Industrial wastewater discharge includes pressure piping and open channels, pressureless pipelines and other forms of non-pressure discharge.The sewage flow meter discharged in the form of a pressure pipe is convenient to measure, and can be measured by a pipe flow meter such as an electromagnetic type, a laser type, or a venturi differential pressure type. At present, the sewage discharge in China mainly adopts the form of discharge without pressure open channel, and the sewage open channel flow meter is designed to solve the problem of sewage measurement in this form of discharge.
1. Working principle and composition of open channel flow meter
Pasteur trough and thin-walled weir are commonly used as measurement methods for open channel sewage flow.Its principle belongs to the throttling flow measurement technology. The direct object of measurement is the water level difference between upstream and downstream of the throttling device. According to the water level difference, the instantaneous flow on the cross section can be calculated.
The open channel sewage flow meter is composed of a measuring weir (flow measuring flume), liquid level sensor and secondary instrument. The work of forming the head (standard flow), measuring the height of water level and calculating the flow rate are completed respectively.
2. Types and scope of weirs and troughs
Water-measuring weir
A weir is a device that intercepts the flow of water and allows it to overflow from the top. There are many kinds of weirs: According to the thickness, it can be divided into thin-walled weirs (whose thickness is less than 0.67 times the geometric head), suitable weirs and wide-crested weirs, etc.According to the cross-section shape, it can be divided into triangular weir, trapezoidal weir, equal-width weir, etc. According to the connection form of jet and downstream water level, it can be divided into submerged weir and non-submerged weir.Thin wall triangular weir, thin walled trapezoidal weir and thin wall rectangular weir are commonly used.Under certain conditions, for a certain thin-walled weir, the flow rate has a certain function relationship with the geometric head height, and the sewage flow can be measured accordingly. When measuring the flow with water weir, the loss of water head is large, which is suitable for measuring the sewage with little suspended substance and non-fibrous substance.
Flow-measuring flume
Wide-crested weir with lateral contraction is called flume when the height of weir bar is zero. It is a special deformation of weir. It can be divided into short throat flume (Pasteur flume), no throat flume (Sun flume) and long throat flume.Commonly used in open channel sewage flow metering is Pasteur trough.Under certain conditions, for a certain Pasteur trough,there is a certain functional relationship between the flow and the upstream water level height,according to which the sewage flow can be measured. When measuring flow with flow measuring trough, head loss is small and water quality conditions are wide. When measuring sewage, aquatic organisms on the trough wall should be cleaned up in time to keep the trough wall smooth.
3. Liquid level sensor
There are mainly ultrasonic liquid level sensors, pressure type liquid level sensors, capacitive liquid level sensors, float type liquid level sensors and so on.These level sensors have their own characteristics and different application ranges.
Ultrasonic sensor is a specific application of ultrasonic ranging method. Its characteristics are to achieve non contact flow and wide application range, but the required liquid is reflected well by ultrasonic wave. If there is abnormal reflection of foam, debris and biological mud, it will bring greater error. In addition, ultrasound is also affected by weather factors such as temperature, air pressure and wind speed. Although these factors can be compensated, the structure of the instrument is complex and the cost is high.
The characteristic of pressure type liquid level sensor is simple installation. However, the specific gravity of the tested liquid is basically constant, so its application in sewage with large variation of specific gravity is limited. In addition, attention should be paid to the smooth opening of the pressure measuring hole when used in sewage.
The characteristic of capacitive hydraulic sensor is that there are no moving parts, but the mechanical strength and dielectric properties of insulating medium are difficult to take into account, and the change of capacitance caused by the influence of temperature reduces the measurement accuracy. In addition, the electrode surface should be cleaned up in time when used in sewage.
The float liquid level sensor has the characteristics of low cost, not affected by water quality and wide application range, but it requires that the specific gravity of water body is basically constant, and attention should be paid to the effect of surface adhesives on the specific gravity of float.
