Drinking water

role of the ministry of health for drinking water

maintains a register of all drinking-water standards suppliers issues drinking-water standards imposes duties on suppliers to monitor their supplies and take all practicable steps to comply with the standards imposes duties on water carriers recognised laboratories suitable to carry out analyses set out emergency powers disseminates information about drinking-water standards.

Adequate supply

(a) the minimum quantity of drinking water that is required by the occupants of that property, on an ongoing basis, for their ordinary domestic and food preparation use and sanitary needs; OR (b)if regulations have been made under section 69ZZY(1)(a) prescribing the quantity of drinking water, or a formula for determining the quantity of drinking water, that is an adequate supply to a property, the amount specified in, or calculated according to the formula set out in, those regulations

MoH role in Health act 1956 Part 2A

- Maintain register of DW suppliers - issue DW standards. - impose duties on suppliers to monitor and take all practicable steps comply with the standards. - imposes duties on water carriers. - recognises labs - sets out emergency powers - disseminates information about DWSNZ

6 fundamental principles in drinking water safety ( havelock north)

- a high standard of care must be embraced. - protection of source water is paramount - maintain multiple barriers to contamination - change precedes contamination - suppliers must own the safety of drinking water. - apply a preventative risk management approach

Wholesome

- being potable - not containing or exhibiting any determinand in an amount that exceeds the value stated in the guideline values for aesthetic determinands in the drinking-water standards

How sedimentation works

- decreasing the velocity of flow so that particles are less likely to remain in suspension and more likely to settle out under gravity. - requires efficient sludge removal and removal of clarified water with minimum disturbance. dependent on the up flow velocity equalling the settling velocity.

ideal disinfectant qualities

- destroy all pathogens introduced into the supply in reasonable time period, at different temperature ranges, concentrations and water conditions - non-toxic and no taint - cheap, safe, easy to store and transport, handle and apply. concentration of chemical easily determinable. - must persist in high enough concentration to provide a residual or the disappearance of residual should indicate recontamination.

requirements of a pipe used in distribution system

- must convey the quantity of water required. - must withstand all internal and external forces. - must be durable and have a long life. - must not leach toxic materials.

Factors affecting disinfection

- nature of organisms ( i.e. E.coli is more resistant than other organisms to chlorination; and distribution in the water ( less effective if organisms are clumped)) - nature of the disinfectant: stirring and good mixing is important. - Nature of water: presence of suspended matter and other organic matter. pH - temperature: higher the temperature of the water the quicker the disinfectant will work. - contact time: longer it is in contact with the organism, the more likely it will be to kill it.

major transgression

- one which immediately threatens the safety of the consumers.

transgression

- result of a test or monitoring of a determinant exceeds the MAV - specified operational performance parameter for a treatment process exceeds the operational limits for that parameter for more than the allowed extent or duration. -single sample or event

Key aspects of Health act part 2A

- suppliers must take all practicable steps to ensure they supply and adequate supply of drinking water that complies with the DWSNZ - Introduction and implementation of public health risk management plans - suppliers must take reasonable steps to contribute to the protection of source waters from contamination. - DG of Health appoints officers to act as assessors and determine compliance with the act and have competence internationally accredited. -record keeping and publication of information about compliance. - appropriate management of drinking water emergencies - improves enforcement by providing an escalating series of penalties for non-compliance.

consequences of not using cyanurates in outdoor swimming pools

- too low chlorine - economic costs of replacing large amounts of chlorine lost by photolytic decomposition

FAC residual required under DWSNZ

.2 mg/L at pH 8 ( because higher than 8 HOCl decreases rapidly)

complete equation for electrolytic generation of chlorine gas

2NaCl +2H2O=Cl2 (g) + H2(g) + 2Na+ +2OH- where Na+ is a spectator ion and excess is removed as NaOH

chloramine disinfection power compared to FAC

3mg/L-1 compared to 0.2 mg/L-1 collectively called combined chlorine

protozoal MAV

</=1 NTU

bacterial MAV

<1/ 100mL E.coli

effect of aeration on ammonia and organic nitrogen

At the end of the aerobic zone almost all influent ammonia nitrogen and organic nitrogen has been converted to nitrate. The return of this nitrate to secondary anoxic zone exposes the flow to anoxic conditions and biodegradable substrate required for effective denitrification.

