Introduction: The DWWTP, employing activated sludge (A2O) technology treatment. The raw wastewater is drainage from wide range of communities and industrial streams waste from food industry. The designed treatment capacity of the DWWTP was 5000 cubic meters per day. The actual inflow capacity is approximate 5500 cubic meter per a day (~10 % increases).

Treatment process: Wastewater flows into an anaerobic pond follows to an anoxic pond. The wastewater enters into the bioreactor (Vb= 3200 cubic meters) for approximately 14 hours (HRT). Mixed liquor circulation is conducting between the bioreactor and the anoxic pound in order to induce pre-De-nitrification process.  The mixed liquor continues into the secondary clarifiers for phase separation.  Sludge circulation (RAS – returned activated sludge) persists from the clarifier back into the anoxic pond. Excess sludge (WAS-waste sludge) is removed from the process.

Secondary effluents quality history: Starting the year 2011, the treatment plant had produced high quality of effluents (COD- 23±11, BOD- 5±1, TSS- 10±2, and TN- 18±10, values presented in mg/L). Since 2012, the treatment plant had experience receiving an industrial new stream, resulting in a significant decreases of effluents quality (COD- 96±106, BOD- 28±45, TSS- 28±10, and TN- 35±18, values presented in mg/L). A year later (April 2013), BioCastle SBP technology was implemented within the WWTP bioreactor for helping to stabilize the treatment process and as well, in order to reduce the WAS fraction.

BioCastle treatment aims:

  1. Effluents quality increases for regulations compliance achievement.
  2. Excess sludge (WAS) reduction.
  3. Biological process stabilization.

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On bridge introdution devices installation

In this project, we had implemented 3 introduction devices on the bioreactor bridge. Each introduction device encases a perforated cage (60*60*30 cm in size) for SBP capsules hosting and implementation, at approximate 1 meter below water surface.
Left- DWWTP illustration that is presenting the SBP technology implementation sites by using SBP capsules introduction devices (Cranes) that are marks in red dots.
Middle- Illustration of on bridge introduction device (Crane attached to a perforated cage).
Right – Actual SBP capsules introduction devices. The attached perforated cages are placed above the water surface during a periodical operational activity.

 

Left - The perforated cages including the SBP capsules are inserted approximately 1m below water surface.
Right - Once a month the cages are pulling up out and gently washing them both inside (capsules) and outside (cage), in order to remove trapped sludge following by adding new SBP capsules. Picture of the SBP capsules within the perforated cage after two months of incubation and activity within domestic mixed liquor. After gently washing procedure, it can be seen that the capsules are clean from excessive bio-film and most of them are physically undamaged.

Finding:

  1. Secondary effluents quality improvement:
    Table 1: Summary of Secondary effluent quality data (Average ± SD)

    Parameter

    Previous treatment parameters (2012)

    During the SBP treatment

    parameters

    Public Health Regulations  – Effluent Quality for unrestricted Irrigation

    COD [mg/l]

    95±106

    23±8

    100

    BOD [mg/l]

    28±45

    6±0

    10

    TSS [mg/l]

    28±10

    10±2

    10

    Ptot [mg/l]

    5

    6

    5

    Ntot [mg/l]

    35±18

    17±5

    25

  2. WAS reduction: During the SBP treatment, we had noticed that in weeks, the bio-process was much more stabled and in consequences, secondary effluents quality was improved. Therefore, in order to reduce WAS amount, MLSS concentration was increased. This operational activity enabling us to achieve a significant WAS amount reduction, while keeping the biological process in a stable order.

Conclusions:

  1. The use of the SBP technology in a medium size domestic wastewater treatment plant that was suffered from effluents reduction quality and unstable biological process, was successful: All water chemical parameters (not including P) were significant improved. In addition the biological process stability was significant improved, as indicated by the SD values (Table 1).
  2. WAS amount reduction by approximate 20%, was achieved.
  3. SSV values were improved, indicating of better settlement activity.