BCFS-Biological Phosphorus Removal New Technology

Abstract: BCFS process is in the Pasveer oxidation ditch (Pasveersloot) and the UCT process and based on the principle of the development of biological nutrient removal, new technology, which consists of five functional reactor is relatively specific composition, by controlling the reactor between the three cycles to optimize the reactor environment for the survival of bacteria, with a low sludge yield, nitrogen and phosphorus removal efficiency is high (all greater than 90%) and other characteristics, the effluent total nitrogen <5mg / L, is phosphate content of almost zero.

Keywords:: BCFS circulatory  nitrogen and phosphorus removal process
        1 BCFS Technology
        BCFS (Biologisch-Chemische-Fosfaat-Stikstof Verwijdering) process is by Mark Holland DELFT University of Technology Professor Pasveersloot and UCT processes and principles developed on the basis, which take full advantage of DPB (denitrifying phosphorus removing bacteria) and anoxic denitrification the role of phosphorus in order to achieve the complete removal of phosphorus and nitrogen removal of the best, for urban sewage treatment process without the need to add chemical agents. 
        Recently, the Netherlands BDG consulting firm has developed on this basis, a new reactor BCFS. The reaction is controlled by five coaxial ring composition, in turn constitutes a function of the relative specificity of the five separate reactor. These coaxial with the piston ring so that water flow and completely mixed flow of the advantages of using pre-cast concrete construction of such an integrated structure to reduce the engineering investment, while making simple layout of wastewater treatment plant, saving the project investment and construction projects. 
        1.1 Process
        BCFS process will be different functions of each type of bacteria in a space separated, and through the circulatory system to control the different growth environment. 
        BCFS process shown in Figure 1. 
        Figure 1 shows that by, BCFS process by the five functional independence of a relatively specific reactor (anaerobic tank, select the pool, oxygen tank, anoxic / aerobic pool, aerobic pool) and 3-way circulatory system composition, the cycle The impact, such as shown in Table 1.






Cyclic code

A major role in

Control Point

Control of oxidation-reduction potential (mV)


A

Provide sludge phosphorus release condition (ie, nitrate-N <0.1mg / L)

