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Quite often the existing waste water treatment technologies are not able to ensure adequate sewage treatment especially due to high concentration of saturated pollutants or specific pollutants. To solve the following problems, are carried out research and developed new technologies to help ensure the quality of the waste water treatment, regardless of the specific circumstances.

Membrane bioreactors

Membrane bioreactors (MBR) are the devices that combine a membrane filtration technology and biologically active sludge treatment processes, which are widely used in industrial and municipal waste water treatment.

MBR technology has become economically available for municipal waste water treatment in cases where there is a need for deeper treatment, as well as when you need to improve or renew existing treatment equipment.

Compared with the traditional purification technologies, MBR system ensures a complete disinfection of purified water and achieve better separation of contamination (causing water recycling possibilities), and takes up significantly less space.

The MBR is the biological waste water treatment equipment where activate sludge reactor is combined with a membrane filtration process, which in turn performs the clarification and disinfectant functions of purified water.

A dual configuration the MBR is the most commonly used for waste water treatment. In one case, the separation process is carried out in separately placed filtering module, but in another configuration, filtration module is immersed in the bioreactor.

Shared configuration

The clarified waste water is entered in the bioreactor, where is made oxidation of organic and inorganic impurity. Liquid mixture with suspended solids content of 10-20 g/l are transported from the bioreactor and pumped through the cross flow membrane filtration module. Membranes filtrate composes and outflow of purified water, while the densified remainder is returned into the reactor. Excess biomass is transported to utilization.

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Submersible membrane modules

In these modules can be used the cored fibers microfiltration and ultrafiltration membranes. Fibers are collected in the bundles and integrated into cassettes from which, in turn, form the modules. Module cassettes for removal of the filtrate, are connected to the pipeline system and immersed in the bioreactor. In the later configuration, in order to make easier the cleaning process, cassettes are immersed in a separate tank. The filtrate pumps cause the rarity, which draw the fluid into the hollow membrane, but suspended substances remain in the reactor. In this way, you reach water clarification and do not require the pumps for returning of mud.

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Previously viewed most often used MBR systems. Innovative systems have the following characteristics:

  • purified water is high quality and does not contain the bacteria;
  • high organic loads (2-4 kg COD/m3 per day);
  • high index volume of sludge (10-20 g/l);
  • high sludge age (30-100 days);
  • about 35-45% less excessed sludge;
  • contribute the development of slow-growing bacteria etc.

Cost comparison

The investment costs - in MBR systems are achieved a compromise between the construction costs and the cost of mechanical and electrical equipment, which consists primarily of the membrane and of the complicated process control costs. Average investment costs can be relatively lower than traditional systems, which are complemented with deeper treatment facilities.

Operating costs-MBR system operating costs quite often are larger comparing to the traditional equipment, which is formed due to higher energy consumption because the system staff and sludge management costs are similar, at the same time, the MBR systems characterized by smaller quantities of produced sludge.

In the comparable circumstances, in the investment score the MBR equipment have ability to compete with the traditional biological treatment devices. On the other hand, the lack of MBR system as relatively high energy costs becomes insignificant, as in the case when the traditional technology is enhanced with tertiary treatment and disinfection in order to achieve the MBR System equivalent treatment level.

However, it should be noted that the large flow and weak concentrated waste water treatment, such as municipal waste waters, MBR system can't financially compete with traditional activate sludge systems if occurs all the following conditions:

  • the populated place municipality has a lot of free space for the construction of the WTE
  • there are no high quality requirements to the purified water, including nutrients and/or heavy metals removal
  • no reuse or recycle of treated water 
  • restoring an existing WTE is not intended increase of efficiency of equipment productivity or purification grade
  • in the case where one or more of the above conditions are not applicable, it is necessary to value the economic validity of the MBR system

Whereas in the case of small amount of concentrated water treatment, for example, the washed water from waste landfills, MBR system has a significant advantage over traditional WTE in the exhaust quality and in the case of costs.

MBR equipment can be fully industrially set and transported to the installation place as assembled or disassembled. In the installation place, the equipment will be built in in the previously prepared concrete or steel tank. The supplied equipment is delivered assembled with the entire electrical and mechanical bandage, therefore is reduced the required setup work, and the equipment are easily transportable. The construction of the equipment depends on the inflow and exhaust, climate and other factors. The purified in the equipment water, can be reused for watering the garden, park, as well as pot rinse.

ANAMMOX®

ANAMMOX is an abbreviation for ANaerobic AMMonium OXidation, or anaerobic ammonium oxidation, and it calls the global importance of microbiological processes in the cycle of nitrogen. Mediation of bacteria in this process was set in about 20 years ago and at that time it was a big surprise to the scientific community.  

