DE102005035950A1 - Industrial wastewater treatment comprises filtration followed by reverse osmosis, with ultraviolet irradiation before or after reverse osmosis - Google Patents

Abstract

Industrial wastewater treatment comprises filtration followed by reverse osmosis, with ultraviolet irradiation before or after reverse osmosis. An independent claim is also included for wastewater treatment apparatus comprising a Dynasand (RTM) filter followed by a reverse osmosis unit, with a UV unit before or after the reverse osmosis unit.

Description

object The invention relates to a method and a device for cleaning industrial wastewater.

For many Processes in the chemical or pharmaceutical industry size Needed amounts of water, be it as process water, as a component in the chemical conversion or as cooling water. The resulting wastewater are in contrast to municipal waste water / household wastewater chemically contaminated and must before discharge into near-surface waters or in the local Sewage system to be recycled. This is next to the possibly existing Exposure to pollutants frequently also the amount of sewage is a problem.

In the cooling towers chemical Process equipment is becoming common City water used as feedwater. Many cooling water-operated heat exchangers tend therefore for pollution by scale formation, in particular if the water as a cooling medium Temperatures of above 60 or even 70 ° C is exposed. As a result occurs a lower heat transfer and thus often a loss of capacity the production plant. These disadvantages make an increased cleaning effort required,

to Production of demineralized water is the process of reverse osmosis known. In this process, water is pressurized by a pressed semipermeable membrane. The pores of this membrane are corresponding Fine, so that mainly only the water molecules can pass through the membrane. The actual Retention rate the water content is on average about 95%. The Designation reverse osmosis results from the fact that the Water is forced against the osmotic pressure through the membrane So from the lower concentration to the higher. Disadvantage of this procedure is that the membranes are common are very sensitive and can be damaged by pollutants or suspended matter.

task In the present invention, it is a method and an apparatus for cleaning industrial wastewater to provide the amount of sewage discharged into waters will reduce and the authorized discharges for pollutants sustainable fall short, as well as recycle water again in Cooling Systems use to save city water, using the recycle water have a low water hardness intended as city water, so that the cleaning intervals of the flow-through heat exchangers extended can be.

• (A) Filtration
• (B) UV-Bestrahlung und
• (C) Umkehrosmose

wobei die Schritte stets in der Reihenfolge erst A, dann B, dann C, oder erst A, dann C, dann B, vorzugsweise erst A, dann B, dann C durchgeführt werden.The object is achieved by a process for the purification of industrial wastewater and, if necessary, continue to recover, ie for recycling, comprising the steps

• (A) Filtration
• (B) UV irradiation and
• (C) reverse osmosis

wherein the steps always in the order first A, then B, then C, or first A, then C, then B, preferably first A, then B, then C are performed.

The inventive wastewater treatment device has the following system parts: a primary treatment (optional), a Dynasand filter (obligatory), a UV system (compulsory) and a reverse osmosis system (compulsory).

preferred embodiments are the subject of the dependent claims or described below.

sewage For the purposes of the invention is any contaminated chemical wastewater, the has not yet gone through steps (A), (B) and (C). Under Recycle water in the context of the invention is understood to mean such water, that is purified so that it is reused for operational use can be used. The method according to the invention thus comprises wastewater treatment and wastewater recycling.

The inventive method and the device according to the invention are used for the treatment of chemical wastewater to the wastewater volume, in the waters is introduced, and to reduce the amount of pollutants.

To the method according to the invention is in a first section, the chemical waste water may also be mechanically pre-clarified chemically and / or biologically (primary clarification). The primary treatment is optional and may e.g. stay away when the water to be purified, e.g. do not use organic or coarse impurities is. The pre-treated waste water from the primary treatment (O) is supplied via a template (V), preferably with two connected basins, to a filter (A) encouraged the dynasand principle is working.

