E-Mail:ytbangda@foxmail.com
Tel:+86-535-6801125
With the growth of the economy and population, pollution of the natural environment has drawn increasing human concern. Building upon operational experience with existing wastewater treatment units, combined with our company's proprietary research and practical engineering expertise, we have developed an organic wastewater treatment system. This equipment incorporates advanced domestic and international technologies and manufacturing techniques from the late 1990s, with the main construction materials being FRP (fiberglass-reinforced plastic) and stainless steel. The system is designed to enable domestic sewage and industrial wastewater to meet discharge or reuse requirements as specified by the client.
This equipment is primarily used in residential communities (including villa estates), high-end hotels, hospitals, comprehensive office buildings, printing and dyeing mills, chemical plants, and other small-scale wastewater treatment facilities. The treated effluent quality meets the national Integrated Wastewater Discharge Standard (GB 8978). The entire system can be installed either underground or above ground, depending on site conditions.
1. The WSZ series wastewater treatment unit can be installed below grade, with the surface above available for landscaping. No additional building, heating, or insulation is required. It may also be installed above ground as site conditions permit.
2. The two-stage biological contact oxidation process utilizes patented aerators, eliminating the need for complex piping. Compared to activated sludge tanks, it has a smaller footprint, better adaptability to water quality fluctuations, stable effluent quality, and no risk of sludge bulking.
3. The sludge tank employs natural sedimentation, requiring sludge discharge only once every 3 to 8 months (via vacuum truck extraction or dewatering and off-site disposal).
4. The entire treatment system generally requires no dedicated operator; only periodic maintenance and servicing are needed.
5. The system exhibits strong adaptability to minor fluctuations in influent water quality.
6. No pressure vessels, air compressors, recirculation pumps, or similar auxiliary equipment are required, significantly reducing capital investment.
7. Low power consumption, minimal maintenance, and reduced manual intervention. As the WSZ process is aerobic, odor issues associated with sludge are effectively mitigated.
1. Hotels, restaurants, sanatoriums, hospitals, residential areas, etc.
2. Residential communities, villages, and towns.
3. Railway stations, airports, seaports, and vessels.
4. Factories, mines, military installations, tourist sites, and scenic areas.
5. Various types of industrial wastewater with characteristics similar to domestic sewage.
| Parameter | WSZ-0.5 | WSZ-1 | WSZ-2 | WSZ-3 | WSZ-5 | WSZ-50 |
| Standard Flow Rate (m³/h) | 0.5 | 1 | 2 | 3 | 5 | 50 |
| Design Influent BOD (mg/L) | 400 (common for all models) | |||||
| Design Influent COD (mg/L) | 800 (common for all models) | |||||
| Design Influent SS (mg/L) | 800 (common for all models) | |||||
| Design Influent NH₃-N (mg/L) | 500 (common for all models) | |||||
| Design Effluent (mg/L) | BOD ≤ 20, COD ≤ 50, SS ≤ 70, NH₃-N ≤ 15 |
The above models are standard configurations; custom designs are available based on specific client requirements.
The biological contact oxidation wastewater treatment system is designed to operate in conjunction with a civil engineering equalization tank. The civil works include the equalization tank and coarse screen, while the packaged equipment comprises the primary sedimentation tank (hydrolysis/acidification tank), contact oxidation tank, self-flotation sedimentation tank, disinfection tank, sludge tank, and blowers.
Descriptions of each tank's function and operating principle are as follows:
(1) Coarse Screen – Installed at the inlet of the equalization tank to intercept large suspended solids and debris from the incoming wastewater.
(2) Equalization Tank – Used to balance fluctuations in both flow rate and pollutant load from various sources. The equalization tank is typically constructed of reinforced concrete, with a storage capacity (effective volume) 8 to 10 times the average wastewater flow rate. Civil drawings are provided by our technical department, and construction and reinforcement are carried out by the client.
(3) Primary Sedimentation Tank (Anaerobic Tank) – This is the first stage of the packaged treatment unit. It contains elastic packing material that facilitates biofilm formation and is resistant to clogging. Wastewater from the equalization tank is lifted by a feed pump into the primary sedimentation tank, where effective microbial populations carry out digestion and denitrification, removing organic and inorganic suspended solids.
(4) Contact Oxidation Tank – Effluent from the primary sedimentation tank flows by gravity into the contact oxidation tank. This tank operates under pressure and is filled with suspended bio-carriers. Pressurized aeration dissolves oxygen into the water, promoting the proliferation of aerobic bacteria over a cultivation period of 15 to 45 days. These bacteria consume residual organic matter and insoluble inorganic suspended solids, while also facilitating phosphorus removal and aerobic digestion of excess sludge, thereby preventing sludge bulking.
(5) Self-Flotation Sedimentation Tank – Effluent from the aerobic tank flows into the self-flotation sedimentation tank, where solid-liquid separation is achieved using dissolved gases from the pressurized aeration system. No additional dissolved air flotation (DAF) system is required.
(6) Disinfection Tank (Clear Water Tank) – Effluent from the self-flotation sedimentation tank flows by gravity into the disinfection tank, where it is treated with chlorine dioxide generated by an on-site generator. The hydraulic retention time in the disinfection tank is 30 minutes (refer to the chlorine dioxide generator manual for details).
(7) Sludge Tank – Excess sludge from the self-flotation sedimentation tank, which has undergone aerobic digestion (activated sludge), is partially returned to the primary sedimentation tank, while the remainder flows into the sludge tank. Natural sedimentation occurs, with supernatant returned to the primary sedimentation tank. Residual sludge is extracted by vacuum truck every 3 to 8 months and dewatered for off-site disposal, or alternatively pumped out and dewatered.
