If I ever expand my chapter All about the water supply in Perth, Australia into a full book, here's what I'll put into it. Meanwhile, any writer who would like to tackle the project and use my outline (or parts of it), please go ahead. I may never get to it, and even if I do, two different writers will write very different books, even from the same outline. If the world can absorb 10,000 books about Lincoln, it can absorb two books about the Perth water supply.
Outline for a book about the Perth Water Supply System
Point of the book: to describe the Perth water supply as it is. One purpose: to help the public understand reality and lead to better- informed discussion about the system, improving it, saving water, or adding to supplies.
1. What goes in
How much comes down and what's in it (not just pure water). Measuring rainfall. The catchments need 300mm of rain after the summer before any runoff starts.
Rainfall dropped sharply after 1979.
Catchment areas, losses, evaporation, vegetation, rivers, collecting data.
Dams: watertightness, strength, durability, bellmouth overflows, offtake towers. Explaining the things you see at a dam.
Two types of dams:
1. Pipehead dams. Basically a diversion dam that takes the stream flow, or a lot of it, when the stream is really going.
2. Giant storage dams with billions of litres of water.
Post-tensioning the concrete wall at Canning Dam. $45m project just completed. Drilling holes into the granite under the dam, hooking in anchors with stainless-steel cables on them, and tightening the cables right across the top of the dam.
Perth's shallow groundwater is full of iron and manganese, and sometimes hydrogen sulphide. Little use was made of shallow groundwater, and certainly not for public drinking water for the first 70 years of the last century, mainly because of what's in it. Horrible to drink.
People have put bores into this shallow unconfined aquifer since Perth was founded. (It's also how they used to catch typhoid in the old days -- putting a bore down near someone else's sewage.)
Bores have been used for industrial and private purposes, growing veges or watering gardens. Great numbers of private bores now.
In the 60s and 70s, the Water Corp started using some shallow groundwater and treating it to raise it to drinking standards.
At the turn of the last century, there were a few private bores into a deep artesian aquifer. That water was crystal clear. But it had pretty high dissolved salt: anywhere from 1000mg/L upwards.
This source was totally ignored for public water supply, until after WWII. Everyone realised there was this enormous groundwater resource.
Issue of whether we're mining the groundwater, distinct from taking a sustainable yield that's being replaced by rain. (It hasn't rained much for 28 years. Is that the reason the shallow groundwater levels have gone down?)
It's the view of groundwater experts in Perth that the shallow artesian, the Leederville one, is fed from the surface.
It's a lot harder to do accurate measurements and know what's going on underground than for surface water.
There's a huge underground supply between downtown Busselton and Donnybrook. There's enough water there for 7-8m people.
None of the groundwater we use has been polluted by man. Only the shallow bore water from the coastal plain is polluted, and that's only used privately on gardens.
2. What's in the water at this stage?
Australian drinking water guidelines are different from the rest of the world. All based on natural barriers before you even worry about treatment. Far more sensible approach than the English and US approach (to throw everything at treating the water, which costs billions and it will probably make it safe, but don't even bother to keep it clean in the first place. Which is not only uneconomic but silly.)
The chemicals that get in naturally, depending where the water came from. Once the rain hits the ground, it will pick up anything it can dissolve. If it lands on fertiliser, it can pick up nitrates and phosphates. If it's underground water that flows through a aquifer full of iron and manganese, that will dissolve (the brown stain you see in shallow groundwater).
It may pick up some organic material, microbes, viruses -- not necessarily nasty ones or human-borne. If you've got human pollution, you could get salmonella and maybe typhoid.
Road transport to Kalgoorlie of cyanides and nitrates. They can go over the hills, and have to be monitored.
Living things in water and how they contribute or detract from water quality. (Just mention the storage reservoirs at this point.)
One of the protective barriers is the huge storages in our dams. A marvellous natural purification. Most micro-organisms don't live that long and they're in that giant water storage. It's almost self-purifying.
One of the problems with dams, particularly in warmer climates, can be algae growth in sunlight (also true with service reservoirs, which are shallow concrete reservoirs, if they're not covered).
At the Serpentine or South Dandalup catchments, there's nothing in the forest except the careful Alcoa mining. No people, no farmers. And it's all pretty good.
Mundaring catchment has some farming at the northern end, and the water is still OK for drinking after storage and without treatment (except routine chlorine).
Cryptosporidiosis is almost unheard of around Perth. But the odd giardia specimen has been detected, but not enough to be a worry. Giardia are never in the groundwater, unless it's somehow polluted as it's pumped to the surface.
