DE6206 & MG6110 Water and Waste Management
How is design regulated for AS/NZ 1547:2012 (on site treatment)
*5.4.1 Performance requirements for wastewater treatment units* a)Be of sufficient capacity to receive and treat all wastewater outputs from premises on the property b)Produce effluent suitable for land application system c)Avoid the likelihood of creating unpleasant odours, or the accumulation of offensive matter; and d)Use of minimal energy resources.
What are some of the advantages and disadvantages of recirculation sand-filters?
*Advantages* •Closed units minimse potential for offensive odours, infiltration, and freezing •Small footprint •Easy installation •Minimalmaintenancewithout site disturbance •Typically over 95% removal of biochemical oxygen demand (BOD) and total suspended solids (TSS) *Disadvantages* •Suitable for low and intermittant flow situations only •More suited to low gradient land as opposed to flat land(for land disposal) •More suited to permeable soils than impermeable soils(for land disposal)
What are some of the advantages and disadvantages of evapo-transportation beds?
*Advantages* •Low cost •Easy to construct •Easy to use •Easy to repair *Disadvantages* •Can clog or overflow •May be a risk during to small children (due to potential for drowning) •Can smell slightly •May attract insects •Evaporation process requires time •Only applicable to hot and dry climates •Are not suitable where ground is rapid draining
What are the three classes of micro-organisms that might cause disease in drinking water?
*Bacteria* • Indicator organism Escherichia coli (E. coli) is used to assess this. • E. coli itself is generally non-disease causing • If E. coli is <1 organism in 100ml then bacterial quality of water is acceptable. *Viral* • No viral indicator at present • E. coli may also signal viral contamination *Protozoa* (e.g. Giardia and Cryptosporidium) • Common cause of infection and disease • MAV 1 organism per 100l (note - NOT millilitres)
What is biological aeration?
*Biological aeration is either used in combination with a biological trickling filter or in small plants as the biological treatment process.* Wastewater containing organic matter (BOD) enters the tank. Bacteria metabolise the waste organics when dissolved oxygen is present and in turn they release carbon dioxide. Protozoa feed on the bacteria. Aerating wastewater removes organic matter from solution by synthesis into microbial cells (biological floc). This mixed liquor (ML) is transferred to a clarifier for settling. Mixed liquor and the biological growths are called mixed liquor suspended solids. When this is recirculated into aeration tanks this is referred to as activated sludge as the micro-organisms are very active at removing soluble organic matter.
What is the difference between black water and grey water?
*Blackwater* is wastewater containing fecalmatter and urine (iecontaining toilet waste) Wastewater from sources other than toilets, e.g. showers, hand basins, laundries, dishwashers, kitchen sinks is called *greywater*. Greywater can be used (often without treatment) for toilet flushing and irrigation.
What are the two most common disinfection methods for wastewater effluent?
*Chlorination* •Chlorine dosage depends on wastewater strength, pH, presence of substances which inhibit chlorination, temperature and contact time. •Chlorination by-products (trihalomethanes) can be a health hazard. *Ultra violet* •Inhibits organisms reproducing by damaging their DNA.
What are the compliance criteria and remedial requirements of the DWSNZ?
*DWSNZ have set compliance criteria for meeting drinking water standards. Outlined in Sections 4-12 of the DWSNZ.* The compliance criteria include: • How to test • Where to test • When / how often to test / monitoring period • The number of allowable MAV exceedances The level of testing required / compliance criteria for each water supply will depend on the raw water quality, treatment process and (often) population served. DWSNZ also sets out remedial measures where there is a transgression (non-compliance).
What determines the degree of disinfection effectiveness under the DWSNZ?
*Degree of disinfection effectiveness depends on:* • Residual disinfection concentration • Contact time • pH • Turbidity • Flow rate through treatment plant (for ozone and UV treatment)
How is sludge thickened achieved mechanically?
*Dissolved air flotation* •Fine air is released and attaches to sludge, causing it to float. •Typically achieve 4% solids concentration for activated sludge and 85% solids recovery. *Gravity belt thickeners* •Moving permeable fabric belt •Water drains and solid is retained on the belt. •Polymer (to liberate water and bind solids) is added in a flocculation tank prior to entering the belt. •Increase solids concentrations from 0.5-1% to 4-6%. *Centrifuge thickening* •Solids and liquids separated by rapid rotation •Increase solids concentrations from 0.5-2% to 4-8%. •Obtain high solids concentration. •More expensive than other options.
What are some things that can affect effluent quality with biological treatment?
*Effluent quality* Affected by influent quality. Generally single stage filter removes 85% of BOD. Therefore to achieve 30mg/l effluent, influent must be <200mg/l. Affectedby temperature BOD removal reduced in winter. Can use covers in winter. Odours Possible in anaerobic zone of filter air must be circulated Pests Filter flies (Psychoda) and filter snails are a nuisance in warm weather mostly to plant personnel and (for snails) causing wear and tear on machine
What are the characteristics of chemical contamination of drinking water under the DWSNZ?
*Generally we are concerned with low dose, long exposure contaminants* There are three contaminants where acute exposure is of most concern: • Nitrate (specifically for bottle-fed infants - concentrations over 100mg/L should not be consumed) • Cynatoxins (toxins produced by cyanobacteria or blue-green algae) • Copper (from corroding pipes, if in sufficient concentrations) *However, any chemical contaminant in high enough concentration could be of concern*
What is extended aeration?
*Good for treating small wastewater flows (i.e. low BOD loading) •Continuous wastewater mixing by diffused air or mechanical aerators in tanks. •Very stable process •Aeration periods of 24-36 hours. •Solids settled in clarifier (with long detention time and low overflow rates) and returned to aeration basin. •Sludge is generally removed every few weeks from the aeration tank when the aeration is turned off. •Larger extended aeration facilities include aeration tank, clarifier and aerobic sludge digester.
How can sludge be disposed of?