Combined available chlorine

Chloramines

Oxidising chemical disinfectants

Cl, Br, I. Chlorine gas most commonly used and most economical.

impacts of chlorinated with chlorine gas

Gaseous chlorine continuously adds hypochlorous acid (HOCI) and hydrochloric acid to the pool water. This will cause a drastic drop in pH if not compensated for by continuous alkalinity and pH control. This is usually achieved by addition of soda ash or caustic soda upstream of the chlorine dosing point. this reflects the inherent dangers of mixing chlorine gas or solid with acid or alkali as chlorine is a reactive substance and can lead to explosion or the production of toxic fumes.

designated officer powers

Health protection officer or medical officer of health If the officer reasonably believes there is a serious risk to public health arising from a drinking water supply or lack of it s/he may: take immediate action or require immediate action to prevent reduce or eliminate any risk to public health arising from a supply require supplier to stop supplying drinking-water that has not been treated to make potable require all persons within a specific area to use an alternative supply. publish statements related to the serious risk or harm to health (which could include the boiling of water).

integrated waste management

Integrated waste management is base on a hierarchical principle of waste minimization, reuse, recycling, composting and resource recovery prior to disposal of waste residues to minimise the environmental impact of commercial and industrial waste streams

compliance order

Medical officer of health issues requiring that person to stop, or prohibiting that person from starting, anything done or to be done by, or on behalf of, that person that the medical officer of health believes, on reasonable grounds, contravenes, or is likely to contravene, this Part; or will or may create a risk to public health arising from that person's drinking-water supply; or requiring that person to do something , on reasonable grounds, is necessary to— ensure compliance by, or on behalf of, that person with this Part; or prevent, remedy, or mitigate any risk to public health arising from that person's drinking-water supply. A compliance order may be made subject to conditions. A compliance order may specify the time within which compliance must be achieved.

Chemical formula for chloramines

NH2Cl NHCl2 NCl3 And water as a bi product.

electrochemical generation of sodium hypochlorite

NaCl + H2O+ 2e-= H2 (g)+ NaOCl chlorine gas is retained in solution so that it will instantly react with the sodium and chloride ions form NaOCl, hydrogen gas is vented to the atmosphere

nitrification

Oxidation of ammoniacal compounds to nitrites and then nitrates NH4 + O--> NO2 +O--> NO3 +H2O

sources of wastewater for Paraparaumu

Paraparaumu and Waikanae wastewater. septage delivered to the site from roadside tankers. Leachate from the Otaihanka Landfill

Oxidising agents

Potassium permanganate. Hydrogen peroxide. oxidising potential not necessarily related to disinfectant potential. Hydrogen peroxide is good oxidising agent but poor disinfectant.

water softening

Precipitation base exchange softening

brownian motion

Random motion of particles due to their erratic collisions with fast moving molecules in the fluid

Reason for maintaining pool pH at 7.2-8

Reactions leading to the breakdown of organic matter occur at pH 7.5. At pH >8 reaction moves to the right and OCl- Below 7.2 chloramine production is rapid ( smells, irritation). Less corrosion of metal fittings.

Why is breakpoint chlorination limited in practice?

Recirculating and consecutive dilution

advantages of chlorination

Taste and odour control prevention of algal growths filter media clean removal of iron and manganese colour removal by bleach controlling slime growth in reticulation restoring and preserving pipeline capacity mains sterilisation provides a ready means of checking if water is safe.

recognised laboratory

The Ministry of Health requires all sample testing to be performed by laboratories that have appropriate skills and quality assurance procedures and to be registered. Section 69ZY required the Director General of Health to maintain a register of Recognised Laboratories must meet general Requirements for the Competence of Testing and Calibration Laboratories and specific technical criteria i.e. fully IANZ accredited laboratories included in the register of recognised laboratories. the ministry of health has the authority to recognise laboratories

NES requirements for councils

The NES requires regional councils to ensure that effects of activities on drinking water sources are considered in decisions on resource consents and regional plans. Specifically regional councils are required to: decline discharge or water permits that are likely to result in community drinking water becoming unsafe for human consumption following existing treatment be satisfied that permitted activities in regional plans will not result in community drinking water supplies being unsafe for human consumption following existing treatment place conditions on relevant resource consents that require notification of drinking water suppliers if significant unintended events occur (eg, spills) that may adversely affect sources of human drinking water.

