Purity in Every Drop: Solutions for Surface Water Drinking

Innovative Approaches for Making Surface Water Safe to Drink

Figure 1 Innovative Approaches for Surface Water

Design Scope

NEWater’s design scope mainly includes:

  • Selection of water treatment processes
  • Design of process parameters
  • Pieces of water treatment equipment
  • Internal piping connections for water treatment projects
  • Equipment foundation design
  • Selection of related auxiliary materials

It does not include the design of:

  • Electrical and automatic control systems for water pumps
  • Pipelines outside of the water treatment system
  • Sewage pipelines and backwash water supply pipelines outside of equipment installation foundations

Selection of Treatment Process and Determination of Treatment Flow

Figure 2 Selection of Treatment Process and Determination of Treatment Flow

The water supply project belongs to the category of tap water supply projects. It requires a short project cycle, a small footprint for the water treatment project, easy management, simple operation, and flowing water quality to meet the standards for tap water.

Based on many years of experience in water treatment engineering and the specific circumstances of this water supply project, our company believes that an integrated water treatment process should be used.

Figure 3 Integrated water treatment process diagram

The raw water source is river water, which is lifted by a water pump and enters the integrated water treatment equipment for treatment. After purification, the clean water flows into the clear water tank by gravity, utilizing the original pressure. 

For water supply, the clean water in the clear water tank can be lifted by a secondary pump for supply. The water treatment process is designed to be integrated and fully gravity-fed, which not only saves operating costs but also facilitates management.

Process Flow

Figure 4 Process Flow

1. Inlet

The raw water is introduced into the integrated water treatment equipment through the inlet using gravity flow, with the water pressure at the inlet maintained at 6-8 meters higher than the equipment’s foundation for proper water supply. The inlet flow rate is set at 500 tons but may fluctuate due to changes in river water level. To maintain stable operation and optimal treatment results, it is important to carefully adjust the total inlet valve flow rate of the water treatment equipment to ensure that the incoming water quantity falls within the required range.

2. Coagulation

A coagulant, such as poly aluminum chloride (PAC), is added at the inlet of the HC-integrated water treatment equipment and thoroughly mixed using a static pipe mixer, creating optimal conditions for the coagulation reaction. Coagulant dosage tests based on water samples are conducted to determine the optimal dosage of 515 g/m3 for this river water purification project undertaken by NEWater.

In case of changes in river water quality due to rainfall, the coagulant dosage should be adjusted accordingly. The coagulant is prepared as a 5-10% solution, mixed evenly using a mixer, and then precisely dosed into the inlet pipe through a metering pump, which can be adjusted using a flow regulating valve to ensure effective coagulation while minimizing coagulant usage.

Our HC gravity-type water treatment equipment adopts an advanced three-stage flocculation reaction process: packing baffle reaction process, grid reaction process, and folded baffle reaction process.

Figure 5 Coagulation process

  • Packing baffle reaction process: It uses hollow ball packing filled between the baffles to rapidly and vigorously mix the flocculant and water mixture, creating a good stirring effect.
  • Grid reaction process: The core part of the entire flocculation reaction process, with a reaction time of 6 minutes. The horizontal double-layer grid is used to change the flow rate of the water and create a turbulent flow state to improve the reaction effect.
  • Folded baffle reaction process: The water treatment equipment uses parallel folded baffles to promote collision and adsorption between flocculated particles. The baffles are designed to gradually decrease in cross-sectional area as the water flow rises, increasing the probability of collision and forming larger particles that can easily settle. The reaction time for this process is 6 minutes, and the water then flows through uniformly distributed water distribution devices at the bottom of the settling tank before entering the settling tank for further treatment.

The coagulation process in the water treatment equipment involves the collision and aggregation of micro-flocculent particles to form larger and more stable flocs, which can settle and separate easily. To achieve an optimal coagulation effect, appropriate energy is provided to the water flow to increase collision opportunities without causing floc breakdown. NEWater controls the water flow between the perforated plates and reaction fillers in the coagulation reaction zone to enhance particle collision and shorten the coagulation time, which is typically within 12-14 minutes.