This equipment is designed for integrated operation with the civil equalization tank. The equalization tank is constructed of reinforced concrete, with dimensions and the WSZ foundation layout provided by our company's engineering drawings. The client must prepare the equalization tank and foundation in accordance with the supplied drawings. An excavation width of at least 800 mm greater than the equipment footprint is required on all sides to facilitate piping installation.
Once the equipment is delivered, it should be positioned according to the installation drawings. A crane should be used to lower the WSZ unit onto the underground foundation. Care must be taken to ensure the correct orientation of the tank body. The flange marked "Inlet" on one end of the unit should align with the outlet of the equalization tank. Level the unit, align the inlet and outlet connections, and connect them with piping.
Depending on client requirements, the blower may be installed either inside the equipment enclosure or in a separate equipment room. After positioning the blower, connect a pressure relief valve to the blower discharge port, and route the outlet piping to the flange marked "Blower Connection" on the opposite end of the WSZ unit. After connection, check for air leaks. Once confirmed leak-free, proceed with electrical wiring: connect the blower using a three-core cable, with the other end connected to the terminal block marked "Blower" in the control panel.
The clear water outlet flange is located on the same end of the unit as the blower inlet flange. Connect piping to the clear water outlet flange. The treated effluent may be either discharged or reused (e.g., for toilet flushing, landscaping, and other non-potable applications) as determined by the client.
The level sensor is installed in the equalization tank and is used to control the feed pump, providing pump protection. The operating principle is straightforward: three single-strand copper wires are secured to a PVC pipe at high, medium, and low positions, with the other ends connected to the corresponding level control terminals in the control panel.
After installing the feed pump, determine the appropriate heights within the equalization tank. Position the low and medium level sensor leads 100–150 mm above the pump, and the high-level lead 100–200 mm below the overflow return port. When the water level reaches the high-level sensor, the feed pump starts, and the system begins operation. When the level drops to the low-level sensor, the pump stops, completing one operating cycle.
The feed pump is installed at the outlet end within the equalization tank, placed at the tank bottom and raised 150–200 mm on stones or bricks. Connect the pump discharge via a flexible hose to the outlet at the top of the tank, installing a tee connection. One branch serves as a return line to the bottom of the equalization tank for sludge mixing, while the other connects to the WSZ unit inlet. Ensure all connections are secure and leak-free. Connect the pump power cable to the "Wastewater Pump" terminals in the control panel. After all power connections are completed, proceed with trial operation.
After all installations are complete, power on the system and verify indicator lights. Turn the selector switch to "Manual" mode. Press the "Feed Pump" start button; check the pump rotation direction. If reversed, swap any two phase wires and restart. Next, start the blower and verify its rotation direction; if reversed, swap any two phase wires accordingly. Once all adjustments are verified, conduct a water flow test to confirm no leaks at any connection point. After confirming leak-free operation, backfill the voids around the equipment with soil and level the ground. Ensure the finished grade prevents rainwater ponding. The system drain line should be at least 0.6 m below the finished grade. Do not place heavy objects above the unit; install appropriate warning barriers to prevent vehicle traffic. Once the unit is filled with water, avoid draining it completely to prevent buoyancy issues due to groundwater.
Before commissioning the activated sludge treatment system, ensure that all water treatment equipment, process piping, and electrical systems have been installed and tested, and that the system is ready for water intake and operation.
1. Basic Theory
Before formal commissioning, the primary task is to cultivate and acclimate the activated sludge.
Sludge cultivation involves providing optimal conditions for the growth and reproduction of microorganisms and bacteria—including adequate nutrients, oxygen supply (aeration), suitable temperature, and pH—to promote rapid proliferation and the formation of activated sludge at the required concentration for wastewater treatment.
Sludge acclimation refers to adapting the cultivated sludge to the specific quality and quantity of the wastewater to be treated. During acclimation, two key microbial changes occur: (1) microorganisms capable of degrading organic pollutants in the wastewater increase in number, while those unable to do so gradually die off; and (2) surviving microorganisms produce induced enzymes that enable them to break down the organic compounds present in the wastewater.
Three common methods for activated sludge cultivation and acclimation are: asynchronous cultivation and acclimation, synchronous cultivation and acclimation, and seeded cultivation and acclimation.
Asynchronous – Cultivation is carried out first, followed by gradual acclimation to the target wastewater.
Synchronous – Cultivation and acclimation proceed simultaneously or in alternating stages.
Seeded – Excess sludge from another wastewater treatment plant is used as an inoculum, followed by further cultivation and acclimation.
Healthy activated sludge has a fluffy, cotton-like appearance, is yellowish-brown in color, and exhibits good settling properties, with a slight earthy odor.
When the influent organic load is low, the sludge appears dark brown, similar to that from municipal treatment plants, with large, fluffy flocs that are clearly distinguishable from the water phase.
When the influent organic load is high, the sludge turns yellowish-brown, with very fine, dispersed flocs that blend into a viscous, homogeneous mixture, reducing filterability.
2. Sludge Cultivation and Acclimation – Seeded Method
This treatment system uses a membrane bioreactor (MBR), which combines the purification effect of activated sludge with membrane separation. Therefore, the activated sludge system must be properly commissioned to achieve effective treatment performance.
The influent to this system is primarily high-quality greywater with good biodegradability. Direct seeding, cultivation, and acclimation of activated sludge can be carried out accordingly.
Tel: +86-535-6801125
Tel: +86-13853509591
Email: gaobo@bondaequip.com
