme (DWAP).
(Water Information New Zealand, 2017)
In addition, as of January 2017, a newly web version of WINZ is nearly in completion which would ideally combine all the features and functions of the two said versions (Water Information New Zealand, 2017).
The following table is a summary of the processes and WINZ codes associated with the Waikanae Water Treatment Plant taken from the WINZ website.
|Community||Waikanae, Paraparaumu, Raumati|
|Name of the Supplier||Kāpiti Coast District Council|
|Name of the Local Authority||Kāpiti Coast District Council|
|Name of the Public Health Provider||Hutt Valley Public Health Service|
|Distribution Zone Details|
|Treatment Plant Details|
|Name of the Treatment Plant (TP)||Waikanae Water Treatment Plant|
|Treatment Plant Code||TP00206|
|Name of Source||Source Code|
|Bores (normally used for recharging)
K4 – Cooper 1
K5 – Nga Manu
K6 – Wooden Bridge
Kb4 – Landfill
K10 – Market Garden
K13 – Huiawa
|Number of sources supplying the WWTP||1|
|Standards Used||DWSNZ 2005 (revised 2008)|
Fluoride (below MAV)
|Public Health Grade* of the source and TP
*now only done voluntarily or upon request
Also refer to Appendix 3 for a copy of the Checklists used to evaluate the Waikanae Water Treatment Plant.
The Waikanae Water Treatment Plant, which is located in the Kāpiti Coast District, was commissioned in 1977 to supply safe potable water to the township of Waikanae, Paraparaumu, and Raumati (Kāpiti Coast District Council, 2015). Its primary source is from the Waikanae River catchment, which covers an area of 124.8 km2 (see Appendix 4). The river is capable of producing 34,000 m3/day or 34 million litres per day. Nevertheless, under the resource consent enforced by the Kāpiti Coast District Council, the treatment plant is only allowed to take between 23,000-30,400 m3/day (23-30.4 million litres per day). On an average day, the plant treats 14 million litres of water per day. When water levels are low, supplementary water is provided from groundwater bores which is used to recharge the river. According to Bassett (n.d.), Iron (Fe2+) and Manganese (Mn2+) were tested for water quality and have indicated an exceedance within the allowable value of the DWSNZ. The WWTP added an extra stage to mitigate the breach to an acceptable level.
Further, the catchment is nearby pastoral lands with some areas remaining in native bush. The ground surface and slope of the river is steep and has many levels due to practical reasons under the resource consent. One is to allow the fish and other aquatic life to move upstream and breed, which have the purpose of keeping the river healthy. Another is to minimise the turbidity of collected water, including mud and other sediments, which is caused by the rapid rise of water levels during heavy rainfall. Speaking of rainfalls, water collection is still in progress during stormy days but the collection process is decreased due to the difficult filtration and time-consuming treatment.
The protozoal risk category log credit of the water source, based from the unofficial evaluation done during the visit, is 3. However, due to the presence of a small pastoral activity that have a low concentration of cattle, horses, sheep, or human within the vicinity of the catchment, therefore, the log credit is moved at 4 which is more appropriate. Refer to the figure below for a satellite image of the WWTP and the Catchment.
Figure 1. Satellite Image of the Water Treatment Plant, Waikanae River, and nearby potential contamination sites (retrieved from Google Earth, 2017).
For a summarized diagram of the Waikanae Water Treatment Plant, refer to Appendix 5 of this report.
As mentioned above, the treatment plant uses raw surface water from the river. It is pumped using two (2) big pumps: Kelly and Lewis type 2403H Berkeley vertical turbines (Refer to Appendix 6). Additionally, the pumps are capable of drawing 400 L/s of water. Additionally, the water pH from the river is slightly acidic which can lead to corrosion of the metal pipes and fittings. This corrosion reduces the efficiency of the chemicals used to treat the water. As a result lime (calcium hydroxide, Ca(OH)2), which has an alkaline or basic property, is extensively used to balance the acidic pH of the river water in order to avoid these problems (Kāpiti Coast District Council, 2007).