4.Secondary instrument
Secondary instrument is an automatic device which can receive the voltage (current) signal of liquid level sensor and accumulate sewage flow based on it. It can not only give instantaneous flow, but also get cumulative flow. It can connect the recorder to observe the change of flow rate and the computer to realize the automatic flow monitoring.
</a> The woman, who asked not to be named, said that the dates on a letter notifying her of the appointment showed that it took almost 20 days for the document to travel via post from Ninewells Hospital to her home address.
</a> Official statistics from the world's second-largest economy showed that Chinese GDP in the third quarter of the year was 7.8pc higher than a year earlier, following stimulus measures and expansionary monetary policy from officials.
</a> Document requests and discussions between the banks andgovernment have picked up recently after Eric Holder, the U.S.attorney-general, indicated publicly that more mortgage-backedsecurity lawsuits were coming by the end of the year, the FTsaid.
</a> Tate & Lyle said the cold weather affected sweetener volumes across the business and that while performance in the second quarter was in line with expectations, it expected adjusted operating profit for the six months to September 30 to be lower compared to the same period last year.
</a> Anna Benson was charged with two counts of aggravated assault and battery with a gun, possession of a firearm in a felony and criminal trespass after she allegedly broke into the home the couple once shared in Smyrna, Ga., Monday.
</a> In one way Fulham have gone downmarket. When Mohamed Al Fayed took over the club 16 years ago he was proprietor of Harrods. The new owner, Shahid Khan, makes car parts. But yesterday it was clear everyone connected with Craven Cottage, from administrators through to the fans, believe that the man with the moustache is just the chap to take over Fulham and lift them to the mythical "next stage" all mid-table Premier League clubs dream of â Champions' League football â while safeguarding the traditions of what the fans like to call "this family club" down by the Thames.
</a> "It would be hard to destabilize this city at this point," said Willie Temple, a pro-British Protestant in Londonderry who became an activist to defend his community at the height of the unrest in the 1970s. "People have seen the benefits of peace."
</a> The pass rush will have their work cut out for them against Roethlisberger, who is renowned for his ability to make something out of nothing when a pocket collapses. âIt doesnât get us out of our game plan,â Sheldon Richardson said. âWeâve still got to rush him, weâve still got to keep in pass rush lanes and try to get to him while he still has the ball.â ⦠WR Santonio Holmes (foot/hamstring) did not practice on Friday and will not play⦠OL Oday Aboushi (knee) was limited at practice and questionable. ⦠Jets LB Troy Davis will be added to active roster, according to a source.
</a> Katy Perry is taking her latex obsession to a whole new level with her ad campaign for the launch of her new perfume, Purr. The sexy singer crawls around in a catsuit in the photos shot by photographer Miles Alridge.
</a> “Labour has increased our membership under Ed Miliband’s leadership. And now Ed Miliband is absolutely determined to keep changing Labour, to open up politics more to the public, and to ensure that Labour is a genuinely One Nation Party that is rooted in every community.
</a> "Now when I try to put a sweater on her, and it goes over her mouth, she starts screaming and screaming," says Carpino. "I know this is because of what happened at the mall. But I don't know what to do about it."
</a> "I'll take anyone," Only said during his speech, his hands sweating. "Old or young, dad or mom, black, white, purple. I don't care. And I would be really appreciative. The best I could be."
</a> Vodafone, which this month agreed the sale of its stake in U.S. operator Verizon Wireless for $130 billion, wants to buy Kabel Deutschland to offer more television and fixed-line services in Germany, its largest European mobile market.
</a> The deal value could vary by 60 million euros either waydepending on the amount of Caixabank real estate assets managedby the newly formed company over the next three years, Caixabanksaid in a statement.
</a> "Were some of the biggest Wall Street firms to fail thisweek... I think it would be very hard for the President and U.S.Treasury Secretary to persuade the Congress to commit taxpayers'money," Tucker told a London School of Economics seminar onTuesday.
</a> "Our acquisition and revitalization of the Forum is a perfect complement to the Madison Square Garden arena," Hank Ratner, MSG president and CEO, said in a statement. "It now allows us to have world-class venues in both New York and Los Angeles, linking the two top entertainment markets in the country."