Chemistry. [List is mainly for crossing out things and highlighting the ones of interest or most importance]. Main chemical and physio-chemical parameters. Acidity, algal toxins, alkalinity, aluminium, ammoniacal compounds, arsenic, asbestos, biochemical oxygen demand, bromide and iodide, calcium, carbon dioxide, chloride, chlorinated solvents, chlorine residual, colour, copper, corrosive quality, cyanide, detergents, disinfection by-products, bromate, chloral hydrate, chlorate and chlorite, chloroacetic acids, chlorophenols, trihalomethanes, nitrites, electrical conductivity and dissolved solids, fluoride, hardness, hydrocarbons, iron, lead, magnesium, manganese, nitrate and nitrite, organic matter and chemical oxygen demand, organic micropollutants, pesticides, pH, phenols, phosphates, polynuclear aromatic hydrocarbons, potassium, radioactive substances, silica, silver, sodium, sulphates, suspended solids, taste and odour, turbidity, zinc.
Water microbiology. Bacterial diseases.. cholera, salmonella, typhoid, bacillary dysentery, leptospirosis, legionella, campylobacteriosis, pseudomononas, protozoal diseases, amoebic dysentery, giardia. Viruses... polio, hep A & E. Coliforms as an indicator of bacteriological pollution. Decaying vegetation, moulds, iron and sulphur bacteria, iron, industrial wastes. [What is done about all this comes in the next chapter.]
Chemistry. [Again, the list is mainly for crossing out things and highlighting the ones of interest or most importance]. Main chemical and physio-chemical parameters. Acidity, algal toxins, alkalinity, aluminium, ammoniacal compounds, arsenic, asbestos, biochemical oxygen demand, bromide and iodide, calcium, carbon dioxide, chloride, chlorinated solvents, chlorine residual, colour, copper, corrosive quality, cyanide, detergents, disinfection by-products, bromate, chloral hydrate, chlorate and chlorite, chloroacetic acids, chlorophenols, trihalomethanes, nitrites, electrical conductivity and dissolved solids, fluoride, hardness, hydrocarbons, iron, lead, magnesium, manganese, nitrate and nitrite, organic matter and chemical oxygen demand, organic micropollutants, pesticides, pH, phenols, phosphates, polynuclear aromatic hydrocarbons, potassium, radioactive substances, silica, silver, sodium, sulphates, suspended solids, taste and odour, turbidity, zinc.
Deep groundwater (aquifers)
Very clean water. But has some salt in it.
3. Treating the water
Checks at the source works, bacteriological and viral testing, chemical testing.
Chlorine is used to disinfect the water coming out of the dams and to protect the water in its long journey (both in distance and time) through the mains, the local service reservoir, the pump station and reticulation to the users. It can be days before the water gets to the houses. It will come in contact with micro-organisms that inevitably will get into the pipes, or from the air at the reservoir. Must use chlorine, even if the water doesn't need other treatment or even if it's been through the most elaborate treatment plant -- desalinated or gone through a membrane and comes out as pure as distilled water. Unless it's going to be drunk 100 metres up the road, it needs chlorination. Perth is a low-density city, miles of water mains, so chlorine is needed to keep the water disinfected as it slowly travels.
Where the chlorine is put in, how it works. What affects how well it works (turbidity, metallic compounds, reaction with ammonia compounds and organic matter, water temperature, pH, number of coliforms, contact time). Production of trihalomethanes and the compromises there.
For the Mundaring dam, the Water Corp uses chloranimation: chlorine and ammonia together, that forms a complex which makes the residual last longer.
In the early days, the service reservoir tanks were all open. That was OK then, because the air in Perth was so pure. But there was some post-chlorination done at the outlet of each. But then higher bacteria counts started showing up, mainly because of seagulls. They flew to the new rubbish dumps and then washed in the nearest service reservoir. So we had to cover the service reservoirs (which most big cities have to do anyway, because of air pollution).
Still a hot topic. A lot of complaining letters to politicians and Health Dept.
Fluoridation is a govt decision, required as a health measure for teeth. Strictly controlled. Not allowed to exceed 1.5mgm/L, but the teeth dose is meant to be 0.9. Water Corp dose to an envelope of .7 to 1. Amazing how accurate it comes up in the thousands of samples taken every day.
Bunbury didn't get fluoridation. Still hasn't, after 30 years, so serves as a dental comparison. (Fluoridation works.)
For the shallow groundwater, the treatment is conventional for getting out iron, manganese, hydrogen sulphide. Aerated and a bit of chlorine put in as soon as the water comes out of the ground. That gets rid of the sulphide and helps condition the iron to make it easier to precipitate in the sedimentation tanks. Basically simple standard treatment: screening, straining, settling, grit tanks, flocculation, clarifiers, iron coagulants, pressure filters, anthracite media. Chemical dosing (lime for pH correction). What is put in, at what stage, and what it's for.