The waste water passes through the filter horizontally and is then removed from the side of the filter (A). At the same time, the filter sand is constantly being pumped from bottom to top by means of an air-driven mammoth pump circulated. The filter sand is cleaned in a washing device and returned to the filter bed. In this case, a classification of the filter sand takes place so that the wastewater stream to be filtered flows through the filter bed in the direction of decreasing grain size. The preferred filter design is a further development of the classic Dynasand filter and leads to significantly better filter performance. The continuous flushing water flow from the sand cleaning process is introduced into the chemical wastewater system.

The Dynasand filtration removes particulate matter and other particles in the air Range of 5-100 μm. she is necessary for the effectiveness to increase the UV sterilization, so that the residual value to the lowest Level can be maintained. Furthermore, would by the dirt particles the membranes of the reverse osmosis system are damaged.

Of the Filtrate stream leaves the filter with a filterable solids amount of preferably smaller 5 mg / l. The filtrate can be collected in an original basin and be stored. The filtered wastewater becomes a UV system (B) pumped.

Here the wastewater is sterilized by UV radiation. The sterilized water can then safely be used internally and is preferably in relation to a partial flow also used without reverse osmosis.

Out the UV system or the buffer store, the wastewater to the reverse osmosis system (C) promoted. Previously, the water with a turbidity measurement on suspended matter checked out. is the cloudiness too high, the sewage will return for filtration (A) led the Recyclewasseranlage. The turbidity measurement is for protection the membranes of the reverse osmosis plant.

In the reverse osmosis system softens the wastewater. The reverse osmosis system is preferably for the same capacity Water flow as well as the UV filtration designed. That from the reverse osmosis plant Exiting permeate water can be directed to a buffer (PV) become. This is needed, for example, when cleaning times (about 2-3 h) the reverse osmosis system or the UV system are to be bridged. The purified Water can now be used operationally as recycle water become. The concentrate is at least partially discharged from the recycle stream.

by virtue of high quality of the permeate it may be necessary to remove the filtrate before entry in the cooling water system to blend with concentrate to a minimum hardness of the recycle water, as it is for the operational use is required to ensure. Otherwise, can Corrosion take place in the piping systems of the industrial plant. The intersection is preferably decentralized or for everyone single cooling tower (KT) instead. This allows the conductivity in any cooling system be set individually. For blending is about 5 to 30 % By weight of the amount of concentrate required. The concentrate is in stored the concentrate template (KV). Excess amounts of the concentrate can be pressure-controlled dissipated become.

By the method according to the invention, using a reverse osmosis system for softening the cooling tower feed water, the Scale formation reduces and the service life of the heat exchangers elevated become. The reverse osmosis system can be recycled with recycled chemicals operate. Another advantage of this is that the previously in the waters introduced chemical wastewater can be drastically reduced. The use of recycled water can generate a corresponding amount of municipal water (StW) can be saved. By reducing the water hardness in the cooling system can Furthermore, the cleaning intervals of the connected heat exchangers extended become. As another positive side effects occurs the reduction of the Need for hardness stabilizers in the cooling circuit on. These are so far dosed to excessive scale formation too avoid.

1 a flow chart of the plant according to the invention.

Hereinafter, a preferred embodiment of the invention with reference to 1 wherein the method steps described in greater detail are specialties of the more general inventive idea and each of the more detailed method steps can also be placed in the context of the more general description of the invention.

Primary treatment (O) / chemical, mechanical cleaning (optional) In the primary treatment (O), the process waste water / chemical waste water mechanically cleaned. In addition, however, can also be a chemical treatment respectively. Furthermore, it is useful with the help of Flotationsbelüftern and Flocculation aids the water-insoluble impurities largely from the watery Phase separate. The forming sink and flotation sludge becomes then cleared after reaching the drainage strength, or pumped out. Floating liquid oils and fats can be discontinuous be abgeskimmt. Furthermore, the wastewater is neutralized in the primary treatment.

Aeration tank / biological Wastewater treatment (part of primary treatment, optional) part of primary treatment can Aeration basins consisting e.g. from a denitrification stage, a nitrification stage and / or a stage which serves both as denitrification or Nitrification, preferably all three stages. In the Nitrification is e.g. ventilated with a rotary blower. With heavy contamination can also pure oxygen can be added to a better rate of degradation with regard to the carbon or nitrogen compounds. In the drainage area of the aeration tank may be on the way to the secondary sedimentation tank a precipitant added to the colloidally dissolved To bind substances.