Anaerobic Pond

-450 ~ -300


B

Provide nitration mixture

Anoxic tank

-150 ~ 0


C

Denitrification

Anoxic / aerobic pond

-100 ~ 50 (or 0)
        1.2 Features
        The main features of BCFS process can be summarized as follows: 
        ① The nitrogen and phosphorus removal rate high, can the effluent total nitrogen <5mg / L, phosphate levels are almost zero.
        ② SVI value is low (80 ~ 120mL / g) and stability (in summer 80mL / g, in winter 100mL / g, max 120m L / g), which can effectively reduce the aeration tank and secondary sedimentation tank volume.
        ③ simple control, through the oxidation-reduction potential and dissolved oxygen to be effective in the implementation process stability, especially beneficial for load control. 
        ④ Compared with conventional wastewater treatment plant, the sludge production by 10%, thereby further reducing sludge disposal costs. 
        ⑤ the use of DPB of biological phosphorus removal (measurement results show that about 50% of the phosphorus removal by DPB), so that carbon (COD) can be effectively used, so that the process is COD / (NP) value of relatively low circumstances remain in good working condition, while phosphorus chemical dosage required for greatly reduced. 
        ⑥ devices using biological phosphorus removal sludge was rich in phosphorus, so that recycling of phosphorus is possible. 
        ⑦ with Pasveer the same load of sludge oxidation ditch. 
        2 Functional Analysis
        2.1 Comparison with the oxidation ditch process
        Pasveer oxidation ditch with secondary sedimentation tank, the system's SVI value is usually 100mL / g, sludge concentration 4kg/m3. Accordance with the needs of each population equivalent volume of 0.25m3 of the oxidation ditch, Pasveer oxidation ditch sludge nitrogen load of 0.01g / (kgMLSS * d) (which is calculated on the basis BCFS process); if the treatment process has the primary settling tank, then the sludge loading obtained 0.015 kg / (kgMLSS * d). 
        Sedimentation tank in the Netherlands has two common oxidation ditch, the SVI value of winter is about 150mL / g, maximum sludge concentration 4kg/m3, while the BCFS process SVI value 120mL / g (VI value decreased mean sludge concentration increased, that is, 5kg/m3), so that the total volume of BCFS process than the average 20% reduction in oxidation ditch. 
        General oxidation communicated plus chemical phosphorus removal, which makes the sludge at least 10% of the chemicals, can be seen in comparison with ordinary oxidation ditch, BCFS the total volume of the reactor oxidation ditch is only about 70% of volume. 
        In addition, BCFS phosphorus removal process with the aeration tank separation of biological sludge from the chemical agent contamination is conducive to the use of phosphorus-rich sludge. BCFS process requirements of the secondary sedimentation tank depth of less reserved for the high concentration of sludge sufficient space. 
        2.2 Functional Analysis of the constituent units
         ① anaerobic tank
        Anaerobic conditions, anaerobic pond water and from the anoxic tank through the return of oxygen mixture (where NO3-N <0.1mg / L, namely the control of nitrate into the anaerobic tank nitrogen concentration is low enough) to maintain, so Sewage in the volatile fatty acids (VFA) will only be used for biological phosphorus removal. 
        Return aerobic MLSS concentration and some of the same, so the concentration of anaerobic sludge pool is the ultimate concentration of 1 / 2 ~ 3 / 4, namely, 2.5 ~ 4kg/m3.
        BCFS the anaerobic part of the process and traditions of the selectors with the same sludge load, the difference is that the former is strictly anaerobic, and all of the volatile fatty acids in water have been used in biological phosphorus removal. BCFS process the number of phosphorus removal bacteria more than the conventional process, can withstand a greater load peak, for example, the peak load when it rains is the usual two-fold, while the BOD load only the usual 1 / 2, BCFS phosphorus removal process peak BOD bacteria can be stored, when the BOD is insufficient immediate release. Found in practical engineering, regardless of whether it rains, use of BCFS process effluent total phosphorus concentration is almost the same, this is because the process will be the peak BOD and phosphorus removal bacteria on the storage, the follow-up treatment process and setting the effective control of STP (phosphorus removal device) combination of three methods to realize the excess of phosphorus removal: 
        a. Separation of phosphorus in the anaerobic tank and the primary settling tank sludge inorganic precipitation; 
        b. from the secondary settling tank sludge phosphorus released from the formation of phosphate compounds; 
        c. by dosing FeCl3, the pool of acid digestion to remove again. 