The addition of Powdered Activated Carbon (PAC) to the treatment process is for managing the odour and taste of water from the river and the emergency bores (Bassett, n.d.). Aside from the already mentioned effects, PAC would also absorb and reduce the soluble organics such as algae present in the untreated water 1). The PAC particles have very large surface area that absorbs the toxins including Geosmin, a type of actinobacteria, which can only be detected at parts per billion. Refer to Appendix 7.
From the source, the water goes up to the rapid mix chambers where a series of sedimentation steps are being done, see Appendix 8. Below are the steps during this process:
- Chemicals such as Aluminium sulphate (alum) or Poly-aluminium chloride (PACl) is added thoroughly to neutralise the negative charge given off by suspended solids which gives the water a dirty look and taste. The treatment plant uses PACl more frequently, however, it is more expensive of the two. On the other hand, alum is normally used when the turbidity is very high. The neutralised solids are then clumped together, in a process called coagulation. See Appendix 9.
- During coagulation or flocculation, a polymer called flocculants (also called polyelectrolytes), which is a water-soluble clarifying agent, is added to aggregate colloids and other suspended particles, forming a floc. This procedure is called flocculation, and what is does is to launder the sediment from the water. Basically, the use of flocculants or flocking agents is to improve the sedimentation and filterability of small particles especially in water treatment. See Appendix 10 and 11.
- During the summer period, algae grow in the river. These algae produce toxins which can cause serious poisoning when consumed. As a result, the water treatment team developed a system to add powder activated carbon (PAC) to the water in the rapid mixer.
(Kāpiti Coast District Council, 2007)
After the particles are treated at the rapid mixer, it then proceeds to the next stage.
This is just an extension of the previous stage, it is essentially the actual sedimentation process. This means that the water, which entered the clarification tanks, allows the solid particles to settle to the bottom of the tanks. The suspended solids (dirt, mud, etc.) are removed from the water. The solids that settled to the bottom are withdrawn in order to be extensively processed to reduce the water content and pumped to the sludge treatment plant. The water from the top of the clarifier is pumped to the next stage. The water pH at this stage ranges from 6.5 to 8. See Appendix 12.
The water coming from the clarifier goes into the filtration channels where it gets evenly distributed into the four (4) dual media rapid sand filters (Kāpiti Coast District Council, 2007). The dual media is mainly comprised of anthracite (top layer) and graded sand (bottom layer). The water then passes through the medium and any remaining suspended solid are contained in the filter. Further, after the water had been strained by the dual media filters, about 99.99% of pathogens are removed. When the filter becomes clogged, water and air are run backwards through the filter to remove the particle making the obstruction. The backwash is then sent into the sewer. See Appendix 13.
Before the water from the previous stage goes to the Clearwater tank, the water passes through high intensity UV light (refer to Appendix 14) where any remaining pathogens are rendered harmless to the public and making the pathogens unable to reproduce. The quality of water is not changed during this process. Following the UV treatment, is the addition of chemicals that is purposely meant to stay in the water. The addition of these chemicals will be discussed below:
- Addition of Chlorine gas (Cl2( g))
Chlorine is added in the water to kill any pathogens which had survived the Filtration and UV Light treatment. Chlorine gas also disinfects the pipes and tanks against microbial growth. See Appendix 15.
- Addition of Fluoride (F–)
Fluoride is added for dental health. It is not compulsory but it is strongly suggested by the Ministry of Health. See Appendix 16.
- Addition of Lime (Ca(OH)2)
The addition of lime is for pH correction, the recommended pH should be at 7.8 to 8. This is maintained at a slightly high pH to keep the pipes and tanks from corroding. See Appendix 17.
(Kāpiti Coast District Council, 2007)
The drinking water is now fully treated and can confidently be evaluated fit for human consumption. It is readily available to be distributed to the reservoirs and supply the township of Paraparaumu, Raumati, and Waikanae. See Appendix 18.