*Incineration* •Turns dewatered sludge into inert ash. •The process is self-sustaining if incoming sludge is dewatered to 35% solids. •Process works better with higher calorific value, undigested sludge. *Agricultural land application* Biosolids can be used as a soil conditioner and fertiliser. •Liquid disposal of digested biosolids is popular if possible (will likely depend on haulage distance). Dewatered sludge will reduce sludge volume and therefore haulage costs. •A RMA resource consent would be required for discharge of solids or effluent to land. Restrictions are likely to be placed on contaminant levels such as pathogens (fecal coliforms), heavy metals, selected organic compounds and nutrient levels. Level of restrictions will depend on the use of the site. Restrictions on land disposal are likely for wet weather or on snow- covered or frozen ground. •Environmental concerns include: pollution of ground and surface water, contamination of soil and crops and transmission of diseases.
What are the National Environmental Standards for Sources of Human Drinking Water Regulations 2007
*Initiated so that authorities had to consider drinking water sources when permitting things under the RMA.* -NES applies to registered water sources before they are abstracted - after that it is governed by the Health Act *The NES has three main components that apply to:* 1. resource consents (regulation 7 and 8) 2. permitted activity thresholds in regional plans (regulation 9 and 10) 3. emergency notification conditions that may be placed on resource consents (regulation 11 and 12)
What are the purposes of the inlet zone, outlet zone, settling zone and sludge zone in the treatment process?
*Inlet zone* - in this zone, the incoming water has to be slowed and spread evenly across the basin to ensure that short circuiting does not occur and that flocs (from coagulation and flocculation process) do not break up. *Outlet zone* - designed to prevent short-circuiting and prevent sediment leaving the basin. Usually at top of basin. Often a v-notch weir configuration is used. *Settling zone* - where sediment settles out of the water. *Sludge zone* - this zone is where the sediment collects. It is removed either manually or automatically by scraper arms. It is important to keep velocities low so as not to remobilised the sediment. This area needs to stay aerobic. If it turns anaerobic (no or low oxygen) then it may become septic which causes taste and odour problems.
How can chemicals from industrial processes be removed?
*Iron and magnesium are frequently found in raw waters or when water has been in contact with iron pipes.* Can be removed by oxidising process for clear waters or the use of lime, or iron coagulants followed by rapid sand filtration for turbid water.
What are the key constituents of waste water?
*Physical* Suspended solids *Organic chemical constituents* Biochemical oxygen demand Chemical oxygen demand Refractory organics (organics that resist traditional waste water treatment methods) *Inorganic chemical constituents* Nutrients Priority Pollutants (e.g. carcinogenic compounds) *Heavy metals* Dissolved inorganics (e.g. calcium, sodium etc) *Biological* Pathogens
How can water systems be contaminated in the distribution system?
*Pipes, water storage facilities (tanks or reservoirs) and any other components between the treatment plant and the consumers' property boundary.* *Contaminants enter the system through,* • *Leaks* (unlikely to have ingress due to pressure) • *Tanks* - vandalism, animals, • *Pipes* - corrosion
How do intermittent sand-filters work?
*Process* •Treats effluent from septic tank. •Effluent is distributed (using perforated pipes) over the surface of a bed of sand (>600mm deep) (underlain by gravel>150mm deep) •Treated water is collected by an underdrainage system. Pipes spaced at approximately 3m. •Biological slime and microorganisms grow in the voids of the sand near the surface helping to process the effluent but needing to be removed periodically. *Operation* •Effluent is applied two to six times per day. •Eventually the surface layer of sand to become clogged and need to be replaced . •When treating normal sewage, the application rate should not exceed 120lper 1m² per day •An effective I.S.F can remove 95% or more of the BOD and suspended solids in the raw sewage.
What is Pre-Treatment?
*Provides a buffer against changes in water supply quality.* • Can be used to modify water chemistry and/or contaminants to aid treatment. • Can control biological growth.
What is the purpose of a sedimentation tank?
*Raw water treatment prior to biological treatment* Water slowly passes through the tank, grit collects at the bottom and is periodically removed Tanks can be rectangular or circular
What are some of the siting considerations for wastewater that is applied to land?
*Siting* •Avoid exposure to prevailing winds •Do not interfere with building or property set-back requirements •Above ground irrigation must comply with regulatory authority requirements •Below-ground irrigation must be visible above ground •Must be clear of groundwater, cope with flooding and avoid pollution of watercourses
What is sludge?
*Sludge is essentially the concentrated organic matter removed from the wastewater. •Sludge collected from treatment is approximately 5m³/1000m³ wastewater •Sludge handling, treatment and disposal represents about 1/3 of the capital costs and a higher percentage for operating costs. •Primary sludges are anaerobic and are being actively digested by bacteria. They must be dealt with before obnoxious odours occur. They can be readily dewatered. •Secondary sludges (following aeration processes) are flocculated microbial growths with entrained non- biodegradable solids and is largely odour free. •Solids concentrations in sludge is typically 4-6%.
What are the four mechanisms of filtration?
*Straining* - larger particles cannot pass through wholes in filter medium *Adsorption* - particles adhere to outside of filter medium *Biological action* - breakdown of particles by biological action (relevant to slow sand filters but generally other filters are too fast for a lot of this to occur) *Absorption* - substances soak into the filter medium (after media initially get wet, little absorption happens)
What is ozonisation?
*Stronger oxidising agent and disinfectant than Chlorine for viruses, cysts and oocysts* Can remove Cryptosporidium. High cost to set up. No residual disinfection capacity.
What are the two main types of stabilisation ponds?
*Tertiary* •After activated sludge or trickling- filter secondary treatment. •Reduces suspended solids, BOD, faecal micro-organisms and ammonia •0.3-0.6m deep for aerobic mixing and sunlight •Sunlight provides UV disinfection •BOD loads are less than 1.7g/m².d •Detention times are 10-15 days *Aerated lagoons* •Usually followed by facultative ponds. •3m-4m deep •Aerators mix suspended microbial floc and provide dissolved oxygen. There is no settling •BOD removal depends on aeration time, BOD loading and temperature •Odours may occur if the aeration is not working properly
What is the main change for the Health (Drinking Water) Amendment Act 2007?
*The amendment is a move from traditional reactive management to proactive risk approaches*
What are the WHO health based targets for drinking water?
*The guidelines use health-based targets, divided into:* • Health outcome target (allowable disease burden) • Water quality target (concentrations of determinands) • Performance targets (treatment efficiencies) • Specified technology (treatment technologies)
What are the main factors that effect filter efficiency?