NES- purpose

The National Environmental Standard for Sources of Human Drinking Water. sets requirements for protecting sources of human drinking water from becoming contaminated. a human drinking water source is a natural water body such as a lake, river or groundwater that is used to supply a community with drinking water. The standard applies to source water before it is treated and only sources used to supply human drinking water ie, not stock or other animals. Contaminants such as microorganisms can pose a risk to human health when they enter drinking water supplies and that water is then consumed. Taking steps to prevent such contaminants from entering drinking water sources is part of a multiple barrier approach to reduce this risk to people.

how is aeration controlled in aerobic zone

There are DO probes in each pf the zones which control the level of aeration by adjusting airflow control valves and the speed of blowers.

Pool hardness

Total concentration of calcium and magnesium. Expressed as mg/L calcium carbonate equivalence in the same manner as alkalinity. High hardness combined with high alkalinity gives rise to scale which can block pipes and increase cloudiness

Parameters governing the formation of disinfection biproducts

Type and amount of organic material, pH, temperature.

Disinfecting by light

UV - can be done artificially by a mercury vapour lamp made of quartz. water has to be free of light absorbing particles such as phenolic and other aromatic compounds and free from suspended matter that would shade organisms against light. NO RESIDUAL

primary anoxic zone

a zone which is low in oxygen with nitrate/nitrite present the aim is to remove nitrogen. Bacteria are presented with a food source in the absence of dissolved oxygen. This forces them to use chemically bound oxygen which comes from nitrates/nitrites. this process causes nitrogen to be emitted as a gas. NO3 --> O + N2 (g).

suitability of cyanurate for outdoor swimming pools

acts to stabilise the chlorine chemical so that it may persist for days rather than it being dissipated by the UV light within hours of dosing. cyanurate reacts to produce chlorinated isocyanurates. these compounds are stable in sunlight and act as a reservoir for more chlorine to be released as it is decomposed by sunlight. cyanurates exhibit a limited degree of hydrolysis in water so that a constant supply of active chlorine. HOWEVER excessive levels of cyanurate will adversely effect the equilibrium of free chlorine.

Super chlorination

addition of a large quantity of chlorine to achieve disinfection. removes tastes, odour, iron and manganese is achieved by superchlorination.

pre and post chlorination

addition of chlorine before and after treatment

re chlorination

addition of chlorine to finished water at one or more points in the reticulation system to ensure adequate disinfection

Principles inherent to 'taking all practicable steps'

all steps that are reasonably practicable in the circumstances having particular regard to the availability, affordability, nature and severity of harm, current state of knowledge about the arm, and the means to achieve such a result.

Chlorine demand

amount of chlorine that is reduced or converted to inert or less effective forms by substances in the water. chlorine is a non- selective oxidant and thus will react with many substances that may be present in water and their reduced products. Chlorine demand varies with chlorine contact time, pH , temperature and this is a condition that much be reached before adequate disinfection can occur.

Anaerobic

any form of oxygens excluded. raw wastewater mixed with effluent from anoxic zone creates famine conditions causing some organisms to release phosphorus and orthophosphate into liquid. energy released in this reaction is used to store short chain fatty acids for future use in anoxic and anaerobic zones. bacteria present also convert suspended solids and dissolve slowly degrading organic matter into readily available BOD.

Simple chlorination

application of chlorine to untreated water with no other treatment provided

Combined residual chlorine

application of chlorine to water and a subsequent section with ammonia to produce chloramines.