Sludge or the waste product, removed from the bottom of the clarifier, enters the sludge thickener which functions in a similar manner to the clarifier. The majority of sediments settle to the bottom, leaving clearer water at the top. The thick water at the bottom is pumped to a centrifuge which rotates to remove water from the solids. The solids are disposed of at the landfill and the water is pumped to the waste water treatment plant. Moreover, the water from the top of the thickener is also thrusted to the waste water treatment plant (Kāpiti Coast District Council, 2007). See Appendix 19.
There are many potential hazards, which can cause serious harm to any person, in the Waikanae Water Treatment Facility if both the personnel and visitors are not cautious, and if the hazards are not being controlled properly. This is why as mentioned above in the Treatment Plant Maintenance and Management section, every process in the plant is being monitored through a systemised computer program in order to avoid the potentiality of a hazard in a high-risked facility like the Waikanae Water Treatment Plant. Consequently, the Plant management team and the Kāpiti Coast District Council requires any personnel and visitor to undergo a health and safety induction program before working and going for an educational tour around the facility. The significant hazards can be divided into four classifications: biological, chemical, natural, and physical hazards.
Firstly, the Water Treatment Plant is located near a river. Although the Waikanae River is an asset, it is also at the same time a hazard. It has the potential to flood parts of Waikanae and Otaihanga. Flood events cannot only damage properties, they also put human life at risk. According to the Greater Wellington Regional Council (2014), in 1955 a large flood extensively damaged houses on the floodplain. Flooding and land erosion in the river and the plant has been an identified potential hazard in the flood control scheme.
Secondly, New Zealand is prone to earthquakes. Even if the said plant is built on stable bedrocks, which makes it shake less during an earthquake, it is still a natural hazard to be reckoned with because it might change the ground levels and may also lead to the altering of ground levels in the river which may cause flooding.
Thirdly, physical hazards can be defined as the hazards relating to human and mechanical errors. It may be accidental or intentional, either way it can cause hazard which can lead to the loss of water supply and delayed water supply to the distribution zones. These include the rotating machinery which is fully automated at all times, and the deep tanks which have open surface.
The chemical hazard which is present at the plant and is enumerated in the health and safety induction form are as follows:
- Chlorine gas (Cl2(g)) – a poisonous and corrosive gas that can cause pulmonary oedema.
- Fluoride (F-) – a toxic chemical that can cause poisoning when ingested.
- Aluminium Sulphate (Al2(SO4)3) – It is mildly corrosive which can cause minor burns and skin irritation.
- Lime (Ca(OH)2) – It is mildly corrosive which can cause minor burns and skin irritation.
- Potassium Permanganate (KMnO4) – It is highly corrosive which can cause minor burns and skin irritation.
Lastly, this type of hazard includes contaminants, including bacteria, viruses, and harmful microorganisms. Majority of these contaminants are coming from the Sludge Treatment Plant.
Hazard Control and Management Plan
Below is the summary of hazard control from the health and safety induction form of the plant and the Waikanae River Environmental Strategy 2014.
|Hazards||Waikanae Water Treatment Plant Solutions|
|Biological||Do not handle the wastes from the Sludge Treatment Plant unless you have been trained and given authority to do so. Strictly Follow Site Rules.|
|Chemical||Have a HAZCHEM sign containing the information of chemicals and possible hazards it can cause, contact information and number of who to contact in case of an emergency. Also include the possible remedies or first aid actions that are applicable.|
|Natural||Follow the Site’s Code of Practice in case of emergency. Assemble in the assembly point area during an emergency.|
|Physical||Install handrails, barriers, and signage for protection. Always be attentive.|
Under section 69A of the Health Act (1956), drinking-water shall be monitored and should comply with the drinking-water standards. In addition, the Health (Drinking Water) Amendment Act (2007), which has added provisions to the Health Act, ensures that all water suppliers have the duty to ensure that their water is safe to drink (Ministry of Health, 2008). It also underpins for the appointment of drinking water assessors (DWAs). The function of the DWAs are set out in section 69ZL of the Act.