*The main factors that effect filter efficiency are* - The quality of the incoming water (Turbidity, size and shape of sediments, chemical characteristics) Effectiveness of the previous treatment processes. How clean the filter is What type of filter it is
How are the New Zealand Drinking Water standards set?
*The standards are based on Maximum Acceptable Values or MAVs for three main types of contaminants:* • Microbiological • Chemical • Radiological MAVs for micro-organisms are the concentrations in drinking-water above which there is significant risk of contracting a waterborne disease. • For carcinogenic chemicals, the MAVs set in the DWSNZ generally represent a risk of one additional incidence of cancer per 100,000 people ingesting the water at the concentration of the MAV for 70 years. • For most chemicals MAVs are calculated as the tolerable daily intake (TDI) which is the dose below which no significant risk to a consumer drinking 2L per day for a lifetime
How is protozoa compliance achieved under the DWSNZS?
*To design the process you need to know* • The concentration of Cryptosporidium in source water • Efficiency of treatment process in removing this. Chlorine is relatively ineffective against Cryptosporidium. Chlorine dioxide, ozone and UV radiation are more effective. Generally removed through filtration and coagulation and flocculation (covered in weeks 3 and 4) • Treatment process are awarded log credits depending on the effectiveness of the treatment process. You need different numbers of log credits depending on source water concentration of Cryptosporidium. Log credit scales are logarithmic.
What is the purpose of the drinking water quality standards for New Zealand?
*To protect human health* by • Setting water quality standards (MAVs) • Establishing compliance criteria and reporting requirements • Outlining remedial actions *These standards are a legal requirement for drinking water suppliers*
Why is it important to know what waste is being produced?
*Waste reduction*:Howmuch can be recycled *Waste treatment*:Energy potential of waste *Landfill operations*: Weight / volume of waste; gas generation calculations *Waste management planning*: Collection and disposal system planning and costings
What are the Emergency Provisions for the National Environmental Standards for sources of drinking water 2007?
Emergency provisions: • Consent holders must notify authorities if any event occurs which may compromise quality of a drinking water supply serving >25 people for more than 60 days a year. • Implemented using resource consent conditions.
What is pre-oxidation in the pre-treatment process?
Addition of chlorine, ozone or potassium permanganate can aid removal of natural organic matter (NOM) in the later coagulation/flocculation treatment. Can also be used to remove metals such as iron, manganese and arsenic.
What is the purpose of the waste minimisation act?
3. Thepurpose of this Act is to encourage waste minimisation and a decrease in waste disposal in order to— (a) protect the environmentfrom harm; and (b)provide environmental, social, economic, and cultural benefits.
What is the Health (Drinking Water) Amendment Act 2007 69A(1) (catchment)
69A(1) *The purpose of this Part is to protect the health and safety of people and communities by promoting adequate supplies of safe and wholesome drinking water from all drinking-water supplies.* "(2) Accordingly, this Part— "(a) provides for the Ministry to maintain a register of all drinking-water suppliers; and "(b) provides for the Minister to issue or adopt drinking-water standards; and "(c) imposes a range of duties on drinking-water suppliers, including duties to— "(i) monitor drinking water; and "(ii) take all practicable steps to comply with the drinking-water standards; and "(iii) implement risk management plans; and "(d) imposes a range of duties on water carriers; and "(e) provides for the appointment of drinking-water assessors to assess compliance with this Part, and sets out their functions and powers; and "(f) provides for the Director-General to recognise laboratories for the purposes of analysing drinking water; and "(g) sets out certain emergency powers that are available during public health emergencies relating to drinking water; and "(h) creates various offences; and "(i) provides for the dissemination of information about drinking water.
How is E.coli tested for?
APHA 9223 B - Enzyme Substrate Coliform Test. Uses cultivation of water on a specific substrate (media) to detect the presence of E Coli. A colour change indicates the presence of E Coli.
Why is oxygen added in the pre-treatment process (aeration)?
Adding oxygen can aid: • oxidisation of iron and manganese • removal of gases (hydrogen sulphide, carbon dioxide, methane) • removal of volatile contaminants (vinyl chloride, trichloroethene) • Removal of tastes and odours • Can be achieved through sprays, trickling towers of bubbling air through water.
What are some of the advantages and disadvantages of intermittent sand-filters
Advantages •Effective at reducing BOD and suspended solids •Low energy requirements •Construction costs are low •Can be unobtrusive Operation •Large areas of land are often required •High maintenance is required to keep the filters clean •Only works well on small volumes •Costs could be high if correct sand and aggregate is not available
What are some of the advantages and disadvantages of drip irrigation?
Advantages •No odours, •Less potential for flooding (compared to non-drip systems) •Less pollution (particularly nitrogen)to underground. •Efficient watering system (less volume required) Disadvantages •Emitters can be clogged, affecting the uniformity of application -difficult to monitor and fix. •Not suitable to use drip irrigation during plant germination period. •Potential problems when applying to frozen ground.
What are some of the advantages and disadvantages of waste incineration?
Advantages: •Wastevolume reduction, •(for waste to energy) Energy recovery, •Lower greenhouse gas emission than landfills (with or without biogas recovery), •Maybe sited close to MSW source. •Less land required *Environmental issues:* •Potentially toxic air emissions (including greenhouse gases) •Can be difficult to dispose of ash (with potentially concentrated contaminants) •Can be difficult to transport and handle ash •(for waste to energy) May be a disincentive to waste reduction and recycling
What are some of the sources of contamination for surface water?
Agricultural runoff (pesticides and fertilisers) • Industry discharges including sewage • Land development (soil runoff) • Waste dumping • Water users (e.g. boat users)
What is disinfection?
Disinfection is necessary to destroy or inactivate pathogenic organisms (organisms that cause disease). It destroys Bacterial, Viral, Protozoan organisms. There are three main methods for disinfection used in NZ: -Chlorination -Ozonisation -Ultra Violet radiation
What is an absorption trench or bed?
An absorption trench or bed comprises an excavated area, surrounded in a geotextile cloth, filled with a gravel / aggregate and housing a perforated pipe. The trench or bed is covered with topsoil. Effluent (can be from primary and/or secondary treated processes) flows into the trench through perforated pipes. The effluent flows into the aggregate surround and then absorbs into the surrounding soils. Local soils must have good absorption.