ANAMMOX ® process is a new biological process, providing new opportunities to discharge nitrogen from wastewater. In this process involved bacteria causing a shorter path for the nitrogen movement cycle and ensures nitrite oxidation by free nitrogen using nitrite electron as an acceptor. The process is sustainable and very financially effective as feature of retention ammonium. In comparison with traditional nitrification/denitrification (separated the returned water treatment process in which following a nitrification of ammonium at intensive aeration and increased temperature, as well as the reduction of nitrate to free nitrogen, with help of the denitrificating bacteria and assimilated carbon injection), the operational costs are reduced by up to 90%, CO2 emissions are reduced by up to 90%. In addition, the device takes half less space than the traditional nitrogen extraction equipment.

ANAMMOX ® process takes place is a two-stage reactor and nitrogen removal from the water of dewatered sludge, and other waters with a high content of ammonia. The process combines two technologies that have been developed independently. SHARON (Single reactor for High activity Ammonia Removal Over Nitrite) process provides a partial oxidation of ammonia and nitrates (nitrification), while in the following ANAMMOX process takes place the anaerobic ammonium oxidation through free nitrogen.

ANAMMOX ® process takes place in two stages: 

  • in the first stage - in the SHARON process take place partial oxidation of ammonia to nitrites. The process occurs in the same reactor, in which is continuous agitation, relatively high temperature (35°C) and is not carried out retention of biomass
  • in the second stage take place the ANAMMOX process. In this process takes place anaerobic oxidation of ammonium until free nitrogen which is ensured by anammox bacteria, which are used by nitrite as electron acceptor

ANAMMOX ® technology allows you to purify high concentrated waste water, including fermented sludge dewatering waters, in the individual reactor with high performance before the water return in the common purification process. By this can be substantially reduced the total nitrogen load (up to 25-30%) of treatment devices in and improved nitrogen content indicators in the outflow of the equipment.

In comparison with traditional purification of return water -nitrification/denitrification, operating costs of ANAMMOX® process are reduced by up to 90% for up to 60% reduction in energy consumption and CO2 emissions are reduced by up to 90%. In addition, ANAMMOX® process technology takes on up to 50% less space and produces significantly less excess sludge.

ANAMMOX ® process can be applied to reduce ammonium from the waters of different origins, with relatively high concentrations of ammonium (NH4+-N >100 mg/l). Technology is applied on treatment devices of municipal wastewaters, for treatment of water obtained from fermented sludge dewatering, as well as treatment of various industrial waste waters.

ANAMMOX® reactor scheme

Reactor combines the high throughput capacity, efficient retention of biomass and most anaerobic wastewater treatment properties. Purified water (after SHARON process) is entered in the bottom compartment of the reactor, where it is mixed with recirculating water and recirculating gas from the upper section. The first section contains an anaerobic granular sludge, where is carried out most of conversion of the ammonia and nitrite into nitrogen gas. Deployed three phase separators at the top of the section (liquid-gas-solids) receive the produced gas and further conducts it for operation of gas lift (airlift). The liquid is moved from the lower bin to the less mixed upper compartment, which layers and serves mainly for retention of biomass and addition improvement of outflow quality. Supply of purified water from the bottom of the reactor and its mixing with recircylating exhaust water is made to ensure adequate upward flow rate and reduce stress on the formation process of granules.

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Biomembrane technologies

Biomembrane is a set of micro-organisms, where cells are sticked one to another and/or any surface. These attachments take place due to squeezing into polymeric substance of outside cell made by itself – for example, in polymer or polysaccharide, so quite often biomembrane reminds the slime. Biomembrane can be formed on the natural or artificial surfaces and it is the dominant form of life of the micro-organisms, in the natural, industrial and hospital environment.

Biomembrane is also widely used for treatment of wastewater. For this purpose, there is located the artificial, moving or fixed, synthetic material filling in the treatment devices, which is characterized by a small weight and a relatively large surface area.

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When such additional elements contacts with waste water and biologically active sludge, the bacteria attaches to its surface and start to proliferate to gradually establish a thick layer of biomembrane. In the biomembrane existing bacteria continue to rip off organic and inorganic compounds in existing waste water, thereby making its purification.