Some of the functions of the DWA includes:
- Assess drinking water suppliers as to whether the suppliers are complying with the Act, drinking water standards, and implementing water safety plans
- Notify non-compliances to designated officers and suppliers
- Ensure records and information are supplied to the director general
- Assess competence of those doing the sampling of raw or drinking water to: calibrate equipment used to treat or monitor raw or drinking water, and undertake any other task required to ensure compliance with the Act standards and a water safety plan
- Authorise competent persons to undertake tasks complying with this part of the Act, the Drinking-water standards and any water safety plan
- Verify and approve if adequate water safety plans
- Check and monitor complaints received that they have been recorded and addressed
- Provide specified information to the Director General
The DWSNZ have two further aspects. First is to provide criteria for ensuring that the monitoring of drinking-water quality is being carried out to a consistent standard. Second, to specify the remedial actions where the public health risk is identified in order for the supply to be managed when standards are breached. The water safety plan details the remedial actions specific to its supply (Ministry of Health, 2008).
Furthermore, there are three main themes of the DWSNZ:
- the Maximum Acceptable Values (MAVs) or water quality standards;
- the compliance criteria and reporting requirements; and
- Remedial actions.
Maximum Acceptable Values (MAVs)
The MAV of a determinand in drinking water signifies the concentration of a determinand in the water that is not considered to cause any significant risk to the health of the consumers. The MAVs in the DWSNZ define water that is suitable for human consumption and hygiene. Further, the MAVs, for most chemicals, have been calculated using a tolerable daily intake (TDI) method that identifies the dose below which no evidence exists that significant adverse effects will occur. There are two different MAVs for chemical and micro-organisms determinands, and both have different standards. The micro-organisms determinands uses a more appropriate parameter, which is the maximum indicator value (MIV). However for uniformity purposes, the term MAV is used throughout the DWSNZ (Study Guide, 2017, pp. 56-57).
Compliance Criteria and Transgressions
The compliance criteria is used for the assessment of chemical, microbiological, and radiological compliance which are specified in the DWSNZ. A transgression occurs when an event immediately threatens the safety of the consumer. Most transgressions are likely to result from inadequate control of a treatment process. It can be identified under the following indicators:
Priority 1 Determinands: Bacterial and Protozoal Contaminants
- The indicator for bacterial contaminants is the excessive concentrations of Escherichia coli (more than 10/100 ml), and Cryptosporidium and Giardia representing protozoal contaminants.
- E. coli must not be present in drinking-water leaving the treatment plant or the distribution zones. If detected, it should be followed up by a remedial action.
- For protozoal compliance, a risked-based criteria must be used. Securing the water source is the primary compliance for ensuring protozoal criteria. Inactivation is normally the process to remove protozoa in the water by using Chlorine. Although, the use of chlorination is only effective on Giardia and not on Cryptosporidium. A protozoa treatment log credit was developed for protozoa removal. All it does is to give a log value which can be applied in the treatment and assessment and to identify the level of risk from source of protozoa.
- Viruses are also an indicator. However, little information is available at this point to be able to determine a possible MAV. Although there is no available MAV for viruses, the presence of E. coli may also signal the presence of viral pathogens.
Priority 2 Determinands: Chemical Contaminants & Cyanotoxins
- Cyanotoxins at concentration sufficient to cause acute adverse health effects, metals and metalloids, and chemical by-products from the disinfection process are all indicators for P2 contamination.
- The treatment system’s inability to disinfect to the level necessary to achieve satisfactory disinfection, as well as the inability to provide adequate barrier to particles in the water also contributes to contamination.
- For preventing cyanotoxins, catchment control is necessary and is the best defense for algal bloom formation.
- Chemical compliance requires that they do not exceed their MAV.
Also, different procedures apply depending on whether a non-compliance results from:
- Exceedance of MAVs
- Excursions beyond the transgression limits specified for operational requirements
- Incorrect procedures (e.g. inadequate sampling, incorrect calibration of metering equipment, analyses not being carried out a recognised laboratory, etc.)