To the pre-cleaning step, the TOC (total organic carbon) and TN (total nitrogen) values of wastewater measured using online equipment and the wastewater on storage tanks (V) distributed. The nitrogen-contaminated wastewater from a process plant part is stored in extra tanks. All tanks are preferred with stirrers and upheavals equipped to prevent sedimentation of solids. Furthermore, a certain amount of phosphate can be added to the volume flow become.

Dynasand Filtration - Process Step (A) From the effluent pump of primary clarification (O), the clarified water is pumped to wastewater filter station (A). The depth filter is a continuous sand or gravel filter, which is flowed through horizontally. The flow rate of the pumps is regulated depending on the level of the filter. If the level is sufficient, the flow rate is kept constant at approx. 32 m ³ / h, if the level drops too much, the flow rate is adjusted to ensure a minimum level in the drain pumping station.

Of the Filter sand of the depth filtration is powered by a compressed air Mammoth pump continuously from the lower filter area into one overhead scrubber promoted. In this (Ac), the sand is under discharge of a rinse water washed and then returned to the filter bed. Of the washer has at the same time the function of a classifier, so that the clarified Always water the sand filter from the coarse grain towards the fine grain portion flows through. The filter sand thus travels vertically downwards through the filter (Aa). The resulting rinse water gets out of the sand scrubber introduced as dirty water (SW).

The Filtered water is level regulated by means of a pump of the waste water filter station deducted. In the optional downstream filter (F), which is a backwash filter with metal sieve, possibly entrained filter sand is deposited become. By opening of an automatic valve becomes the dirt zone of the filter (F) rinsed and emptied into the chemical wastewater (SW). The triggering is time-controlled.

The filtrate is monitored by means of a transmission measurement. Indicates the filtrate stream too much cloudiness so it is not put through to the irradiation reactor, but about Valves back spent in the dynasand filter. Too high a solids load, especially in the range above 15 ppm causes a significant Deterioration of microbiological inactivation performance by Partitioning or absorption of UV radiation. If sufficient filtrate the filtrate stream is passed to the UV disinfection system.

UV system (B) - process step (B) With a feed pump of the UV system (B) is the filtered Water is passed to the irradiation reactors. In the reactors will the water by means of UV irradiation sterilized. The UV irradiation system consists of pressure-resistant stainless steel tube reactors with each several in the flow direction lying low pressure mercury vapor lamps. For maintenance and cleaning operations, two reactors were arranged in parallel.

The Reactors can also be operated in series. When sinking wastewater transmission can to ensure the disinfection in serial driving the double UV dose can be introduced.

For monitoring the degerming performance, an intensity measuring device was installed per reactor, which as Summenparameter all intensity-reducing influences such as lamp aging and pollution as well as transmission reduction of the filtered water registered and upon reaching predetermined Limits reports. Set limits for water quality according to EC Directive 75/160.

The respective amount of wastewater is determined by inductive flow measurement recorded and compared with the procedurally permissible. Does that rise? Flow over the permissible Value, then the flow of water, just like in the case of too high downturn diverted into the second basin of the drain pumping station.

Reverse osmosis (C) - demineralization of the sterilized water - process step (C) The filtered and UV-sterilized feed water is taken from the wastewater treatment plant. The reverse osmosis plant (C) is designed, for example, for a feed stream of 40-45 m ³ / h. Beforehand, the water is checked for suspended matter with a cloudiness measurement. If the turbidity is too high, close the valve and the Re cycle water is returned to depth filtration (A) (not shown). By simultaneously opening a valve, the reverse osmosis system is automatically switched to city water mode (StW). The turbidity measurement serves to protect the reverse osmosis modules from contamination.

Since the recycle water system can only guarantee an operating water volume of approx. 30 m ³ / h in continuous operation, a filtrate flow of approx. 10-15 m ³ / h is circulated during normal operation. The permeate stream is taken from the permeate collecting tank (PV).