        This combination makes the smallest amount of chemicals, the effluent phosphate content of Chiang Kai-shek to zero. Sludge removal of phosphate occurred in the sludge process, which indicates that the biological sludge sludge process could be pollution from chemicals, so that the activity of microbial BCFS system from the impact of chemical sludge. 
        In order to improve nitrogen removal, BCFS process design for a long sludge age (usually 50d), which cause trouble to the phosphorus. BCFS chemical method to remove the biological removal of phosphate is not, which is due to end in the anaerobic pond effluent phosphate content, and therefore in the anaerobic tank set up a back-end device for chemical phosphorus removal and phosphorus removal. Different from general-line phosphorus, the phosphorus sludge pump device is sent to the sludge thickening tank, after adding FeCl3 chemical phosphorus removal, the treated sewage sludge will no longer return to the structure, thus removing the accession to the Chemical phosphorus removal agent after the sludge activity. Because the anaerobic pond anaerobic conditions, in some cases (such as the long rains, etc.) may be damaged under the influence bacteria release phosphorus release phosphorus and PHB synthesis caused by deterioration of water quality, then pass legislation to increase phosphorus removal the flow device to enhance the water quality. This process can be located at the outlet of the line monitor to achieve phosphate control is very simple and can stable operation. 
        Settings in the anaerobic phosphorus pool back-end, in order to get a relatively stable hydraulic conditions, the process will be anaerobic tank and set up two split tailgate, the two formed between baffle a similar sedimentation tanks of the hydraulic flow field is conducive to mud and water separation. 
        ② Select pool (device) 
        Selector for preventing sludge bulking is necessary. The oxygen concentration in the selector is zero, return sludge in secondary sedimentation tank of trace nitrate can be quickly removed. In this environment, the filamentous bacteria grow very slowly, returning in sewage sludge can be adsorbed almost all of the remaining COD (only 10min, so selectors can be relatively smaller), by selecting the device in the water after the effluent COD concentrations and system COD concentration was almost equal. Denitrifying phosphorus removing bacteria in the selection pool, also play a role in this process is the continuation of the process of anoxic reaction tank. 
         ③ anoxic tank
        Anoxic tank has two functions: first, to get the non-nitrate denitrification of sludge and thus improve the efficiency of anaerobic phosphorus release the pool, followed by the use of the pool of nitrate to the aerobic phosphorus removal.
        Anoxic denitrifying phosphorus removal in the Holten sewage treatment plants found in the industrial trials, and further theoretical studies have shown that bio-sludge in the STP containing 1 / 2 or more phosphorus removing bacteria, phosphorus removing bacteria in these there is a / 2 These are the denitrifying phosphorus removing bacteria, namely the use of denitrifying bacteria to achieve the real purpose of the biological phosphorus removal, but also reduce the need for carbon source and higher demands. 
        ④ anoxic / aerobic pond 
        Anoxic / aerobic pond main function is nitrogen, under normal circumstances the pool may from time to oxygenation, hypoxic conditions, through a mixture of aerobic tank to maintain reflux. Compared with the usual oxidation ditch, the pool is in continuous hypoxia, which means that simultaneous nitrification and denitrification have been, but not the amount of oxygen constraints. BCFS process will anoxic / aerobic pool, aerobic pool allows each part of the separation of the removal rate reaches the maximum, its main advantages are: 
        a. In the anti-nitrification and phosphorus removal does not affect the case of the sludge can achieve the maximum rate of mineralization; 
        b. help control the SVI value; 
        c. to maximize the use of denitrifying phosphorus removing bacteria to make the minimum sludge production; 
        d. adequate oxygenation can load stability at the lowest value; 
        e. oxidation-reduction potential and dissolved oxygen through the realization of automatic control. 
        Aerobic pond  ⑤
        With the conventional treatment process, its main function is to remove COD, BOD and ammonia nitrification.  reposted elsewhere in the paper for free download http://eng.hi138.com
    3 application prospects
        BCFS the application of technology in the Netherlands there are 10 cases currently planning to address the scale of 10 * 104m3 / d sewage treatment plant in Rotterdam. 
        Table 2 for 3 with BCFS process municipal wastewater treatment plant design and operation.