What are Public Health Risk Management Plans (PHRMP)?
As discussed, the Health (Drinking Water) Amendment Act 2007 takes a risk management approach • Water suppliers need to establish PHRMP to avoid water contamination events • PHRMP's need to consider all parts of a water delivery system • PHRMP identifies the risks (and respective priorities), the resultant effects, monitoring requirements (performance assessment), emergency responses (contingency plans), risk mitigation
How can phosphorus effect wastewater?
As for nitrogen, phosphorous is essential for algal growth and biological organisms. In high concentrations it can contribute to noxious algal blooms. Which can be toxic to humans. Municipal wastewaters typically contain 4-12mg/L.
What is BOD?
BOD is a commonly used parameter to describe the characteristics of wastewater and to determine the effectiveness of treatment. BOD is the quantity of oxygen used by a mixed population of microorganisms in aerobic oxidation (of organic matter) at 20°+/-1°C in an air incubator or water bath. The standard test is 5 days.
How are pathogens detected in wastewater?
Because there are many different types of pathogens it is difficult to isolate, test and identify them, so an indicator organisms is used (similar to E Coli in drinking water testing). The indicator is the Coliform Organism.
How are biosolids treated?
Biosolids may need additional treatment to remove pathogens, depending on final use (e.g. landfill vs land application) *Aerobic digestion* •Originally developed to stabilise activated sludge waste. •Sludge is placed in aerated holding tank for a defined length of time. •Resultant sludge is hard to gravity thicken. Therefore typical disposal method are liquid spreading on farmland, lagooning and drying on sand beds. *Anaerobic digestion* •Sludge digestion turns bulky odorous sludges to inert material that can be readily dewatered. •Digestion without oxygen •Sludge is first broken into organic acids, with by-products of carbon dioxide, methane and hydrogen sulfide by facultative bacteria. •Second, organic acids are broken- down into methane and carbon dioxide by anaerobic acid-splitting, methane-forming bacteria. •The process can become unstable from too much acid, changes in pH or temperature, presence of toxic substance. •Typically monitoring includes volatile solids loading, total gas production, volatile acids concentration in digester sludge and percentage of carbon dioxide in gas.
What is chemical oxygen demand?
COD is a measure of the oxygen equivalent of the organic material in wastewater that can be oxidised chemically by dichromate in an acid solution.
What are some emergency responses under a (PHRMP) to an emergency?
Carry out a rapid damage assessment • Provision of alternate water supply (e.g. tankers) • Provision of additional water treatment (e.g. disinfection) • Posting of public health notices (e.g. boil water notices) • Repair of damage
What does chlorine dose depend on?
Chlorine dose depends on the desired residual chlorine concentration and the degree of treatment the water demands (depends on water quality and needs to be determined through laboratory testing). This is called the chlorine demand. The chlorine demand will change over time as water quality changes. The does also depends on the time the chlorine has to react with the organisms in the water. Generally a minimum of 30 minutes is required. This is called the contact time.
What is free chlorine and how is it measured?
Chlorine is one of the most effective disinfectants and is quite commonly used for water disinfection. Measuring free available chlorine indicates the amount of chlorine available to treat contaminants that enter the distribution system. Referee method is a ferrous ammonium sulphate titration, APHA 4500-Cl F (2005) The test will show a colour change due to a reaction of the chlorine with the ammonium
What is coliform bacteria?
Coliform bacteria are present in human wastes and in soil contaminated with human wastes. These bacteria in human wastes are known as faecal coliform bacteria. Those in the soil are called non-faecal coliforms. Both faecal and non-faecal coliforms are called the total coliform group. This group is used as an indicator of the presence of human wastes in water and the possible presence of waterborne pathogens. The two most common techniques for testing coliform bacteria are the membrane filter technique and the multiple tube fermentation/most probable number technique
What affects the efficiency of chlorine?
Contact time. pH of water. Turbidity of water. Temperature.
What determines the frequency of testing for E. coli under the NZDWS?
E. coli sampling frequency depends on: 1. Nature of disinfection process 2. Whether disinfection monitoring is continuous or not 3. Number of people being supplied 4. Testing location (at plant, in distribution system, at point of use) 5. Secure status of the groundwater
How can compliance for cyanotoxins be reached under the DWSNZ?
Cyanotoxins are seasonal, can increase rapidly and have acute (potentially fatal health risks) Preventing algal bloom is the best defence. However, catchment control (to control nutrient loading) is often out of a water suppliers control. *Monitoring includes:* • Algal cell counts • Chlorophyll concentration • Nutrient concentrations • Water temperature and appearance of scum
What are the priorities set by the DWSNZ?
Determinands whose presence in a water supply can lead to rapid and major outbreaks of illness. These are: 1. E coli 2. Protozoa (Cryptosporidium and Giardia) 2. Determinands of public health significance in a supply or distribution zone that exceed 50% MAV or for micro-organisms are at levels which present an unacceptable health risk. Priority 2 determinands are assigned to each water supplier depending on the water source, catchment, treatment processes and distribution system. 3. Determinands which may be monitored from time to time to see if they should be elevated to priority 2 (chemical and radiological determinands which occur at greater than 50% MAV, micro-organisms, aesthetic determinands) 4. Determinands that are unlikely to be present in a particular supply
How do stabilisation ponds work?
Facultative •Aerobic (with oxygen) and anaerobic (without oxygen) zones •Waste organics in suspension are broken down by bacteria, releasing nitrogen, phosphorous and carbon dioxide. •Algae use these inorganic compounds, plus sunlight, to grow. Growth results in the release of oxygen. •Settleable solids decompose under anaerobic conditions. •Odorous compounds are released during sludge decomposition (hydrogen sulfideand organic acids) but the latter are generally oxidised before entering atmosphere. •Cold weather can reduce decomposition and algal growth which can lead to waste organics build-up and odours during spring thaw. •Typically use two or more shallow ponds with overflow outlet structures , central inflow discharges •Shallow side slopes (able to be mowed), with some rip-rap for tide action. •Ponds are bentonite clay or plastic-lined to prevent groundwater pollution.