Falls one above feed streams off, so automatically by means of the mechanical overflow valve Refreshed city water (StW). To the filtrate performance of the reverse osmosis system Alternatively, the circulated amount of filtrate can be boosted by city water be replaced.

To the Protection of the membranes of the reverse osmosis plant this was a fine filter upstream (not shown). The protective filter is by a Differential pressure measurement monitored. As soon as the differential pressure over the filter gets too big must be switched to the reserve filter by hand. Before the reverse osmosis modules Two emergency filters are installed. These secure the reverse osmosis Modules against a failure of the turbidity measurement. The RO modules consist of semipermeable membranes that predominantly passes only by water molecules can be. It becomes a retention rate the water content of about 95% achieved.

With the booster pump the application water is over the reverse osmosis modules which separates the sterilized water into permeate (filtrate) and concentrate. It will be a retention rate of Water content of about 85 to 98% achieved.

The quality the filtrate stream is monitored with a conductivity measurement. Reaches the conductivity not the required limits, so the permeate is not in the collection container put through, but completely recycled. Increases the conductivity of the filtrate continues to, then automatically flushing initialized to clean the membrane modules. The degree of pollution or The addition and the state of the modules will also be dealt with locally Monitored pressure measurements. Even with a deviating from normal operation differential pressure over the Membranes become a flushing process initiated.

the Feed stream of the reverse osmosis modules is preferably additionally a metering pump a hardness stabilizer dosed with the blocking of the membrane modules, e.g. prevented by calcium deposits shall be. The hardness stabilizer is in barrels held, the dosage is fully automatic.

The Permeate is moved into the permeate collection tanks (PV). The level in the collection container is controlled. If the permeate decrease is too low (high alarm) the RO plant is put into stand-by mode after previously the Rinsed membranes were. If the permeate is too high, the filtrate pump will be out of operation set (low alarm). Should of the reverse osmosis system (RO system) If no recycle water is removed, the high alarm closes the recycle water supply. In low alarm, the city water supply is opened. Furthermore, a rinsing sequence the reverse osmosis modules initiated. With the booster pump the recycle water is pumped to the reverse osmosis modules. there is volume controlled a hardness stabilizer added to the feed stream. In the case of a low alarm, the dosing pump is switched off.

With the filtrate pump, the filtrate is conveyed to the blending facilities of the cooling towers. Filtratüberschußmengen be stopped with the pressure maintenance and returned to the filtrate collection tank (PV). The filtrate collection tank (PV) is sufficiently large (about 100 m ³ ), so that failure and cleaning times of the recycle water system and the reverse osmosis system can be summarized. If the buffer time (2-3 h) is exceeded, the cooling towers can be operated for a short time without additional water. If necessary, city water can either be fed into the reverse osmosis system or directly to the cooling towers.

The Conversion of the additional water of the cooling towers to recycle water requires a conversion of the conditioning of the cooling water. A pure city water operation will therefore only take place if no demineralized over a longer period Water from the reverse osmosis system is available. The cooling tower conditioning must be adapted to the current conditions in this case.

The Concentrate emerging from the reverse osmosis is stored in the concentrate collection container (KV). The concentrate collection container (KV) is also with a level monitoring equipped. The concentrate stream is also with the concentrate pump to the Cementing equipment of cooling towers (KT) promoted.

Here a conductivity-controlled intersection with the filtrate flow takes place in order to set a minimum conductivity in the respective cooling water system. The intersection of the filtrate with concentrate is necessary in the cooling system and in The connected heat exchangers take place without excessive corrosion.

to Intersection of the filtrate will be max. 25% by weight of the concentrate needed. The remaining amount is over a pressure retention in the regeneration and Abschlämmwasser given.

commitment of filtrate / concentrate in cooling circuits The cooling water of all in the factory Cooling tower circuits is preferably with a hardness stabilizer and / or corrosion inhibitor, and optionally with a biocide conditioned. As a result, on the one hand prevents corrosion on steel and the others a precipitate of hardnesses suppressed. Furthermore, microbiological life will be minimized Deposits of biomass in heat exchangers and cooling water filtering pipes controlled. Next is an acid dosage in operation to higher To allow thickening.

