nitrogen contents (TN): 32mg / L; total phosphorus contents (TP): 4.0mg / L;
ammonia nitrogen contents (NH3-N): 30mg / L. The designed effluent standards
can achieve to grade A standards ,which comes from "Municipal Wastewater
Treatment Plant’s Emission Standards of Pollutant " (GB18918-2002).Namely:
suspended solids (SS) ≤ 10mg / L; the oxygen demand for biochemistry in the 5
days(BOD5) ≤ 10mg / L; oxygen demand for chemistry (CODcr) ≤ 50mg / L;
total nitrogen contents (TN) ≤ 15mg / L; total phosphorus contents (TP) ≤
0.5mg / L; ammonia nitrogen contents (NH3-N) ≤ 5mg / L.
To achieve the effluent standards, the design uses A2/O-MBR Process to
treat the urban sewage water of shuanggou . Compared with conventional
activated sludge process, MBR process has the following characteristics on the
removal of organic carbon :Removal rate is high that can be generally greater
than 90% and the effluent water can reach the target of reuse water; sludge
loading (F / M) is low; hydraulic retention time (HRT) that required is short.
What’s more, it has high-volume load and strong –capability of shock load.
Membrane Biological Reactor replaces the traditional secondary separation of
solid with membrane in order to separate solid and liquid. As the film has high
retention rate and it can return the concentrated sludge back to the bioreactor so
that the bioreactor can have microorganism with high concentration and a long
sludge retention time. Compared with conventional activated sludge process the
MBR process can achieve better removal efficiency with shorter hydraulic
retention time. The concept of this design is replacing the secondary settling
tank in the traditional process with MBR membrane pool. On the basis of the
A2 / O biological sewage pool’s removal for nitrogen and phosphorus,
membrane pool has the further treatment function. To solve the problem that the
content of total phosphorus in effluent is not stable, we add specific
pharmaceutical to the intake department of membrane pool for removing
phosphorus.
The main structures of the treatment process include medium bar screen,
sewage pumping station, thin bar screen, Vortex-type grit chamber, A2 / O
biological pool, MBR membrane pool, Chlorine concentration tank, Storage
basins , sludge dehydration shop etc. In preliminary treatment, the original
water enters medium screening in order to remove heavy solids and floatable
materials, in case that it influences the working of the following devices and the
pipelines. Then it enters vortex-type grit chamber, which is used to remove
bigger inorganic sand of heavy density after the wastewater is pumped into the
thin screening. Afrer this the wastewater goes to the A2 / O biological pool for
organics, nitrogen and phosphorus removal .Then the wastewater goes to MBR
membrane pool for the remaining organic matter , nitrogen and phosphorus to
treat deeply. At last the wastewater enters Chlorine concentration tank and is
discharged.100% of sludge are recycled to the oxidation ditch and the rest are
pumped to sludge dehydration shop to discharge after thickening and
dehydration.