FACE

as pH exceeds 8, HOCl concentration rapidly reduces. thus as pH value changes, chlorine values have to be adjusted to meet the same equivalent power. essentially FAC must be increased as the pH increases to achieve the same disinfection power.

wholesome water

being potable; and (b) not containing or exhibiting any determinand in an amount that exceeds the value stated in the guideline values for aesthetic determinands in the drinking-water standards as being the maximum extent to which drinking water may contain or exhibit the determinand without being likely to have an adverse aesthetic effect on the drinking water

common themes between flint and havelock north

callous disregard for public health integrity of source waters wait and see approach failure of consultants failure of regulatory agencies

temporary hardness

carbonate hardness because it can be forced to precipitate by prolonged boiling.

water hardness

caused by the presence of divalent metallic cations. e.g. Ca2+, Mg2+, Fe2+ and Mn2+. usually represented as the estimation of calcium and magnesium and expressed as g/m3 of equivalent calcium carbonate

chemical coagulation process

chemical feed mix for even distribution coagulation flocculation

consequences of too much cyanurate

chlorine lock: where FAC is lowered

chemical storage conditions

clean dry well ventilated cool secure away from sunlight not cyanurates and calcium hypochlorite together as explosive

colloids of interest in water treatment

colloidal clay large organic molecules oxides of iron, manganese and silicon precipitated aluminium hydroxide and other coagulants.

shoebox septic tank

consists of a tank which contains an inlet to receive household waste solids settle out at the base where they are digested under anaerobic conditions. effluent digests under aerobic conditions with air provided by a vent. effluent is then disposed of by irrigation in a trench, now regarded as outdated and have serious potential for tank and trench failure. some communities they are a serious health hazard and nuisance. attempts to carry out both sedimentation and digestion in one compartment. digestion at the bottom often produces gases which bring sediments to the top and interfere with the sedimentation process. causes a heavy scum to form on the surface. this overflows into irrigation trenches causing creeping failure.

Breakpoint chlorination

continuous chlorination of water to the point where demand has been satisfied and all the ammonia has been oxidised leaving free available chlorine.

Carbonaceous oxidation

conversion of organic compounds to water and carbon dioxide CxHxOx +O--> H2O +CO2

safety issues to do with electrolytic generation of chlorine

corrosive environment process requires competent operation to maintain he correct operating conditions such as salinity, alkalinity, pH, water hardness. must be generated straight into the pool water as maintaining in cylinders is a safety concern.

combined residual chlorine

defined as the amount of chlorine which has reacted to produce less effective forms.

chloramine distribution

dependent on the concentration of the reactants and the pH.

health effects of trihalomethane's

dermally absorbed and inhaled inhalation anaesthetic hepatotoxic nephrotoxic may cause dermal reddening, burning, blistering Chronic oral exposure of humans to chloroform at high doses results in adverse effects on the central nervous system, liver, kidneys and heart. carcinogenic

disinfecting by heat

destroys all important waterborne diseases. same time temperature relationships as milk.

sanitary significance of chlorine

disinfection power is proportional to the concentration x contact time.

Ozone disinfectant

good but relatively expensive. normally leaves no residual has advantage of destroying odours and effectively bleaching colour

filtration process

gravity sedimentation ( immediately above sand grains) Interception ( strained by grains of sand) Adsorption (Chemical build up on sand particles; positive charge removing negative or colloidal particles passing through).

requirements of water safety plan

identify public health risks associated with supply - identify critical points in that drinking water supply - identify mechanisms for preventing public health risks arising in the drinking water supply and include information about costs and benefits -reducing and eliminating risks if they do arise, including a timetable for managing the public health risks that have been identified as being associated with that drinking water supply.

Health act section 69Z

imposes a duty to prepare and implement a Water Safety Plan to: - identify public health risks associated with the supply -identify critical control points in the supply - identify mechanisms for : preventing public health risks from arising, reducing and eliminating those risks if they do arise, including information about the estimated costs and benefits, set out a timetable for managing the public health risks that have been identified, comply with any additional requirements imposed by the director general of health

Phosphorus uptake

in aerobic zones, micro-organisms that stored short chain fatty acids utilise these acids as food for growth and to replenish their stores of phosphorus. they compensate for famine conditions in anaerobic zones by taking up excess phosphorus. the microbes retain phosphorus and it is removed from the liquid stream when bacteria are wasted in the WAS

potable water

in relation to drinking water, means water that does not contain or exhibit any determinands to any extent that exceeds the maximum acceptable values (other than aesthetic guideline values) specified in the drinking-water standards

odour control

inlet structure and the septage recieval sump are covered and the headspace atmosphere is extracted by the odour control blower. the odorous air is diffused into aeration zone 6 for biological treatment

