Xingye Leather Technology Co., Ltd. has vigorously introduced advanced equipment, implemented clean production technology, and used environment-friendly chemical materials. The policy of five-water separation and respective treatment has been practically implemented and the A/O process and high-efficiency microbial treatment technology has been adopted, which thoroughly solves the problem of ammonia and nitrogen standard exceeding and fully realizes the emission standard.

The company attaches great importance to energy saving, emission reduction and recycling. In combination with the actual production and environmental protection, the company has highlighted the construction of reclaimed water reuse system, taken the lead to adopt advanced technology of ultrafiltration and reverse osmosis membrance treatment in the tanning industry to carry out advanced treatment, thus greatly improving the reuse rate of reclaimed water, with a reuse rate of more than 50%.

1Multi Medium Technology

The head drain tank flows the discharge water from the existing biochemical treatment system into the feed pump of the multi medium filter through the side discharge pipe, and then into the multi medium filter after the rising of pressure. The multi medium filter adopts the carbon steel lining rubber tank, in which different filters such as pebbles and quartz sand are placed in layers. When wastewater passes through the filters, impurities such as colloids, sediments and cenobiums from the biochemical precipitation process can be removed by the formation of cake layer through the colliding and intercepting on the surface of the filters. The technological characteristic of multi medium is to remove the residual solid wastes and part of the colloids in the biochemical precipitation process to reduce the subsequent processing load. The water produced in multi medium filter enters the sand filter for further treatment by the UF system.

The starting procedure of backwash frequency and time of multi medium is set by PLC, and the water produced shall be used regularly for backwash. The backwash water will be discharged into the backwash wastewater tank.

2Ultrafiltration Technology

The wastewater is bumped by a new feed bump of the ultrafiltration membrane treatment system from the sand filter. A bag security filter is set up before the wastewater enters the membrane of the ultrafiltration system to intercept impurities such as large pieces of residual scum and penetrating filter materials to prevent them from damaging the membrane layer. Under the pressure of the lifting pump, the wastewater enters the membrane modules and the inner side of the membrane from the outer side of the hollow membrane filament. The ultrafiltration system is operated by full filtration. All the water produced enters the ultrafiltration tank, while the fine colloidal pollutants are contained in the wastewater are intercepted on the outer surface of the membrane filament.

The ultrafiltration backwash is set periodically by time, with once in 30-60 minutes. Through the UF backwash pump, the water produced in ultrafiltration enters from the water-producing side of the UF membrane, and the sediments on the membrane surface will be reversely flushed in order to restore the performance of UF membrane.

The whole ultrafiltration system is designed for fully automatic control, and the program is set for normal filtration, gas and water backwash and on-line chemical cleaning. The backwash water can return to the front regulating tank and reenter the wastewater system for retreatment to reduce external drainage. The ultrafiltration system is also equipped with off-line chemical cleaning system, which can perform chemical cleaning on the membrane modules without the detachment from the equipment.

3 Reverse Osmosis Technology

The ultrafiltration water is lifted into the 25um safety filter through a reverse osmosis pump, and then enters the reverse osmosis membrane with a certain pressure and flow provided by the high-pressure pump. Acid and alkali are added into the inlet water of the reverse osmosis membrane to adjust pH, while scale inhibitor and reducing agent are added to ensure the stable operation of the reverse osmosis system and improve the ion interception of the reverse osmosis membrane. After the reverse osmosis membrane intercepts most of the organic matters and salt, and then the permeate naturally flows into the reuse water tank.

Reverse osmosis system control also adopts fully automatic control, and carries out filtration and water production, dosing, machine halt flushing and online CIP cleaning according to the program. In the design of reverse osmosis system, the membrane modules are placed in the outer membrane tube (pressure vessel), and are arranged in series-parallel connection to achieve the lowest power consumption and component water balance according to the requirement of the inflow and output of the membrane.