What are the four main types of solids in a liquid
Floating matter (e.g. rags, leaves etc) [usually removed early] Settleable matter (e.g. grit, sand) Colloidal matter (e.g. silts, clays) Matter in solution
What is involved in preliminary treatment?
Flow measurement Screening (to protect pumps) Pumping Grit removal (reduces abrasive wear and tear on equipment and sediment build-up in tanks.
What are Volatile organic compounds?
Generally VOCs are compounds with boiling point lower than 100°C and a vapour pressure greater than 1mm Hg at 25°C. e.g. Benzene, bromoform, chlorobenzene, chloromethane, toluene, tetrachloroethene, tricloroethene, vinyl chloride. *These are of concern because:* When in vapour state they are mobile and could be released to the atmosphere They may cause public health risk in confined spaces They contribute to increased reactive hydrocarbons in the atmosphere
What is infiltration?
Groundwater entering the system.
What are guideline values for the Drinking water quality standards in NZ?
Guideline Values (GVs) are factors which affect the aesthetics or appeal of water. For example: • Taste • Odour • Appearance *These are not a legal requirement but are something that suppliers may want to monitor for consumer satisfaction.*
How is bacteria tested for?
Heterotrophic or Standard Plate Count (HPC) gives the total count of almost all types of bacteria in the water sample that can grow on a general medium called the standard plate count agar or nutrient agar. A count less than 500 colonies/mL of the sample means that the water is properly disinfected, and vice versa. Furthermore, a count of higher than 500 colonies/mL interferes with the growth of total coliform bacteria.
What is chlorination?
Inactivates bacteria, viruses, protozoan and Giardia (it does not inactivate Cryptosporidium) (can also be used for taste and odour control. It is the only disinfectant used in NZ that allows a residual to remain after treatment to protect water during distribution. Chlorine effectiveness is dependent on: When chlorine is applied Turbidity Consumption of chlorine by metallic compounds Reaction of chlorine with ammonia compounds Free residual concentration (C in mg/L) (WHO guide level is 0.5mg/L) Contact time (t in minutes) pH (lower pH enhance disinfection) Water temperature (low temperature delays disinfection) The number of coliforms present
What is ultraviolet radiation?
Inactivates protozoa and bacteria with wave lengths. Damages bacterias DNA. Effectiveness dependant on turbidity.
How can metals effect wastewater?
Metal are found in most water sources. They are priority pollutants but are also often necessary for biological growth. If metal concentrations are too high, this may mean they are toxic and/or unsuitable for beneficial reuse options.
What are some of the qualities of groundwater?
Microbiological quality of groundwater is generally better because the microbes are reduced during the percolation process, by filtration, adsorption and natural die-off of organisms. • Less variable (compared to surface water) • Degree of filtration is proportional to the time taken to filter to aquifer • Secure groundwater is sometimes not treated (such as in Christchurch)
Why is a proactive (as apposed to a reactive approach) to water standards a good thing?
Many people may be exposed before a problem is identified, let alone remedied. There is a lag due to the delay in obtaining test results as well as the lag between treatment and distribution/consumption.
What are the characteristics of groundwater quality (DWSNZ)?
Microbiological quality of groundwater is generally better because the microbes are reduced during the percolation process, by filtration, adsorption and natural die-off of organisms. • Less variable (compared to surface water) • Degree of filtration is proportional to the time taken to filter to aquifer • Secure groundwater is sometimes not treated (such as in Christchurch)
What are membrane filters?
Microfiltration (nominal pore size of 0.1μ m) or ultrafiltration (nominal pore size of 0.01μm) Nanofiltration (nominal pore size of0.001μm) or reverse osmosis membranes (nominal pore size of 0.00001μm) can be employed to remove dissolved contaminants (eg in water softening)
What is a major transgression?
Most well managed water supplies will have control limits which will trigger a response before a transgression or non-compliance occurs. A major transgression is an occurance that immediately threatens the safety of the consumers of the drinking water. The Drinking Water Assessor must be notified and measures must be put in place to protect human health. *Major transgressions arise from:* • Excessive concentrations of E Coli (more than 10 per 100ml) • Infectious protozoa or other micro-organisms • Cyanotoxins or chemical determinands at a concentration sufficient to cause acute adverse health effects • The treatment system's inability to disinfect to a level necessary to achieve satisfactory disinfection • The treatment system's inability to provide an adequate barrier to chemical or particles in the water
How can nitrogen effect wastewater?
Nitrogen and phosphorous are necessary for biological growth. Therefore, the level of nitrogen will affect the treatability of wastewater by biological processes. Nitrates can lead to blue-baby syndrome so it excess should be avoided in natural waterways (particularly where drinking water sources are taken from) Nitrogen comprises of ammonia, nitrite, nitrate and organic nitrogen. pH can affect what form nitrogen takes Nitrites can be are easily oxidised.
What are the Carbonaceous oxygen demand and Nitrification oxygen demand curves?
Note that there are two curves-the first is the Carbonaceous oxygen demand curve. The second is a Nitrification oxygen demand curve. This occurs when nitrifying bacteriaexert an oxygen demand-generally this lags behind carbonaceous oxygen demand by 5-7 days
How can odour be treated during wastewater treatment?
Odour is primarily from production of hydrogen-sulfide. Most odours occur at the headworks of the WWTP. Odour control systems include: *Adsorption systems*-e.g. granular activated carbon which adsorbs inorganic and organic compounds. Biological systems-e.g. odorous air can be pumped the activated-sludge system and odours removed through biological processes. *Wet scrubbers*-use of chemically treated water to dissolve odorous compounds. Air is forced up a scrubber tower as chemically treated water (with sodium hydroxide dissolved into sodium hypochlorite) to scrub the liquid.
What are rapid sand filters?
Often two layers of sand overlain by a small layer of coal particles. • Generally operate with 1.5-2m water head on media. • Media type and size and filtration rate depends on incoming water quality. • Large particles get trapped as they pass through (straining) • Other contaminants adsorb to the sand grains. (adsorption) • Homogeneous sand filters downstream of clarifiers tend to be at 6- 12m³/h.m² • Filtration should be limited to 6-7m³/h.m² for removal of Cryptosporidium oocysts and giardia cysts • Filters become less effective over 15 m³/h.m² • Filters are cleaned through backwashing (previously treated water and sometimes air passed up through the filter) - this is an automatic process • Filter effectiveness generally monitored by headloss
What do you need to consider when designing a treatment process?