(Study Guide, 2017)
To put it simple, these are preventative procedure which should be taken in when a non-compliance or a transgression have occurred. As mentioned, different MAVs have different parameters which also applies to remedial actions. The remedial actions thus minimise uncertainty on the part of the supplier as to whether the supply is meeting the quality requirements, and what to do in case of things going wrong (Ministry of Health, 2008).
Waikanae Water Treatment Plant
In relation to the Waikanae Water Treatment Plant, it is subject to the full scope of the DWSNZ. As a registered Treatment Plant, it is recorded in the Register of Community Drinking-water Supplies in New Zealand. It includes how many population is being serviced by the Waikanae Water Treatment Plant as well as the codes of the zones being supplied. Starting from the collection of water, the catchment is being controlled from any potential hazards. As mentioned in the Catchment section, the water source is unprotected and is only a controlled water source which is why it has a log credit of 4. The catchment itself is already categorised as a Priority 2 determinand. Priority 2 determinand are determinands of public health significance in supply or distribution zone that are present at concentration that exceed 50 percent of the MAV, and for microorganisms that are also present at concentration that exceed the unacceptable risk levels (Study Guide, 2017, p. 54). From the assessment, Waikanae River has a 50/100 ml E. coli contamination, due to the nearby pastoral areas. According the DWSNZ, the MAV for E. coli is less than one in 100ml sample, this means that the MAV for the raw water from the source is breached and therefore it is a Priority 2 determinand.
Moving on to the Rapid Mixer and Clarifier treatment process, the chemicals being used as coagulants to separate the water from unwanted sediments such as the alum and PACl should yield a total of 3.0 protozoa log credit. Coagulation and Sedimentation should yield 2.5 log credit while Filtration from the Sand Filters should yield 0.5 log credit. When a 3.0 log credit is obtained it means that the water is clear, no turbidity, and the water is 99.99% pathogen free. In the addition of chlorine gas, the MAV mentioned in the DWSNZ is 5mg/L. It is also worth noting that disinfection of the treated water should never be compromised. Fluoride, on the other hand, has a MAV of 1.5mg/L. Ultraviolet light disinfection should also meet a compliance criteria. The log credit assessment for this process is 3.0. To be able to obtain a protozoa log credit for UV disinfection, all water must pass through the UV reactors, and should meet compliance monitoring. In addition, the procedures and requirements are specified in the Ultraviolet Disinfection Guidance Manual (Ministry of Health, 2008).
The criteria for monitoring E. coli in the Waikanae facility is criterion 5. The pH of the drinking water is also mentioned in the Standards as an aesthetic determinand. The guideline value of the pH should range at 7.0-8.5 because water with a low pH have a high plumbosolvency. The suggested pH value should be 8.0 for effective disinfection of chlorine.
In summary, before the water leaves the treatment plant, the DWSNZ is strictly imposed before any drinking water is distributed to the public. Furthermore, all the above mentioned Priority 2 determinands must be monitored by the supplier.
Another aspect of the DWSNZ introduces a statutory requirement that all drinking-water supplier providing drinking water to over 500 people must develop and implement a water safety plan (previously known as a Public Health Risk Management Plan) to guide the safe management of their supply (section 69Z). Essentially, a water safety plan includes the identification of any public health risks, critical points, and mechanisms for preventing any potential risks that may arise in a drinking-water supply. (Online Lecture Notes, 2017).
Identifying the critical points in the treatment process and distribution system would provide good efficiency assurance. The critical points in the treatment process would include the proper monitoring of any potential hazards, and record keeping that includes details of the treatment plant, the barriers, and sampling or testing and its results. The critical points that may arise in the WWTP includes: the components of raw water, and damages to treatment plant equipment. Meanwhile, the critical points in a distribution system are those points where procedures for equipment failure lead to a public health hazard. There are two types of critical points involved in the distribution system: supply loss and water contamination.
The loss of supply may be contributed to the loss of water supply from the source, treatment failure, and water contamination. The risk to the community cause by this critical point does not only affect thirst but those used for fire-fighting, industries, sewage, and personal hygiene. On the other hand, water contamination which is an obvious risk to the public, can occur due to the intrusion of contaminants or by unforeseen chemical reactions within the system.