Of the cooling tower is supplied with permeate by the reverse osmosis system. Becomes conductivity-dependent the filtrate to concentrate the minimum conductivity blended with concentrate. The hardness stabilizer and corrosion inhibitor is metered with the metering pump. The dosage takes place in dependence from the amount of feed water into a partial cooling water flow, the the pressure side of the cooling water circulation pump taken and through the dosing container in the original basin of the cooling tower is returned.

Of the Advantage of the above driving style lies in the greatly reduced consumption of corrosion inhibitor, almost no more consumption of hardness stabilizers, a greatly reduced consumption of biocides and the elimination of Acid dosage.

The The invention will be explained in detail with reference to FIG.

The pre-treated wastewater from the primary treatment is added to the filter (A) promoted. The wastewater goes through the filter horizontally and then removed from the side of the filter. Parallel is by means of an air driven mammoth pump (Aa) the Filter sand (down) constantly circulated from bottom to top. The filter sand (Ab) is cleaned in a washing device (Ac) and returned to the filter bed. It finds a classification of the filter sand instead, so that the to be filtered Wastewater flow through the filter bed in the direction of decreasing grain size. The continuous accumulating flushing water flow (Ac) from the sand purification is introduced into the chemical wastewater system (SW).

The Filtrate can be collected in an original basin or cache and stored intermediately. The pre-filtered wastewater is added to the UV system via a Pumped filter (F). In the UV system (B), the wastewater by means of UV radiation sterilized. A turbidity measurement decides whether the UV-treated water to the reverse osmosis (C) are supplied may require or re-filtration (A). The from the reverse osmosis plant (C) Leaving filtrate can be put into a buffer (PV) and then to the cooling towers (KT) are promoted. The salt concentrate (KV) is stored temporarily. If necessary, can the filtrate was blended with the concentrate before entering the cooling water systems become

Claims (11)

A process for the purification of industrial effluents, comprising the steps: (A) Filtration (B) UV irradiation and (C) Reverse osmosis, with the steps in the order A, B, C or A, C, B performed become. Method according to claim 1, characterized in that the filtration (A) with a Dynasand filter he follows. Method according to claim 2, characterized in that the waste water the filter horizontally goes through and discharged laterally on the filter becomes. Method according to claim 2 or 3, characterized in that the filter sand in the filter bed along the flow direction of the waste stream has different grain sizes and preferably the grain sizes in the flow direction lose weight. Method according to one the claims 2 to 4, characterized in that the filter sand constantly from circulated top to bottom is cleaned and optionally in a washing device and classified according to grain sizes and returned to the filter bed. Method according to one of the preceding claims, characterized in that in the filtration suspended solids and Particles in the range of 5 to 100 microns are removed to greater than 90 wt.%, preferably to a residual content of suspended matter of less than 5 mg / l. Method according to claim 1, characterized in that the UV irradiation with at least a preferably a plurality of downstream in the flow direction, mercury vapor low pressure radiators he follows. 8 method according to one of previous claims, being the ultraviolet irradiation takes place in two or more reactors connected in parallel. Method according to one of the preceding Claims, wherein step (A) is preceded by a chemical, biological and / or mechanical primary treatment (O), in particular the separation of water-insoluble impurities by means of flocculation aids, flotation aerators, oil separators, chemical neutralization, and / or activated sludge clarification. Method according to one of the preceding claims, wherein the purified by means of steps (A) to (C) and optionally (O) Water as recycle water in cooling towers or Process equipment is used. Method according to one of the preceding claims, wherein the purified by means of steps (A) to (C) and optionally (O) Water by blending with recovered from the reverse osmosis concentrate is adjusted to the required salt content, preferably for each cooling tower or each process plant separately. Having wastewater treatment device - one Dynasand filter, a UV system and subsequently a reverse osmosis system or - one Dynasand filter, a reverse osmosis system and subsequently a UV system, called each in the sequence of passage of the water to be purified, preferably with a primary treatment in front of the Dynasand filter.