Contamination

introduction of a substance or organism to a water source or water that does or doesn't usually require treatment to make it consumable that either: - makes it unpalatable or unsuitable for human consumption; or requires that water to be treated to make it palatable or suitable for human consumption without intensified, or enhanced, or alternative, drinking-water treatment to make it palatable or suitable for human consumption

Water softening: Base exchange

ion exchange resin using styrene based polymers as a framework for holding sodium ions Ca2+ + Na2R--> 2Na+ +CaR Mg2+ +Na2R--> 2Mg+ + MgR resin is in the form of spherical beads and the water is rendered completely soft by allowing it to pass through. eventually all sodium ions on the resin will be replaced with calcium or magnesium ions and the resin will be said to have been exhausted, however the reaction can be reversed and thus the bed regenerated.

drinking-water assessor

means a drinking-water assessor appointed under section 69ZK; and includes, in the case of a drinking-water assessor that is an agency, an employee or a contractor of that agency engaged in carrying out the functions of a drinking-water assessor The Director-General must be satisfied that the person or agency— (a) has the experience, technical competence, and other qualifications to undertake the functions of a drinking-water assessor; and b) is accredited to internationally accepted standards for inspection bodies to perform the functions specified in section 69ZL; and (c) has in place effective arrangements to avoid or manage any conflicts of interest that may arise.

Critical points

means the points in a drinking-water supply at which it is possible for the supplier to eliminate, minimise, or isolate hazards to the drinking water that may result in failure to comply with this Part or with the drinking-water standards

director general of health requirements

must maintain a register of: networked supplies bulk supplies water carriers and operators of designated ports self-suppliers who supply water to community -purpose buildings owned by them.

Permanent hardness

non-carbonate hardness as it cannot be removed by prolonged boiling.

Backwashing

occurs when head loss is greater than 2m or on a time interval. water is forced up in the reverse direction lifting off dirt on the top layer of the filter medium and sending it to waste. some plants have an air scourer which breaks up caked dirt prior to washing.

balancing pool water

pH alkalinity hardness

electrochemical generation of chlorine

pass an electric current through salt brine in an electrolytic cell using special electrodes. at the anode (+) electrodes are lost from chloride Cl- to form molecular chlorine gas Cl2(g). 2Cl-= Cl2 (g)+2e- at the cathode (-) H+ electrons are gained to form hydrogen gas H2 (g) 2H+ +2e-=H2 (g)

critical control points definition

points, steps or procedures in which controls can be applied to water treatment so hazards can be prevented, eliminated, isolated or minimised t acceptable levels.

causes of flocculation failure

poor quality chemicals. chemical supply exhausted. coagulant dose pump failure. dosing malfunction leaks and loss from chemical storage tanks faulty dose rate pH not correct for process inadequate mixing of coagulant. insufficient time for floc formation and settling obstruction to flow rates in sedimentation.

objective of chlorination

prevention of algal growth destruction of organic maintenance of water aesthetic quality.

Plumbosolvency

priority 2c- chemical determinants which may appear in drinking water having arisen from a consumers plumbing or fittings. ( Ability of water to dissolve pipes/ aggressiveness). increases when water lies dormant in contact with metal fittings.

definition of coagulation

process in which stable colloidal suspensions are destabilised and particles start to mass together.

Secondary Anoxic

purpose: denitrification. flow from anaerobic zones mixed with A-Recycle flow. A-Recycle flow is relatively high and recycles a nitrate rich liquor, from the aerobic zones, which is denitrified when it is mixed with the food from the anaerobic zones in the absence of dissolved oxygen

rationale for residual

raw water is often of poor quality. oxidation of iron and manganese occurs objectionable odours and tastes are present contact times are insufficient to achieve disinfection by combined chlorine forms resistance bacteria and after growths are present.