</a> In rejecting a preliminary injunction, Friedman said there was no need for such an emergency measure because Klemencic has until the end of March to apply for an exemption from Obamacare, by which time the lawsuit may be over.
</a> Suntory Beverage & Food Ltd. (2587) agreed to buy the Lucozade and Ribena drink brands from GlaxoSmithKline Plc (GSK) for 1.35 billion pounds ($2.1 billion) as the Japanese company reduces reliance on its domestic market.
</a> The amended deal calls for the domestic doyenne's company todesign Martha Stewart-branded products for J.C. Penney in windowtreatment, holiday and other categories not claimed by Macy's.Penney also gave up its 17 percent stake in Martha Stewart'scompany.
</a> By diversifying its revenue streams and creating new ones,like the Indian joint venture, Goh and his team plans to reduceSIA's dependence on the flagship carrier over the medium term,say investors and analysts.
</a> An attack last year on a US compound in the city of Benghazi killed four people, including the US ambassador, while a car bomb outside the French embassy in April injured two French guards and a number of residents.
</a> Meddling with our voting system is not going to fix our (broken) political system because the problem is the venal and corrupt culture that exists within our establishment political classes and whilst they remain dominant nothing will change. Changing the voting system is no more than shuffling the deckchairs on the Titanic…..
</a> ** British soft drinks maker Britvic sounded lessthan enthusiastic about the prospect of resurrecting a mergerwith smaller rival A.G. Barr after the proposed deal wasofficially cleared by the competition watchdog on Tuesday.
</a> (c) I get everything I need online and have not had any problems. Viagra costs a fortune from a chemist. I can get 50 blue pills online for £25 and I’ve not had any complaints, if you know what I mean
</a> People may criticize Obama for his attitude, but please remember that Obama is a Constitutional lawyer and reads Article I, Section 8 in all parts dealing with the powers of Congress as only a Constitutional lawyer would do. It’s up to Congress. That’s what the framers said and that’s what people who know the Constitution say. The problem is that we “Want Daddy to solve our problems.”
</a> âWe try to preserve the stories in these vehicles,â Stark said, as he sat in one of the classic muscle cars. âSo in this Caprice, we have air fresheners in the grill. And in that van towards the back, we left the love letters (we found).â
</a> "The biggest driver of change in the behaviours of banks has to come from within the banks themselves - they have to come to a realisation that they will be better businesses commercially and ethically if they change their behaviour.
</a> âI understand (why people are worried),â Brown said. âBut we worked hard this offseason and weâre excited about the opportunity we have and weâre ready to go out there and just show what weâve got, show that weâre effective backs and we can be efficient in this offense.
</a> Thurman introduced his teammates around Los Angeles. In those years, the Cowboys hosted training camp at Cal Lutheran College in Thousand Oaks, Calif. Thurman, the local product, knew where all the parties were, and curfew was no deterrent. Players parked cars across the field from the dorms and sneaked out the back.
</a> The Google-owned phone maker has added a new iPhone migration tool to its Moto X setup system, letting you easily transfer your contacts and calendar from your Apple smartphone to a new Moto X. After customizing your Moto X on the MotoMaker website and placing your order, you'll see a confirmation page inviting you to use the new migration tool.
</a> Looking beyond the Fed, market participants had an eye onthe looming budget and debt limit debates in Washington. TheWhite House said Wednesday the latest Republican proposal movesaway from compromise.
</a> Households and businesses have been told not to expect interest rate rises for at least the next three years as Mr Carney said rates will remain at 0.5% until the unemployment rate drops to 7%, depending on stable inflation.
</a> Foxconn has come under fire in recent years for workingconditions in its factories in China, which employ 1.2 millionpeople to mass produce electronics components and gadgets suchas iPads and iPhones.
</a> Dr. James Spencer, a dermatologist in St. Petersburg, Fla., and a board member for the American Academy of Dermatology, says that for those who are very sun sensitive, a white cotton T-shirt will likely not provide enough protection. Instead, Spencer recommends finding a shirt in a tighter weave or washing clothes with a sun protection rinse such as SunGuard wash, which claims to make clothes have a UPF of 30.
</a> Mira Calton, nutritionist and co-author of the book, Rich Food, Poor Food, said freezing a product prior to delivery would "most likely require additional preservatives and dough strengtheners being added to the recipes."
</a> Lew, who visited Beijing shortly after Xi and a new cabinet led by Premier Li Keqiang took office, said he detected signs that some changes advocated by the United States were gaining traction in Beijing.
</a> Greece's descent into a deep economic crisis has triggered public anger against a political and business elite widely viewed as privileged and corrupt, prompting prosecutors to step up investigations into corruption cases.
</a> "Republicans have said that this would be a big jobs generator," he told the paper. "There is no evidence that that's true. The most realistic estimates are this might create maybe 2,000 jobs during the construction of the pipeline, which might take a year or two, and then after that we're talking about somewhere between 50 and 100 jobs in an economy of 150 million working people."
</a> "This is not a case where there's an emergency right now, and because conservatorships of the person and estate involve liberty and property interests, there are a lot of t's we need to cross and i's we need to dot."
</a> At a launch event on the morning of Monday 22nd July, regional farming and food industry leaders will join Norfolk MP George Freeman, Chairman of the All Party Group on Agricultural Science, and the Government's Adviser on Life Science, to launch the Strategy. Mr Freeman is calling the strategy a 'green revolution.'
</a> A half-baked design could be overlooked if the Gear actually did something useful, but at this point there’s not much I can point to. Doing just about everything on the Gear takes several swipes, and while it’s nice to see message notifications on your wrist, I didn’t find it to be much more convenient than pulling my phone out of my pocket. In fact making it more difficult to escape notifications could actually end up hampering your productivity (something that we may also see with Google Glass).
</a> "He went peacefully and quickly after just completing this novel, a tale he had pondered while writing columns, campaign books, a memoir and covering our politics and politicians," his wife, Alice, said in a note to his colleagues, according to The Associated Press.
</a> The rush of support from Wall Street analysts is a remarkable shift from the days after the initial public offering in May 2012. Shares wound up losing about half their value from the $38-a-share offering price, as Wall Street analysts and investors turned sour on the company's prospects with mobile ads.
</a> BEIJING/HONG KONG - China reiterated its opposition on Thursday to a European Union plan to limit airline carbon dioxide emissions and called for talks to resolve the issue a day after its major airlines refused to pay any carbon costs under the new law.
</a> Even though Kaiser provided Collins with 15 pages of transcripts of the online chats, Collins never pursued the matter. After the issue became public, Silver said Collins never alerted him to the situation at the time and that he first heard about it in June, after it was brought to his attention by Assemblywoman Deborah Glick (D-Manhattan).
</a> "It has blasted the way open by drastically reducing the single largest cost factor in prices, namely the MTR, which both Vodacom and MTN enjoy," said Alan Knott-Craig, chief executive at privately owned No. 3 mobile operator Cell C.
</a> “(The accusers) are miserable and wretched not only because of their brazen lies and slander but because they are exploiting a tragic event for politicking, to win votes and to divide Greek society,” the party said in a statement.
</a> Tanden added: "And as the first woman to run the Fed, Janet is breaking yet another glass ceiling in an arena full of gender barriers. Because of her leadership, determination, and courage, more little girls around the world can dream of some day running economies."
</a> NASA, meanwhile, has suspended all U.S. spacewalks while the investigation into last month's near-drowning continues. An Italian astronaut's helmet filled with water during a spacewalk on July 16. He barely made it back inside. The water is believed to have originated from the suit's cooling system.
</a> Although I welcome most forms of rehabilitation to help convicts back into society, I'm not sure if this is the right time to do this when we have a large number of unemployed looking for work. If this is a form of cheap labour then this should not be encouraged. Why not provide them with courses run by a college or enrol them on the Open University?