Population • The higher the population, the greater the potential risk of water borne diseases is. • Treatment for larger populations will be more intensive. Downstream contamination • Potential for downstream contamination e.g. if the distribution network is in poor condition • This will determine whether you need to have downstream treatment capacity (e.g. chlorine residual)
What are some effects from an emergency on drinking water supplies in a New Zealand community
Possible effects *Direct (physical damage):* • Damage to supply (water bores) • Damage to pipe network • Damage to water treatment plant *Indirect (non-physical):* • Change to water source quality • Public health impacts e.g. disease outbreak • Industry impacts (for those relying on potable water) • Economic losses from lost working hours or industry production
How can chlorides effect wastewater?
Presence of chloride can impact on options for effluent reuse. Chloride enters water through human usage. E.g. humans excrete 6g of chlorides per person per day.
What is product stewardship?
Purpose: •To ensure effective reduction, reuse, recycling and recovery of products •To manage environmental harm arising from products when they become waste
What was the purpose of the waste disposal levy fee
Purpose: •To raise revenue to promote and achieve waste minimisation •To recognise the cost of waste disposal on the environment, society and the economy by raising disposal costs •(by-product) to improve the economics of alternative waste management systems (e.g. recycling)
When designing a wastewater treatment plant what do we need to consider?
Quantity and quality of waste water coming in. Sensitivity of receiving environment Disposal options
What are some of the factors that effect recycling within a community?
Recycling will depend on: •Availability of recyclables •Demand for recycled materials / products •Cost of transport •Cost of processing •Quantity (and quality) of recyclables collected
What are the five Rs of waste management
Reduce-use less of-e.g. buy in bulk to reduce packaging quantities Reuse-use something more than once- e.g. using old bread bags to store baking in freezer Recycle-reprocess a material to make something else-e.g. recycled paper Recover-gain energy from the material (without process)-e.g. waste oils refined and used in vehicles. Residual management-final disposal to landfill (solids) or sewer (liquids).
What is coagulation and flocculation?
Removes turbidity, colour, cysts, , oocycsts, bacteria, biological matter, viruses and other organic and industrial substances. Particle removal is first priority but removal of Natural Organic Matter (NOM) is possible. The flocs create a surface for contaminant adsorption. Coagulation is necessary to remove colloidal and suspended solids from water. Colloidal solids are known as non-settleable solids. Range between 1 and 500 Mu (millimircon). Include bacteria, clays and silts. They won't settle out over time. Suspended (settleable) solids will settle but it may take too long - so coagulation makes this process faster.
What is municipal waste collection?
Residents are generally asked to put their waste out in bins or bags provided by the local council. •Waste can be separated into recyclables and non-recyclables; or all waste can be mixed. •Waste is typically collected on a weekly basis. Generally residents pay for this collection service: 1. As a portion of their rates (typically 5%) 2. On a per weight basis (charge per kilogram of waste generated) (currently no city in NZ does this but there are plans to introduce this in some centres).
How does a secondary clarifier work?
Secondary clarifiers are used after biological treatment to collect biological growth. Typical design criteria is similar to primary tanks but typically tanks are deeper, lower overflow rate and weir lengths are longer to prevent overflow of light biological flocs. A greater depth should be allowed for settled solids also.
How does composting stabilize biosolids?
Stabilisation of moist organic solids by natural biological processes when matter is placed in piles with ventilation. •Composting types, include periodically mixed windrows, static aerated pile and enclosed vessel. •Optimum moisture content is 50-60%. •A specific temperature must be maintained for a defined amount of time (e.g. 55°C for 15 days for a windrow operation) •Composting temperature is influenced by moisture content, size and shape of pile, climatic conditions (air temperature and rainfall).
What is the purpose of storage of water in the pre-treatment process?
Storage is often needed to regulate quantity and quality (especially from surface water supply) through treatment plant. • Storage or retention in a slow moving basin can aid water quality through sedimentation (of sand and other particles >0.1mm). Particle removal improves the microbiological quality of the water by removing micro-organisms, in particular Protozoa. Bacteria can adsorb to particles also. • Stratification may occur in deep basins (>20m) which could affect water quality. • Long term storage could cause natural growths if there is high nutrients (N,P) in the water (plants, algae etc) • Storage, depth >10m = reduced plant growth potential
What are some of the tools introduced under the waste minimisation act?
The Act introduced some tools for managing a minimising wastes: •Clearer responsibilities for territorial authorities and requirements for implementing Waste Management and Minimisation Plans (WMMPs) •A levy of $10/tonne (plus GST) for waste disposed to landfill •Central government recognition of product stewardship schemes •The power to make regulations to collection information and to impose standards for various aspects of waste minimisation.
What are the WHO water guidelines?
The WHO guidelines are guidelines and not standards - they provide guideline values and not Maximum accepted values (as in the Drinking Water Standards New Zealand). • They are not legally binding • They provide a scientific starting point for nations or regions as they establish drinking water standards • The guidelines set out a risk-based approach to drinking water standards. This recognises that not all communities have the resources to set rigorous standards for water quality and that some are willing to accept lower quality water. • Nations are encouraged to assess the risk threshold for their water supply. A risk threshold is established by setting a value for Disability-adjusted Life Years (DALY): the acceptable level of health effect measured in years lost in relation to normal life expectancy. The DALY is calculated using the severity of the effects (1-10), the number of people impacted and duration of the effects. The WHO values are calculated on a DALY of 10-6 per person per year. (see page 39 and 40 of the guidelines for more information, if required
How is composting used in waste management?
The compost process involves: 1.Chipping wastes 2.Laying the waste out in long piles or windrows 3.Turning the windrows to maintain aerobic conditions (or blowing air through the piles) Some processes add a mechanised agitation and aeration process before laying the material in windrows to stimulate compost process. This can also help to control odours. Normally, composting processes controlled must maintain a certain temperature (40-50°C) for 3 or more days to ensure any pathogens or disease-capable micro-organisms present are killed.
How is chlorine added to a water system?