In the later stage of the coagulation process, coagulation bodies with good settling properties formed in the water. The water flow cross-section gradually decreases as the water flows upward, which further increases the collision between coagulation bodies and promotes the formation of a coagulation sludge layer. This sludge layer absorbs suspended solids, colloids, and dispersed coagulation bodies in the water, improving the overall purification effect of the water treatment process.

3. Inclined Tube Sedimentation

Figure 6 Inclined Tube Sedimentation

According to the “shallow theory,” increasing the surface area of the sedimentation tank can improve the sedimentation effect. Our company uses hexagonal honeycomb inclined tube components installed in the sedimentation tank, forming numerous shallow pools, greatly increasing the surface area of the sedimentation tank, and improving the sedimentation effect. Through the sedimentation process, the main purpose is to remove the floc particles in the water and achieve solid-liquid (clean water) separation, reducing the burden on the filtration process.

4. Slanted-tube sedimentation

Our company uses hexagonal honeycomb slanted-tube components in the sedimentation tank to increase its surface area and improve sedimentation efficiency, based on the “shallow theory.” The water distribution system ensures even flow distribution for sufficient sedimentation effect. Moreover, a double-layer inclined tube sedimentation process with bottom auxiliary inclined tubes is adopted, effectively improving the removal efficiency of solid suspended particles and flocculated particles from the water, and reducing the workload of the filter tank.

The effluent from the sedimentation tank is collected by a uniformly distributed submerged effluent trough, which flows into the main effluent channel and then evenly enters six distribution boxes, each connecting to a separate filter tank. NEWater has designed a stainless steel submerged effluent trough with adjustable stainless steel outlet baffles to prevent epoxy resin from falling off and corrosion. The sedimented sludge is collected in a sludge hopper, further concentrated, and drained to increase sludge concentration and reduce water consumption. The sludge is discharged to the drainage ditch through a perforated pipe with manual sludge control valves for manual discharge, and small to medium-sized water treatment plants generally do not require further treatment for sludge before direct discharge into the municipal sewage network.

 5. Filtration

  • Filtration is an important step in water treatment to further improve water quality by removing smaller particles that may not be effectively removed by sedimentation. The filtration unit typically contains quartz sand filter material which can filter out flocs and colloids in the water, and adsorb them in the pores to form an adsorption layer, improving the removal rate of impurities.
  • NEWater’s integrated water purification equipment uses a gravity-based valveless filtration process, which utilizes the hydraulic siphon principle for automatic control of filter backwashing without additional equipment. This achieves automatic control and saves investment costs and operating expenses.
  • The filter tank is a fully enclosed square container with an internal layer of quartz sand filter material. The water inflow enters the filter tank through a built-in water distribution bend and the outflow is collected by a filter water cap uniformly distributed on the filter plate and discharged into the clear water pool above the filter tank. An overflow groove controls the water level in the clear water pool.

Figure 7 Interconnected filter tanks

  • NEWater’s integrated water purification equipment uses 5-6 interconnected filter tanks to ensure minimal changes in the backflushing water level and sufficient water volume, reducing backflushing time and improving the efficiency of the water purification equipment. The equipment is also equipped with an automatic siphon backwash control device that allows users to adjust the backwash time according to actual operating conditions, reducing water consumption and facilitating equipment operation and maintenance.

In addition, NEWater has made improvements to the design of their equipment based on feedback and user experience, including the addition of inspection ports for easy observation and maintenance of the filter at the bottom of the filter tank, ensuring smooth operation and maintenance after replacing the quartz sand.

6. Water Output

The integrated water purification equipment can flow into the clear water tank by itself (the inlet of the clear water tank should not be higher than 2m above the equipment foundation to satisfy the self-flow condition). After purification, the disinfected water is put into the clear water tank. A chlorine dioxide generator is used for disinfection (users can choose their own brand).

Figure 8 Integrated water purification equipment

To prevent chlorine dioxide leakage and avoid safety accidents, the chlorine dioxide dosing area is separately set around the clear water tank, with an area requirement of more than 20m2. The water in the clear water tank is pumped up by a lift pump and delivered to the enterprise’s circulating equipment through a secondary pressure pipeline.

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