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The current need for water reclaim in the carwash business can be easily understood, while the many types of reclaim systems to choose from are a little more involved. Biological reclaim systems recycle wastewater from carwashes, truckwashes and buswashes. It is possible to collect wastewater and make it reusable in a physical/biological way, and do it economically, with very low maintenance.
Wastewater components
Vehicle wash wastewater contains two types of waste: • Biodegradeable constituents (oil, grease, detergents) • Nonbiodegradeable contituents (sand, salts) The former can be broken down by microorganisms in a biological recalim system; the latter require physical reclaim. Therefore, a combination of physical and biological reclaim is a logical consequence.
Micro-organisms
The microorganisms involved in biological reclaim are mostly bacteria, but sometimes fungi, protozoa and small animals can be included in the list. They can all co-exist and work together in cleaning up the wastewater. An important feature of micro-organisms is their ability to adapt to different circumstances and environmental conditions. Every environment on earth has microbiological life – even in vehicle wash water. There will always be microorganisms that are capable of growing in the wastewater – they simply need energy sources. By feeding on the dissolved constituents, they will get thier energy and clean up the waste in the washwater in the process.
Biodegradable compounds
The biodegradeable components of wastewater include detergents in vehicle wash products like shampoos and waxes, as well as oil and grease. All organic compounds, and some inorganic compounds – such as ammonium – can be biodegraded by micro-organisms. There are compounds in wastewater that cannot be biodegraded in an anaerobic (without oxygen) environment – some dyes are an exception – it is possible that they can only be biodegraded under anaerobic conditions. Keep in mind that bacteria are capable to adapt themselves to biodegrading almost anything on this planet; it’s a matter of selection. What we call waste is a potential food source for micro-organisms, so selection will take place in favor of the species that are best capable of degrading certain compounds. They have an advantage over other species that are less adapted.
The bioreactor
To get rid of these wastewater components, a biological reclaim system uses a vessel called a bioreactor. In order for the biodegrading process to work, the vessel needs enough dissolved oxygen for the microorganisms as well as plenty of surface area for them to attach to. This surface area can be created by using packing material, also called biocarriers. The microorganisms in this type of bioreactor will grow in a layer on the packing material, creating what is called the biofilm layer. Dissolved constituents in the washwater will diffuse into the biofilm layer, where the microorganisms will start to biodegrade these compounds. Such a bioreactor is called a submerged packed bed continuous upflow aerobic bioreactor. A continuous flow of water from the bottom to the top of the tank prevents stagnation and helps mixing all constituents in the wastewater, includingthe didssolved oxygen.
How it works
Before the wastewater enters the bioreactor, most of the non-biodegradable components should be removed. A sedimentation tank will take care of sand and sludge and an aeration tank will prevent pit odor and bring up the dissolved oxygen level of the water. The remaining particles will flow through a grinder pump, which cuts the particles that could get through the first pit into small pieces. The water will then flow through hydrocyclones – efficient, low maintenance separators – when the correct size has been chosen. The separated water with particles can be returned to the sedimentation tank, and the clean water, cleared of particles bigger than a selected size (5 microns), will flow into the bioreactor. The bacteria can secrete enzymes there that will break down all kinds of organic compounds, serving as food for the micro-organisms. What remains is water, carbon dioxide and biomass. This biomass will grow in a thin layer on the biocarriers inside the bioreactor, and these bio-films are actually small communities of many different kinds of living creatures, all participating in cleaning up the water. A periodical flush of the bioreactor will take excess biomass out of the bioreactor into the sedimentation pit, where it can settle. Biodegradation will continue so sludge amounts get continuously reduced.
Sensitivity of biological reclaim systems
There are many worries about chemicals used in vehicle cleaning that might kill or inhibit life inside a biological reclaim system. One can say that chemicals that are known to be a health or environmental hazard can also be problematic for micro-organisms. But the adaptive properties of microorganisms are so that most. The danger of self-service carwashes, where people may dump dangerous chemicals, can be minimized not only by a watchful carwash operator or some kind of surveillance, but there’s also the dilution of chemicals because of the sedimentation and aeration pits. The larger the total water volume in the system, the more likely the chance that a biological reclaim system is able to absorb shock loadings. A correct choice of wash chemicals is helpful too. Products that are readily biodegradable are preferred. When using chemicals like ABF or HF there is danger for humans, environment and biological reclaim as well. Chemical manufacturers are willing (and pushed) towards producing more friendly chemicals.
Conclusion
A simple, effective and low maintenance system is possibly where biological reclaim is the preferred choice. All you need to do is make a good analysis of the carwash, truck wash or bus wash, including the total water volume in the system and the type and amount of chemicals used. No filters that need to be replaced, no bad odors, just a regular check of the hydrocyclones, airflow and what you’ll get is not drinking water quality but water that’s effectively reusable in a vehicle wash.