Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.

Категории

Биотехнологии Usage of immobilized cells of microorganisms in aerotanks - displacers with the application of glass go-devil
просмотров - 217

Lectures 10-11

The immobilized whole cell system is an alternative to enzyme immobilization. Unlike enzyme immobilization, where the enzyme is attached to a solid support (such as calcium alginate), in immobilized whole cell systems, the target cell is immobilized. Such methods may be implemented when the enzymes required are difficult or expensive to extract, an example being intracellular enzymes. Also, if a series of enzymes are required in the reaction; whole cell immobilization may be used for convenience.This is only done on a commercial basis when the need for the product is more justified.

Water gardens create a serene atmosphere and create a natural setting with its pond-like waters and aquatic plant life. In order to recreate the biological system that makes up a natural pond, a little help is needed. The natural biological filter is bacteria that break down animal waste and turn it into less harmful by-products that can be absorbed by plants as food. Specifically, animals excrete ammonia. Bacteria break down the ammonia first to nitrites. This is another harmful biochemical to plants and fish until it is broken down further by the bacteria to nitrates. It's in this form that plants absorb it as food. A biological pond filter adds bacteria to the pond and provides a surface for them to call home.

If your water garden will house fish you need a biological pond filter. Think of the biological pond filter as a waste facility. It provides all of the tools necessary to collect the garbage and process it so it doesn't harm the fish life in the pond.

You can either buy a biological pond filter that includes all of the components necessary to clean the water or build one yourself. A biological pond filter must do two things: house the bacteria and make contact with the water in the pond. The type of filtration system you use depends first on the size of your pond. Water gardens that are smaller than 1,200 gallons can use a submersible, all-in-one system. Large water gardens need a larger filtration system often including several chambers to process all of the water and waste. For both sizes, water enters in the top, controlled by a pump, passes down through a filter to remove debris, then down through the bacteria and out the bottom into the main body of water.

The key to a biological pond filter is the medium used to house the bacteria. It must be something that won't affect the water chemistry. Materials that are best suited for this purpose are made of mineral compounds like clays, glass, and carbon granules like lava rock, or a plastic like cut up pieces of corrugated pipe.

Waste and vent pipes usually are the same pipe, with wastewater flowing downward and gases rising in the pipe. A 3- or 4-inch vertical pipe serves as the main stack to carry wastes, water vapor and gases from the house. The main stack also acts as a vent for gases that collect in the septic tank. Gas from a septic tank has a bad odor, may cause serious illness, and in some situations, can be explosive. In cold weather, the gases exiting from the stack contain water vapor that will form a frost layer that can get thick enough to close off the end of the stack. Excessive snow on the roof also can block the vent stack. Closing off the vent stack will prevent fixtures from draining properly. The vent stack extending above the roof should be insulated to help prevent frost and snow from closing it off.

A water trap must be installed in the drain line between each fixture and the main stack. The trap prevents sewer gases from coming into the house through the fixtures. Without a vent pipe, a full flow of wastewater in the drain line could siphon water out of the traps and let sewer gases into the house. Sometimes, during very windy conditions, wind pressure on the vent stack can force sewer gas through the trap. Proper venting installed according to the plumbing code will prevent this problem.

Adequate cleanouts are necessary in the stack so the plumbing and sewer line can be serviced and cleaned. One cleanout should be installed at the base of the stack and a second at the point where the sewer line leaves the house. One cleanout may be enough if the stack is near the point where the house sewer leaves the building.

Cast iron or copper drain systems may be found in older homes. Most new homes use plastic sewer pipe listed in the plumbing code. When working in older homes, avoid direct copper to iron pipe connections since pinhole leaks may develop in the iron due to galvanic action. Use insulated connectors between copper and iron pipe to reduce this problem.

House sewer pipe should have a slope between 1 percent and 2 percent. This is around a 1- to 2-inch drop in 8 feet. On too flat a grade, the liquid will slow down, allowing the solids to settle out in the sewer pipe. On too steep a grade, the liquids will flow away from the solids.

The sewer line from the house to the septic tank may be plastic sewer pipe with glued joints or cast iron with stainless steel clamps or leaded joints. If using plastic pipe, the pipe must have a pressure rating equal to Schedule 40 or greater. The joints must be glued so they are watertight and resist root penetration.

The house discharge sewer must be at least 4-inch diameter pipe. This pipe must have a uniform slope with no high or low spots. A common place for frost to accumulate in the house discharge sewer pipe is just after the pipe passes through or under the basement wall. Where the house sewer pipe is above the frost line, this problem can be corrected by putting 2-inch-thick rigid foam insulation over the pipe during the installation process. The rigid foam insulation should extend at least 1 foot on either side of the pipe. Insulation generally is not needed if the house sewer is more than 4 feet below the ground surface.

Don’t make sharp bends in the house sewer system. When 45- or 90-degree bends are necessary, use long sweep (long radius) elbows to allow a plumber’s snake to get through the sewer line. If long sweep elbows are not available, use several 22- and half-degree elbows.

Never, under any circumstances, allow basement footing drains to discharge into the house sewage system. This water will overload the septic system. It can cause the water and sewage to back up into the house. Run basement footing drain water to a sump. Install a sump pump and pump the water out away from the drainfield (picture 5).

Picture 5. Deep septic tank installation. Suitable for use where a high water table is not present. Always check with the tank manufacturer to make sure the tank has the load- bearing capacity to handle the soil overburden.

Control questions: