Diatomaceous earth is a natural opal containing crystalline water and amorphous silica. It is of great use in sewage treatment. It has strong adsorption, nano-pores and other characteristics, making it easy to drain water. The effect is stable, and the chroma, COD, total P, and SS can all meet its requirements. This process also has many advantages such as small footprint and low investment. It is a patented technology. However, its disadvantage is that it does not handle ammonia nitrogen well, so it needs to be combined with traditional biochemical treatment, but the residence time is shorter than traditional ones.
The use of diatomite for modification and application in sewage treatment was reported both domestically and abroad as early as the early 1980s. This is a unit technology that can only conditionally remove pollutants in sewage under certain conditions. Therefore, this unit technology has certain advantages compared with other similar flocculation adsorption technologies. Therefore, in recent years, many environmental protection companies and local governments hope to use diatomaceous soil water treatment technology to treat urban sewage up to standard in one go and directly reuse it. As a result, this goal was not achieved.
For example: Inner Mongolia's daily treatment of 10,000 tons was implemented in 2001: when the water quality concentration was low, BOD and COD met the standards, but ammonia nitrogen and total phosphorus did not meet the standards.
Qingyuan’s daily treatment of 10,000 tons implemented in 2002: ammonia nitrogen and total phosphorus did not meet the standards.
Haimen’s daily treatment of 10,000 tons was implemented in 2003: the water quality concentration COD can reach the first-level standard when the water quality concentration COD is 200mg/L, and its ammonia nitrogen has already reached the standard.
The above projects show that it is difficult to fully meet the discharge standards for urban sewage treatment using only a single conventional diatomite technology, especially since diatomite does not have a denitrification function. Even if it is combined with biochemical technology, it is scientific and rational.
Comparison of several diatomaceous soil water treatment technologies and biochemical technology composite processes
(1) Diatomaceous soil water treatment technology + contact oxidation technology
1. The removal of COD and BOD is ideal; 2. The removal effect of ammonia nitrogen and total nitrogen is not ideal; 3. The investment is not economical; 4. The amount of sludge is large;
(2) Diatomaceous soil Water treatment technology + BAF technology
1. The removal of COD and BOD is ideal; 2. The effect of removing ammonia nitrogen is ideal, but the effect of total nitrogen removal is poor; 3. The investment is high; 4. The amount of sludge is large ;
(3) Diatomaceous earth water treatment technology + other complete biochemical technologies, even if the effluent water quality can be relatively ideal, the investment cost is high and the investment advantage cannot be reflected.
(4) If biochemical technology is placed first and diatomaceous soil water treatment technology is placed behind for in-depth treatment, their respective advantages can be brought into play at the same time, and the advantages can complement each other. As a result, not only the water quality indicators of COD, BOD, N, P, and SS have reached Class A standards stably (the effluent can meet the reuse requirements), but it also saves investment, low operating costs, and takes up less space. That is to say, it can truly reflect the characteristics of "high efficiency and low consumption". In recent years, Nanjing Jiaqing has successfully implemented six urban sewage treatment projects, fully proving the correctness of this view.