The simplest way to add chlorine is through a hypochlorinator. A pump draws hypochlorite solution out and pumps it into the water to be treated. The amount of chlorine entering the system can be altered by either changing the speed of the pump motor or changing the concentration of the hypochlorite solution.
What are some things that must be considered when designing a biological trickling filter?
The size of the biological filter is dependent on the BOD loading (g/day) in the wastewater coming from the primary treatment. Flow (or hydraulic loading rate) through the filter must be fast enough to avoid blocking and creation of anaerobic conditions and must be slow enough so that the water has time to be biological treated by the microbes living on the media. Sometimes some of the treated effluent from the biological trickling filter is recirculated back through the filter to increase the biological treatment capacity of the filter.
What are total solids (TS)
The total solids are the inorganic constituents (either dissolved or colloidal with diameter 0.001-1μm) in the fluid. TSS is one of the two universally used effluent standards/measures for the assessment of the effectiveness of wastewater treatment. (The other is BOD).
What are the three main ways of collecting waste?
There are three main types of ways to collect recyclables: 1.Collection of source separated recyclables (e.g. different bins for paper, glass, plastic etc) 2.Collection of commingled recyclables (e.g. all recyclables combined in a single bin) 3. Collection of mixed Municipal solid waste (MSW) (e.g. all recyclable and non-recyclable waste together)
What is a wetland or marsh system?
These provide secondary wastewater treatment of domestic wastewater. Water must have undergone primary treatment before entering the wetland. It is a man-made swamp planted with aquatic vegetation such as reeds and rushes. Treatment is achieved through filtration through the root systems and through transpiration. Water that has passed through the wetland can be used for irrigation.
What things can affect the aeration process?
Things that can affect aeration processes: •Rate of oxygen transfer depends on BOD loading and ammonia demand. •Rate of oxygen transfer must also account for peak loadings. •Industrial wastes often create instability in aeration processes due to shock loads of high-strength wastewater by depleting oxygen and (if toxic) affecting microorganism metabolism. •Hydraulic shock loads (high flowrates) can increase overflow rates and can cause the loss of activated sludge needed for recirculation in the system. •Low temperature can also affect treatment effectiveness.
How can alkalinity effect wastewater?
This is a measure of the acid-neutralising capacity. It results from the presence of hydroxide (OH-), carbonates (CO3-2) and bicarbonates (HCO3-) This can help resist changes in pH (pH affects the effectiveness of the treatment capacity).
Why is it important to measure the volume of waste rather than just the weight?
To calculate require landfill space, numbers of trucks for transportation
What are the purpose of transfer stations?
Transfer stations are a common waste management facility for large cities, particularly where the final disposal site is either a long distance from the city or it is not safe to provide public access to the landfill. Kerbside collection trucks deposit their waste at a transfer station and then it is loaded onto different trucks to take to the landfill. Transfer stations are useful for: a)Reducing travelling distances for kerbside collection trucks (to make collection more efficient) b)Allowing waste to be transferred to large, 'cleaner' trucks for travel to disposal facilities c)Providing a place for public to dispose of materials (over and above that collected by kerbside collection) Primarily, transfer stations are provided for waste materials but many offer other services such as recycling and reuse drop-offs and accept source separated materials such as vegetative waste and hardfill.
How is turbidity related to crptosporidium?
Turbid water reduces disinfection efficiency as it can 'hide' bacteria from the disinfectants.
What characteristics of waste-water can effect the treatment process?
Turbidity Colour Temperature Conductivity Density Specific gravity / density / specific weight Odour
How is turbidity tested for?
Turbidity is measured as the amount of scattered light by the suspended particles in the sample. Manual or online turbidimetres complying with ISO 7027, or USEPA Method 180.1, or USEPA Method 10133, or GLI Method 2 (USEPA 1999).
What is turbidity?
Turbidity is the murkiness in the water caused by colloidal (1 to 100 nanometer particles) and other suspended particles, such as clay, sand, silt, organic matter of plant and animal origin, planktons, and other microscopic organisms. The lower the turbidity, the less is the amount of the particulate matter. It means there is less probability of the presence of waterborne pathogens, and the water is safer.
What are coagulants?
Typical coagulants include: Aluminium sulphate (alum) Ferrous sulphate (copperas) Ferric chloride Ferric sulphate When mixed with water, these form positively charged aluminium or iron hydroxide which attract negatively charged colloids. Mixing must be done rapidly - 10-120 secs Chemical dose quantities are determined via experiment with the water being treated.
What is a mound?
Typically these are made of sand and overlay a gravel bed. Effluent is distributed evenly over the mound and then it filters through the sand and into the surrounding (natural) material. Suitable where there is: •Poor draining natural material •Rapidly draining natural material •Shallow soil cover or fissure bedrock (too close to groundwater) •High water table
How does an air drying bed dry biosolids?
Typically: sand beds underlain with gravel and perforated pipe underdrains. •Cleaning dried cake from the sand is laborious and must be done by hand to avoid damage to the sand layer. •Modern drying beds are constructed with concrete. •Drying time largely depends on climate and sludge characteristics such as grease content.
How can higher levels of pathogen removal from biosolids be achieved?
Where higher levels of pathogen removal are needed the following processes can be employed: •Heat drying (sludge is dried and pelletized). •Thermophilic aerobic digestion. •Pastuerisation (sludge is heated).
What is Wholesome water?
Wholesome water is potable water that does not contain or exhibit determinands that exceed the guideline values for aesthetic determinands in the DWSNZ.
What are some of the characteristics of rivers, streams and springs?
Variability in quality - this impacts on water treatment. Quality will change with speed of current and amount of water in river. • Variability in quantity - this impacts water supply • Turbid / high in sediment
What are the four processes of the waste system?
Waste generation Waste collection and transfer waste treatment waste disposal
How can waste be used to generate energy?
Waste to energy and incineration is best suited to wastes with high energy content, low moisture content and low ash content e.g. paper, plastics, textiles, rubber, leather and wood. Incineration processes produce fly ash and bottom ash which must be managed.
What do water treatment processes depend on?
Water quality constituents/detremands idntifying processes to remove contaminants. performing lab testing
What are some examples of risk mitigation activities under a PHRMP?