Comparing with the traditional activated sludge equipment, biomembrane technology has several advantages: 

  • biologically active material is placed in a fixed manner in the device, therefore it is no need for its recirculation from  secondary settling tanks
  • fixation of biomembrane allows you to achieve high content of biomass in the reactor, as a result it is possible to clean up highly polluted waste and reduce the capacity of the bioreactor
  • the hydraulic stability of the process – biomembrane technology is robust against the flow rate fluctuations and biomass are not flushed out from the device due to a temporary increase of the flow
  • chemical stability of the process – thanks to the layers of biomembrane that form on the surface of additional elements, a temporary entering in the reactor of toxic substances (e.g. disinfectants) usually does not destroy the entire biomass and it recovers much faster than in case of suspended active sludge
  • intensive nitrification – thanks to development of fixed nitrification bacteria, biomembrane systems ensures intensive nitrification even at little sludge age
Below described some sewage treatment technologies that are available in the market, in which are used biomembrane processes.

Moving Bed Bio Reactor (MBBR)

MBBR system is made for sewage treatment process, based on the biomembrane processes and ensures organic carbon and nutrient retention, without recirculation of active sludge. The process is simple, durable, and requires minimal intervention of the operator. Sewerage is treated in one or more step systems, which are filled with the free floating additional elements which are covered with biomembrane. MBBR systems are conformable for a wide range of application: starting with the pre-treatment of industrial waste water and ending with the total municipal waste water treatment system - as individual or to complement the existing system.

MBBR reactors designed to purify the clarified waste water, so previously need then to be settled. The reactor is filled with free floating, covered with biopmembrane filling elements. Suspended condition is held by constant aeration from the bottom of the reactor, which at the same time ensures oxygen which is necessary for bacteria.

Filling elements from leaching are protected by separation elements or sieve which are placed in reactor outflow. In turn detached or mortified biomass form the filling element is removed along with the treated water. For this reason, after the treatment in the MBBR reactor requires water clarification using settling, filtration or flotation.

In order to ensure the necessary level of wastewater treatment, or to provide additional nutrients distribution, you might need to set up supplementary MBBR reactor, in which is maintained anauxide conditions, f.e., in the case of nitrogen retention.

Integrated Fixed Film Activated Sludge (IFAS)

This system, similar to MBBR, for wastewater treatment is applying the filling elements and biomembrane technology, but additionally in the bioreactor are recirculating and maintained also suspended biological active sludge. The following biological material coexistence ensures development of specific nitrificating biomembrane on the filling elements, acting simultaneously with the activated sludge which depleting organic carbon. This system is specially applicable for the existing treatment system restoration with the aim of increasing removal of nitrogen and BOD without further construction og reservoir. The system can also be used to build a new devices.

In IFAS bioreacotrs waste water are entered after the mechanical pre-treatment. Bioreactor is usually divided into several stages of the process that pass in aerobic and anaerobic anoxic partition. Filling elements with biomembrane are placed in the aerobic stage the special exhaust grooves hold them form leaching. The process is based on biological active sludge microorganism and biomembrane organisms fight for nutrients. The suspended biomass has the absolute advantage of BSP assimilation, so in the biomembrane evolving mainly nitrificating bacteria. As the result in one reservoir are located two different populations of microorganisms that fulfil totally different functions, thereby significantly increasing the potential for treatment at constant volume.

Waste water after treatment in the bioreactor are clarified in the secondary settler and released from the system, while the separated sludge mud and biomembrane particles are returned to the purification process and entered in the reactor's inlet bin, thereby maintaining the desired in the reactor suspended biological active sludge quantity.

Fixed Film Activated Sludge Treatment (FFAST)

In this system, as in the described above system, are combined MBBR and active sludge technologies. In the FFAST technology sewage water at first are cleaned with MBBR reactor with further processing of traditional activated sludge process. In such combination is used the capacity of MBBR reactor, at the relatively small volume of the reactor to provide significant reductions in BOD, as well as following ability of the active sludge to provide high-quality outflow.
FFAST process is the optimal for use of treatment plants with a limited area in which needs to ensure consistently high outflow quality simultaneously with the resistance to the peak loads. The system is suitable for use both in the construction of new equipment and development of high pressure equipment.

The clarified effluent are entered in rough, aerating one-step filter, where are placed filling element, covered with biomembrane. Purification reduces in the filter dissolved content of BOD in the effluent  about 45-70%. Therefore the following biological aerobic activated sludge system cleans up only a small part of the organic load and it can be considerably in comparison with traditional equipment. As a result active sludge system performs only a after purification thus providing a high quality of the exhaust. After biological treatment following clarification of water in secondary mixer, discharge of the clarified water and recirculation of the sludge. In addition, you can perform a partial recirculation of sludge into MBBR reactor, thus achieving control effect of the development of filamentous organisms.