Item

  

Holton

Genemuiden

Dalfsen


Design parameters

BOD load [gBOD / (population equivalent d)]

54

40

35


Anaerobic pond volume (m3)

350

850

900


Select pool volume (m3)

90

  

400


Anoxic tank volume (m3)

700

  

2200


Anoxic / aerobic tank volume (m3)

790

3750

  


Aerobic tank volume (m3)

1580

3750

4500


Total volume (m3)

3500

8350

8000


Back to the flow rate (m3 / d)

4400

5200

4200


Operating parameters

Sludge loading [gCOD / (kgSS * d)]

134

125

72


Sludge production [gSS / (population equivalent d)

29

32

30


Me / P (mol / mol)

0.82

  

0.3


SVI (mL / g)

99 ± 16

94 ± 14

118 ± 14


Removal rate (%)

94.2

91.0

93.0


COD

97.8

97.7

98.9


BOD

92.7

91.9

90.4


TN

94.9

93.5

92.4


TP

  

  

  


Note: Me / P refers to the synergy of the cation and phosphorus and phosphorus stoichiometry number.
        Holton sewage treatment plant originally two sets of parallel to the intermittent aeration activated sludge tank composed of transformed BCFS after adding a new reactor, and the original and part anaerobic aeration tank is divided into two parts oxygen, while increased anaerobic reactor volume (total volume of about 10%). Mark Professor (1997) in its original running processes on the basis of research to transform the sewage treatment plant of nitrogen and phosphorus removal is more stable, less the value of its SVI of sludge and stable and does not require dosing FeCl3 (ie, no external chemicals). 
        In our increasingly strict environmental protection requirements, the standard case of higher and higher, especially in the control areas, such as phosphorus and the Dianchi Lake, Taihu Lake Basin using BCFS application process there will be a great prospect, mainly: 
        ① good treatment effect of the process, the effluent water quality (total nitrogen <5mg / L, phosphate concentration is close to zero), which can effectively reduce the eutrophication caused by nutrients (nitrogen, phosphorus) emissions;
        ② As the process without primary sedimentation tank, the treatment effect in the same process under the BCFS investment minimum, low running costs; 
        ③ As a result of coaxial circular structure of pool-type, which can effectively save area; 
        ④ can realize automatic control, and the simple, lower investment, overcoming the previous introduction of foreign technology, at the same time need to spend a lot of foreign exchange to purchase their equipment, a large number of the drawbacks of self-control;
        ⑤ process layout simple and beautiful. 
        In addition, industrial production has been from the Netherlands to see the sewage plant, BCFS process for the transformation of the existing oxidation ditch process and have a good adaptability. 
          Subject to a city sewage treatment plant commissioned, the author and the Netherlands experts, based on the characteristics of China's urban sewage and the existing emission standards for the design, the result as shown in Table 3. Can be seen, using BCFS process reactor volume than the existing A2 / O process large, but smaller than the oxidation ditch process. 




Item

Value


Design size (104m3 / d)

30


Design of Water Quality

COD (mg / L)

350/100


BOD (mg / L)

200/20


Ammonia nitrogen (mg / L)

45/20


TP (mg / L)

5/0.5


  

Total volume (m3)

18000


BCFS Pool

Anaerobic tank (m3)

2160


  

Select pool (m3)

1440


  

Anoxic tank (m3)

  


  

Anoxic / aerobic pond (m3)

  


  

Aerobic pond (m3)

  


Note: ① design of water quality in bar '/' means 'water / water'; ② the water column ammonia 20mg / L for total nitrogen concentration, using the 'Taihu Lake, Jiangsu Province, total phosphorus, total nitrogen discharge standards' (DB32 / 191-1998) in a standard; ③ water PO43 - P concentrations of <0.1mg / L; ④ BCFS pool using coaxial circular structure.
        
          References:
        [1] van Loosdrecht MCM, Brandse FA, de Vries A C. Upgrading of waste w ater treatment processes for integrated nutrient removal-the BCFS process [J]. Water Sci Tcehn, 1998,38 (3) :12-23.
        [2] van Loosdrecht MCM, Kuba T, van Veldhuizen HM, et al.Environme ntal impacts of nutrient removal rocesses: case study [J]. J of Environ Eng, 1997, 38 (1) :33-40.
        [3] Kuba T, van Loosdrecht MCM, Brandse FA, et al.Occurrence of de nitrifying phosphorus removing acteria in modified UCT-type wastewater treatme nt plants [J]. Wat Res, 1996,31 (4) :777-786.
        [4] Xiaodi Hao, van Loosdrecht MCM, Sebastiaan CF Meijer, et al.Mo del-based evaluation of enitrifying removal in a two-sludge system [J]. J of Environ Eng, 2001,42 (2) :112-118 .
        [5] Jin-Song Guo, Huang Tien-Yin, Teng-rui. Biological nutrient removal processes in the micro-organisms and their relationship [J]. Pollution control technology and equipment, 2000,1 (1) :8-15.
        [6] Shen Yao-liang. Wastewater biological nutrient removal process design and operation of several issues to be considered [J]. Environmental Science and Technology, 1996, (2) :36-40. Reposted elsewhere in the paper for free download http: / / eng.hi138.com

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