1, processing flow:
↓ air ↓ disinfectant
Raw water → regulating tank → pretreatment → membrane bioreactor → disinfection → reclaimed water.
Sludge
2, design selection points:
1) The reclaimed water treatment process consists of various sewage treatment units, and usually includes three parts:
(1) Pretreatment: grid and regulating tank.
(2) Main treatment: flocculation and sedimentation or air flotation, biological treatment, membrane separation, land treatment, etc.
(3) Post-treatment: filtration (sand, activated carbon), disinfection, etc.
Among them, pre-treatment and post-treatment are generally basically the same in the above processes. The main treatment process should be selected according to different requirements.
2) When adopting membrane treatment process (membrane separation, membrane bioreactor, etc.). ), reliable pretreatment process units and membrane cleaning facilities should be designed to ensure the long-term stable operation of the membrane system.
3) The new technological process must be tested by experiment or practice, and the corresponding evaluation, appraisal and acceptance opinions can be put forward, as well as the treatment effect, efficiency and water quality inspection report data of the process.
4) When the wastewater containing excrement is used as the reclaimed water source, in order to prevent more solid suspended solids from blocking the raw water collection pipeline or bringing it into the reclaimed water treatment system, the raw water needs to be pretreated by septic tank.
5) When reclaimed water is used for waterscape, heating, air conditioning, cooling water and other purposes, if the adopted treatment process can not meet the corresponding water quality standards, advanced treatment facilities, such as activated carbon, ozone, ultrafiltration or ion exchange treatment, should be added.
6) Precipitated sludge, activated sludge and chemical sludge produced by reclaimed water treatment should be properly treated. When the amount of sludge is small, it can be discharged to septic tank for treatment. For the reclaimed water treatment station with large sludge, mechanical dewatering device or other methods can be used for treatment.
Membrane bioreactor is a new and efficient sewage treatment technology which combines membrane separation and biological treatment. The denitrification mechanism of industrial nitrogen-containing wastewater includes two basic processes: nitrification and denitrification. Nitrification refers to the process of transforming ammonia nitrogen into nitrate nitrogen, which is mainly completed by two aerobic autotrophic bacteria, nitrosobacteria and nitrifying bacteria. [ 1]
Toray mbr membrane technology firstly removes biodegradable organic pollutants from water through activated sludge, and then forcibly intercepts activated sludge and most suspended substances in the bioreactor by membrane modules, thus realizing solid-liquid separation of purified water and activated sludge, thus strengthening biochemical reaction and improving sewage treatment effect and effluent quality.
The MBR treatment process has obvious treatment effect on COD in wastewater from nitrogen fertilizer industry, and its biochemical strain has a short acclimation period, showing a stable effect from the third day. In the stable treatment stage and normal operation stage, a high COD removal rate can be maintained, and the removal rate is basically above 90%. The average outlet COD is controlled below 30mg/L.
Characteristics of MBR treatment process
1) has high treatment efficiency, and the effluent can be directly reused. Because the hollow fiber membrane has an efficient separation effect on the mixed liquor of the biochemical reactor, the sludge can be completely separated from the effluent, and the SS and turbidity of the effluent can be close to zero. At the same time, because the loss of activated sludge is almost zero, the concentration of activated sludge in the biochemical reactor is about 2~6 times higher than that in the traditional process, which greatly improves the nitrogen removal ability.
2) The system has stable operation, simple process, less equipment and small floor space. Due to the high concentration of activated sludge in MBR technology, the volume load of equipment is large; Strong resistance to water inflow fluctuation and impact, and stable operation. This process can not only greatly reduce the volume of biochemical reactor-aeration tank, but also miniaturize the equipment and structures, and even omit the primary sedimentation tank and the secondary sedimentation tank, thus reducing the system area.
3) Long sludge age and little excess sludge. When the sludge concentration is high and the influent load is low, the ratio of nutrients to microorganisms (F/M) in the system is low, and the sludge age becomes longer. When F/M is kept at a low value, the growth of activated sludge is close to zero, which reduces the treatment cost of excess sludge.
4) Convenient operation and management, and easy to realize automatic control. Because membrane separation can completely retain activated sludge in the bioreactor, and the hydraulic retention time (HRT) and sludge retention time (SRT) in the bioreactor are completely separated, it can be flexibly and stably controlled. At the same time, it is very easy to realize automatic control and improve the automation level of sewage treatment.
3. Comparison with related products:
1) treatment process and characteristics comparison
(1) air flotation-filtration process
Raw water → grille → regulating tank → coagulation and air flotation → filtration → disinfection → reclaimed water.
A. Technical features: Physical and chemical treatment method, without problems of biological culture and maintenance. The equipment has the advantages of small volume, small floor space, intermittent operation and convenient management.
B ... Scope of application: buildings with low concentration of organic matter in raw water (CODcr≤ 100mg/L, BOD5≤50mg/L, LAS≤4mg/L), fluctuating occupancy rate or intermittent use, especially suitable for high-end apartments and hotel bathing wastewater in seasonal tourism. (2) Biological contact oxidation treatment process
Raw water → grid → regulating tank → biological contact oxidation → precipitation → filtration → disinfection → reclaimed water.
Technical characteristics: Biological contact oxidation is a mature and practical treatment process. Strong adaptability to raw water, economical and practical, convenient operation and management, and low requirements for operation and management level.
B scope of application: the process has a wide range of applications, and is suitable for miscellaneous drainage, domestic sewage and secondary effluent.
(3) Membrane bioreactor treatment process
Raw water → regulating tank → pretreatment → membrane bioreactor → disinfection → reclaimed water.
A. Technical features: The membrane bioreactor is equipped with microfiltration membrane in the aeration tank of activated sludge process, which replaces the secondary sedimentation and subsequent filtration devices, and completes biochemical and physicochemical treatment in the same tank, which has a certain barrier effect on bacteria and viruses in raw water. The process has the advantages of strong impact load resistance, high removal efficiency of organic pollutants, good effluent quality, compact structure, less land occupation, less sludge output and high degree of automatic management.
B. Scope of application: Membrane bioreactor is mainly used in reclaimed water system with domestic sewage and miscellaneous drainage with high organic concentration as raw water.
2) Economic analysis
(1) The economic situation of reclaimed water project is directly related to the scale of reclaimed water project. The treatment scale is large, the investment index and operating cost of sewage treatment per cubic meter are relatively low, and it is easy to obtain better economic benefits.
(2) Construction cost and operation cost of reclaimed water project
4. Key points of construction and installation:
1) The construction, installation, acceptance, pipeline pressure test and leakage test of reinforced concrete structures shall be carried out according to the current codes such as GB50 14 1, GB50242 and GB50268.
2) Pipes of treatment equipment shall be installed straight, with reasonable layout and no leakage. Pipeline installation and connection shall comply with the provisions of relevant specifications. The installation of sewage pump should be stable and firm, and there should be no abnormal vibration during operation.
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