In addition the advantage of FFAS system is the ability to handle peak loads, as well as a certain number of toxic substances and thereby protect the following suspended activated sludge processes. Thanks to the layers of biomembrane after influence of toxic substances it has ability to recover much faster than an equivalent quantity of the suspended biomass.

Roughing Filter for Biological Nutrient Removal (RF-BNR)

The system offers a cleaning process that is based on the biomembrane to ensure the following removal of organic carbon after nitrification and denitrification without sludge recirculation. Denitrification takes place in both - in the preceding denitrification reactor and innovative, fixed/movable-bed reactor with intensive endogenous denitrification. RF-BNR system is extremely well adopted for use in small and medium-sized municipalities, in cases when there is a deep need for removal of nitrogen and minimal involvement of the operator.

BioKube

The BioKube is Danish company’s biological wastewater treatment system which is provided for small – 5-50 HE (human equivalent) as well for large 100-5000 HE objects  for treatment of wastewater, supposing that 1 HE generates 150l per day and night of wastewater. The distinction of the device is that it can be settled with additional equipment for chemical desorbs of phosphorus.

Devices work based on biomembrane technology – basic purification goes on when water flow through submerged aerated biomembrane filter blocks.  Purification of wastewater begins in the septic first clarification tank (septic tank), where by using company’s patented process, in additional to clarification of the water, there is performed reduction of the Hydrogen Sulphide. Purified wastewater with exact intervals is pumped into the BioKube first tank, where water flow through biofilter block and comes pulldown of organic material. Further wastewater flow through purifying partition where settles separated biomass. After purifying, water flows to second section where process repeats. In the third section of the device comes nitrification and desorbs the ammonium/ammonia nitrogen, after which water is purified and outputted for the device. Clarified water can be discharged into environment or reused – for watering etc. purposes.

The sludge, which settles in each section, is pumped back to the pre-settling tank (septic tank), where stored and emptied one – two times per year. If necessary, BioKube units can be settled with additional equipment for a phosphorus precipitation. Phosphorus is removed by adding an Aluminum chloride to the sludge, which is pumped from treatment unit sections and pre-settling tank (septic tank). Thereby phosphorus precipitates a non-dissolvable salt.

Small (5-30 HE) BioKube equipment available in 3 standart modification:

  • BioKube Pluto – for one house, ensure outflow result BSP5 < 25 mg/l, COD
  • BioKube Venus – for one house, ensure outflow result BSP5 < 10 mg/l, COD
  • BioKube Mars – 10-30 HE, ensure outflow result BSP5 < 10 mg/l, COD

Lielo (100-500 CE) BioKube sistēmu darbības pamatā ir tie paši attīrīšanas procesi, kā mazajām iekārtām. Lielās iekārtas pieejamas ar ražību 50, 100, 200, 300, vai 500 CE, kuras tiek piegādātas un uzstādītas pilnībā komplektētu moduļu veidā.

Priekšrocības:

Iekārtu galvenās priekšrocības izriet no bioplēves tehnoloģiju priekšrocībām

  • bioloģiski aktīvai materiāls iekārtā atrodas fiksētā veidā tādēļ nav nepieciešama tā recirkulācija no otrējās nostādināšanas rezervuāra
  • procesa hidrauliskā stabilitāte – bioplēves tehnoloģija ir noturīgāka pret plūsmas ātruma svārstībām un biomasa netiek izskalota no iekārtas dēļ īslaicīgas plūsmas palielināšanās
  • procesa ķīmiskā stabilitāte – pateicoties bioplēves slāņiem, kas veidojas uz pildelemenu virsmas, īslaicīga toksisku vielu nokļūšana reaktorā (piem., dezinfekcijas līdzekļi) parasti neiznīcina visu biomasu un tā atjaunojas ievērojami ātrāk kā suspendēto aktīvo dūņu gadījumā
  • tāpat par priekšrocību uzskatāma iespēja veikt padziļinātu, ķīmisku fosfora izdalīšanu. Savukārt dozēta, vienmērīga notekūdeņu padošana iekārtā no septiķa izlīdzina diennakts plūsmas nevienmērības, mazina biomasas stresu dienās kad cilvēki dodas brīvdienās un tādejādi nodrošina stabilāku iekārtas darbību

Trūkumi:

Kā relatīvu mazo attīrīšanas iekārtu trūkumu jāmin, ka BioKube iekārtās attīrāmi tikai iepriekš dzidrināti sadzīves notekūdeņi. Tātad papildus BioKube iekārtai, jāuzstāda vēl viena iekārta – septiķis.

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