Water quality monitoring of supply, treatment plant and distribution network • Monitoring of catchment (e.g. change in land use) • Establishment of control limits (trigger levels which indicate when preventative action should be taken) • Regular plant and distribution network maintenance • Public health messaging (to prepare public for home treating of water in emergencies) • Provision of redundancy and/or alternate treatment measures in water treatment plants. • Preparation of PHRMPs!!
what are the four main principles of AS/NZ 1547:2012 (on site treatment)
a)To protect public health b)To maintain and enhance the quality of the environment c)To maintain and enhance community amenity; and d)To protect resources
How can taste and odour be controlled?
activated carbon consumption is generally the most effective taste and odour control treatment. Oxididation can also remove taste and odour compounds.
How can pH effect wastewater?
pH is a measure of hydrogen-ion concentration in a solution. High or low pH (<5 or > 9) is difficult to treat biologically.
What is inflow?
unanticipated additional flows entering the system (eg stormwater overflows, foundation drains etc). Inflow can be detected by smoke tests.
How does a trickling filter work?
wastewater trickled over a bed of crushed rock. Wastewater is treated by contact with dissolved oxygen and microbial growth (bacteria, protozoa and fungi that feed on wastewater) on the filter media (typically 2m deep). Most BOD is removed in upper 2/3rdof filter. Excess microbial growth is removed in secondary clarifier. If flow through filter is not high enough, filter can become blocked, anaerobic and can cause foul odours.
What are the Three main water types?
• *Surface water* - eg, streams, rivers, lakes, or reservoirs • *Groundwater* - water drawn from bores or wells • *Roof Catchment* - rain water collected on roofs and stored for later use.
What are the characteristics of microbiological waterborne contaminants?
• Fast acting • Can multiply in their host • Can spread from person to person • Can cause death *DWSNZ give highest priority to health risks arising from microbial contaminants because they can lead to rapid and major outbreaks of illness.*
What are some of the characteristics of Lakes/Reservoirs water? (Surface Water)
• Filled by rain, runoff (rivers), springs • Uniform year-round quality • Requires less treatment than river water as some pretreatment is done in the reservoir. In particular, sedimentation helps to remove turbidity. • Low turbidity, coliform bacteria and colour • Algae, protozoans can cause taste and odour problems • Temperature layers within lakes can affect quality
How is flocculation achieved?
• Flocculation is when these destabilised particles join together by Van der Waal's forces (hydrogen bonding) • Flocculation can be encouraged through a suitable velocity gradient in the liquid. This can be achieved by mechanical or hydraulic mixing. Velocities of around 0.3 m/s should be maintained - fast enough for particles to join together but slow enough for particles not to break up when they hit each other. • Typical retention time - 10-40minutes
What is surface screening/straining?
• For surface water, screening or straining may be necessary. • Coarse screens (8-10cm openings) can be used to prevent large objects in streams entering the treatment plant. • Smaller screens (6-12mm opening) • Passive (static) or active (moving) • Cleaning and blockages need to be considered.
Why would on site waste water treatment be used?
• Small wastewater flows • Too far or too expensive to join to community wastewater network and treatment • Isolated community (e.g. farming)
What is a membrane biological reactor?
•Activate sludge treatment process can be followed by a tank with microfiltrate membranes (rather than a clarifier) •One advantage of this process (over activated sludge followed by clarifier) is that itdoes not matter if the flocs settle or not. Therefore mixed liquor suspended solids (MLSS) loadings can be higher. •Can achieve 98% removal efficiency of BOD. •Stable process (due to less dependence on a specific F/M ratio) •Smaller size than clarifier option. •Higher operating costs (membrane replacement, energy costs and higher sludge quantities)
How is sludge thickened using gravity?
•Circular settling tank with scraper arms •Thickened sludge is removed from bottom of tank. •Ferric chloride can be added to reduce hydrogen sulfide production (odour) •Coagulant chemicals can also be added. •Achieve 6-8% solids content and 80-95% solids recovery.
How do recirculation sand-filters work?
•Effluent from septic tank is passed through a sand filter. •Effluent from the filter is recirculated through the filter to increase treatment efficiency. •Treated effluent is sent for land disposal.
Why should we bother managing solid waste?
•Public health protection •Aesthetics •Reduce odour •Reduce litter •Reduce pollution •Avoid vectors (flies, mosquitos etc) •Reduce spread of disease •Prevent groundwater pollution •Reduce green house gas emissions (from decomposing waste) •Reduce demand for natural resources (through reduction in waste production) •Long-term sustainability
What are some things that affect the waste stream?
•Rural/urban •Level recycling •Number of people •Density housing (eg yard timmings, self management of waste / composting) •Waste minimisation efforts •Economics of recycling •Seasons, weather •Levels of affluence •Lifestyles •Work patterns-eg use of packaged foods, use of computers. •New products •Other?
What benefits do communities get from reducing waste?
•Save money •Reduce waste to landfill •Reduce need for raw natural resources •Reduce energy to process new materials •Reduce fossil fuel use from waste transportation •Less litter
What are some of the design considerations of wastewater that is to be applied to land?
•The volume of wastewater •Quality of effluent discharge from wastewater treatment unit •The soil profile •The soil properties (e.g. permeability) •Required spacing between irrigation fields/trenches/beds etc •Surface water and groundwater locations •Local climate •Local experience
How does the general on site wastewater treatment process work?
•This process allows for the solids and liquids to separate. •Solids/ sludge stay in the tank and are removed(by pumping and taken to a full scale wastewater treatment plant) every 3-5 years. While the sludge is in the tank it anaerobically decomposes. •Grease floats on top and is also removed periodically. •Liquidsstay in the tank for approximately 2 days and then flow out for further treatment or disposal.
Why is effluent disinfected in the wastewater process?
•To protect public health from harmful pathogens •Wastewater discharges may have fecal coliform limits which need to be met and this may have to be achieved by disinfection.
What is drip irrigation?
•Wastewater can be disposed of to land, which can help in the irrigation of vegetation •Only secondary treated effluent can be applied in this way. •Wastewater is applied to the land slowly through a network of perforated tubes -either above or below ground. •Applying water to plant roots allows for more efficient irrigation (less water lost through evaporation) and increase rate of nutrient absorption (meaning less nitrogen lost to groundwater) •Areal loading rate 3 l / m² / day (or 3mm / day)