In relation to the Critical Points, all the above mentioned processes are being monitored in a systemised computer program which shows the schematics of the whole plant. It allows the team to immediately identify the problems whenever it arises. It also gives a detailed information on recorded water flowrates which is beneficial when analysing data especially in longitudinal researches where it requires long term recorded data. Each process has its own alarm whenever something goes wrong. For example if a chemical concentration is high or something is faulty, it will automatically shut the whole plant as a contingency response. See Appendix 22 for the Supervisory Control and Data Acquisition diagram used in the Waikanae Water Treatment Plant.
The purpose of having a legislation and a standard for drinking water is to ensure the safety, and protect the health of the people and community by promoting adequate supplies of safe drinking water from all supplies. As a result, the process of treating the drinking water should comply with the said Standards. From the catchment to the treatment process, all possibility of hazards must be minimised or should even be eliminated. Basing from the assessment and gathered information, the Waikanae Treatment Plant is an example of a water supplier which strictly abides with the DWSNZ. It manages to provide service for an estimated population of 40,000 people while also ensuring that the water being treated meets the regulated and mandatory compliance.
This research has also illustrated the Public Health Grading of the Waikanae Treatment Plant, where it assessed the contaminants which are present in the Waikanae River, The local authority (Kapiti Coast District Council) and the public health service (Hutt Valley District Health Board) involved in the operation of the plant. It also provides information regarding the total water being collected and produced by the facility, if it complies with the DWSNZ on coagulation and filtration treatments, the aesthetic determinands, the protozoa log credit compliance, and standards of controls. The process of distribution is also graded which looks at the pipes, leaks, or anything essentially worth of being inspected and monitored under the Drinking-water Standards for New Zealand 2008.
So whenever we use water, it is also our duty to ensure that our drinking water is conserved and we should use water responsibly. As presented in this report, the efforts, and meticulous procedure which the drinking water goes through in order to reach our homes, it is everyone’s responsibility to conserve water to reduce the events of water shortages due to excessive water use. It is then this report’s conclusion to reiterate the water conservation initiative to emphasise our responsibility as consumers as there is always a limit in the use of our available water supplies.
For the following images, some were taken from the provided photos online (MASSEY STREAM) and some were taken during the visit to the Water Treatment Plant.
Controls for the dosing of Chloride, Fluoride, and Lime
Fluoride, Chloride, and Lime dosing. On the left in the building is UV filter plant.
These SCADA images were taken from STREAM and dated 2010. I noticed during the trip that the WWTP now use an updated version for their SCADA.
Bassett, D. (n.d.). Dealing with Water Shortages: Bore Versus River. Retrieved from https://www.waternz.org.nz/Attachment?Action=Download&Attachment_id=1304
Greater Wellington Regional Council. (2014). Waikanae River Environmental Strategy. Wellington: Greater Wellington Regional Council.
Health (Drinking Water) Amendment Act. (2007). Retrieved from http://www.legislation.govt.nz/act/public/2007/0092/latest/DLM969835.html#DLM969845
Health Act. (1956). Retrieved from http://www.legislation.govt.nz/act/public/1956/0065/latest/DLM305840.html
Kāpiti Coast District Council. (2007). Waikanae Water Treatment Plant. Wellington: Kāpiti Coast District Council.
Kāpiti Coast District Council. (2015). Water Supplies and Treatment. Retrieved from http://www.kapiticoast.govt.nz/services/A—Z-Council-Services-and-Facilities/Water/Water-Treatment/
Ministry of Health. (2008). Drinking-water Standards for New Zealand 2005 (Revised 2008). Wellington: Ministry of Health.
Online Lecture Notes. (2017). 214.314 Online Lecture Notes. Wellington: Massey University, School of Public Health.
Study Guide. (2017). 214.314 Water and Waste Treatment. Wellington: Massey University, School of Public Health.
Water Information New Zealand. (2017). Drinking Water for New Zealand. Retrieved from http://www.drinkingwater.esr.cri.nz/general/waterdatabase.asp