What wasn't around until 20 years ago is membrane treatment... reverse osmosis and micro-filters. Really a different type of treatment, although when you think about it, it's really a finer strainer than sand and anthracite filter. Have to apply pressure and use a lot of energy but it means you can get dissolved material out without adding chemicals (instead of tipping chemicals in to make something flocculate and react).
Started using these new methods at Wanneroo. Put in a world-first plant there in Aug 2002, using ion-exchange, to get out the dissolved organic material that occurs naturally in the groundwater. Water Corp found a chemical that no one else in the world has ever found. Took 21 years of research. Finally isolated dimethaltrisulphite. It forms in the slimes of the water mains and causes a nasty smell of boiled cabbage.
How Perth's water chemistry and bacteriological quality compares with WHO standards.
There are some little Water Corp desalination plants in places like Dongara or Merredin. The Dongara one uses seawater and some of the others use brackish water. Straight membrane desalination. Every other farm has a private one now, probably costing about $10/kl for their water.
Water Corp may build a big desalination plant eventually. The price of water would go up a bit -- obviously, if some of it is costing $1.50/kL and a lot of it is still costing 30c/kL.
Arabs have been into desalination for years. Their standard water supply.
4. Getting it to the users
Perth has lots of small water sources, all our dams are relatively small, and we have it mixed up with this groundwater down in the coastal plain -- and the water from this has to be pumped into the system, as distinct from gravitating.
The surface water collected in the hills finds its way down to the city by gravity. All sorts of things could go wrong: the dams are a long way away, water mains can burst. So there has to be some day-to-day storage close to the houses. That's what the service reservoirs do.
What sort are used, about how many, where they are. Covering and protecting them. Finding leaks.
If a trunk main bursts, the service reservoir gives two or three days supply at average flow. At peak flow in summer without water restrictions, it might only be about a day. They are kept full. Filled up at night, unless they're being cleaned.
The service reservoirs are fed by trunk mains -- a big pipe, whether gravity-fed or pumped. And the service reservoirs feed into the reticulation, the pipes that go to the customers. Everything downstream of the service reservoir is called 'reticulation'. And everything upstream is called the 'trunk'.
The groundwater plants are a lot closer to users than the dams. So the service reservoirs, which are fed mainly by dams, are placed to be most economic for water to be pumped into them from groundwater sources, when necessary.
Water Corp has to supply water to the public at a usable pressure. For houses on top of hills, it means a high-level tank, which is just a small service reservoir.
Pipe sizes and types, starting with the biggest.
Types of pipes used (iron, steel, polyethylene, PVC, GRP, concrete, asbestos cement, galvanised iron, copper.). External and internal coatings. Cathodic protection. Laying pipes and testing them. Aftergrowth in the mains. Cleaning. Bacteria and biofilms resistant to controls. How treated and monitored. Where the valves are typically and when they're used. Measuring flows. Some is lost, leakage: how that's detected, how much there is, what is done about it.
Iron and steel for the big pipes. Plastic for the little mains. Plenty of concrete used, mainly for lining. The two main steel trunk mains from Serpentine are now 40 years old and giving worries.
Causes of corrosion, and preventing it. Cavitation, electrochemical corrosion, bacterial (sulphate reducing and iron bacteria).
Pumps. Types and sizes of pumps. Driven by electricity. Plenty of pumping in Perth, because of all the groundwater.
Instrumentation. What can be told about the state of the system from computer screens.
5. Who the users are
Agriculture, industry, domestic, all broken down into further categories, including wastage. How water meters work.
Most people don't understand that the farmers and irrigators are using 88% of the water. Perth is concerned, the only irrigation that directly affects us is all the dams in the southwest between Pinjarra and Bunbury -- irrigation dams, run by Water Corp. Those could be diverted into city supplies (Bunbury or Mandurah or Perth, using the pipeline all the way down the Harvey) if the irrigators didn't use so much.
6. Keeping the system running
Typical servicing problems and how they're dealt with.
The amount of water you lose in flushing mains is small -- two or three peak days supply. The public can't understand the numbers. They just glaze over and say they saw water coming out of a three-foot diameter pipe, pouring down the drain. They see what seems like billions of gallons of water going away. But it's the only way to flush the mains. Should flush the trunk mains and the reticulation about every third year -- to keep them clean, get all the mud and growth out, that gets in despite the water treatment.
Small service requirements by customers, typical call-outs.
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