What is the risk associated with intermittent dosing

reverting back passed break point chlorination. thus intermittent dose must be very high. also needs to be varied to anticipate higher bather loads.

conventional treatment train

source water --> straining--> coagulation--> clarification--> filtration --> disinfection --> Fluoridation.

other benefits of using cyanic acid

stabilisation of chlorine compound under photolytic conditions. more uniform chlorine residual control improved disinfection. reduced chlorine consumption.

critical control point examples

staff competence, knowledge, training and skill. - general monitoring and lab evaluation. - chemical dosing. - source water. - clarification/ sedimentation - sand filtration/ filters - alternative disinfection such as ozone or UV - chlorination and pH correction - distribution pumps - reservoir - distribution.

water softening: precipitation

takes advantage of low solubilities of calcium and magnesium. use lime or soda ash Ca(HCO3)2+ Ca(OH)2 -->2CaCO3(s) +2H20 calcium bicarbonate + Lime --> insoluble carbonate. however other calcium and magensium salts remain after this process. perfected when soda ash is added CaSO4 +Na2CO3--> Na2SO4 +CaCO3 this will achieve hardness down to 25g/m3 due to natural solubilities of Mg(OH)2 and CaCO3

Chlorine demand

the amount of chlorine reduced or converted into less active forms by substances in water ( organic matter). Demand varies with pH, temperature, contact time. Expresses a definite equilibrium of the chemical reactions of chlorine in wate under known conditions

Pollution

the introduction of a substance or organism into drinking water or a drinking-water supply system that causes or may cause that water, or as the case requires, water in that system, to exceed the maximum acceptable values for determinands specified in the drinking-water standards

function of drinking water assessor

to assess the performance of drinking-water suppliers to determine whether or not they are— (i) complying with the requirements of this Part; and (ii) complying with the requirements of the drinking-water standards; and (iii) implementing their water safety plans; and to notify non-compliance to provide the DG with records and information in relation to compliance with requirements. to assess the competence of persons to analyse samples of raw water or drinking water, to calibrate equipment used to treat or monitor raw water or drinking water, or to undertake any other task required to ensure compliance with this Part, the drinking-water standards, or a water safety plan; and to verify the adequacy of, and, where appropriate, approve water safety plans prepared by drinking-water suppliers or other persons and to certify the implementation of those plans; and check that complaints received by drinking-water suppliers are recorded and responded to appropriately; and they are accountable to the director general for their functions.

purpose of grit removal

to reduce erosion and damage to downstream equipment. uses a vortex flow pattern chamber a removal pump and a grit clarifier.

pool hardness

total concentration og calcium and magnesium expressed as mg/L (or ppm) calcium carbonate equivalence in the same manner as alkalinity. High hardness, when combined with high alkalinity, will give rise to scale, which will block pipes and filters and may turn the pool water cloudy. As heat promotes scale formation, heat exchange units are particularly prone to scale blockage. and poor visibility. can be reduced by adding fresh water or dosing with caustic soda

method of aeration

uses a fine bubble diffuse aeration system to emit small air bubbles from the bottom of the tank to slowly aerate. This provides substantial and efficient mass transfer of oxygen to the water.

aerobic zone

uses a fine bubble diffused aeration system to supply air. this is necessary for the oxidation of carbonaceous material the conversion of ammonia to nitrates to provide the conditions for the luxuriant uptake of phosphorus to keep the contents of the zones in suspension. there are six zones in the series. scum is manually removed by a weir penstock, flows by gravity to scum pump station.

chemistry of cyanic acid in water

weak trivalent acid, low solubility in water. hydrolyses in water and dissociates to yield H+ or Cl+. then forms ionic bonds between Cy and Cl which thus provide the stabilisation of Cl in the presence of sunlight.

planning aspects

wet weather flows to plant are stored in activated sludge plant. in severe/ prolonged wet weather offline storage is provided in an open storage basin. may overflow directly to mazengarb drain monitored and controlled though online monitors. uses SCADA system for alarms, changing set points, and assessing current and historical data. septage import tank has headspace and is monitored with alarms for explosive conditions have significant flow balancing methods to ensure the process is not overloaded.