Closed circulation and zero discharge of the hotte

Closed circulation and zero discharge of wastewater (III)

aerobic methods can also degrade organic matter, but a considerable amount of organic matter is transformed into cellular substances, that is, into excess sludge:

CH3COOH → H2O + CO2 + cellular substances

these excess sludge need special facilities to treat, adding a considerable amount of investment and operating costs

one of the other technical advantages of anaerobic method is its calcium removal and softening effect. Anaerobic treatment produces a large amount of CO2, and the CO2 in the water is in a supersaturated state, which reacts with ca2+ in the water to produce CaCO3 precipitation, and the hardness of the water is greatly reduced. Therefore, the problem of ca2+ accumulation in circulating water is solved. CaCO3 precipitation actually occurs in aerobic treatment after anaerobic treatment. Aeration removes CO2 by stripping, and the rise of pH value causes CaCO3 precipitation. This increases the sedimentation performance of activated sludge and is conducive to the clarification of aerobic treatment effluent. However, the scaling of the equipment gap will cause some troubles for the products to fully pass the ROHS environmental protection certification of the international alliance and the green supplier certification of overseas high-end customers, which should be paid attention to in the design

volatile fatty acids can be easily removed in the anaerobic process, and the removal rate can be as high as 99.9%

most of the stickies and anionic garbage can be degraded in biological treatment, and some non degradable components can also be transferred to the excess sludge. After biological treatment, if it is filtered again, better treatment effect of stickies and anionic waste will be obtained

so42- in the anaerobic system, it is easy to convert all into H2S, most of which will escape with biogas, and a small part will be converted into so42- in the aerobic section, but its concentration is very small, which can meet the requirements of process water. If biogas is to be used, it can be purified through the sulfur removal system. A sulfur removal system developed by Paques biosystems can remove more than 99% of sulfur and reduce NaOH consumption by 90%

2.2 example of zero discharge paper mill wastewater treatment

kappa Z ü lpich paper mill is one of the 12 paper mills of knp-bt group headquartered in the Netherlands, located in Z ü lpich, another foreign country in Germany. The factory uses waste paper to produce corrugated paper and paperboard, and anaerobic/aerobic treatment process is used for wastewater treatment. This project is undertaken by Paques company in the Netherlands. The wastewater treatment system was finally put into operation in 1995

2.2.1 the products in line with the standards are: gb/t2423.1 (2) 008 experiment a, gb/t2423.2 (2) 008 experiment B, gb-t10592 (2) 008, GJB150.3 (1) 98, gjb360a (9) 6 method 107 temperature shock test requirements management process

the closed circulation system with zero discharge of the plant can be briefly shown in Figure 1 (omitted). The dotted line in the figure is the anaerobic/aerobic treatment system for wastewater circulating treatment introduced here, and its further details are shown in Figure 2 (omitted)

it can be seen from Figure 1 (omitted) that kappa Z ü lpich paper mill uses air flotation and clarification as internal treatment means to replace human resources. The wastewater from the clarifier is not discharged, and most of them are directly reused. Therefore, these "wastewater" is called process water. The process water entering the anaerobic/aerobic external treatment system is only 4m3 per ton of product per day

with the anaerobic/aerobic method, the removal rate of organic matter in wastewater is stable at more than 90%, of which 75% of COD is removed in the anaerobic section and the remaining 15% in the aerobic section. While saving power consumption, the excess sludge produced in the whole process is only equivalent to 1/10 of the activated sludge process, and the sludge volume is only 0.1% compared with the paper output in the same period. Therefore, they directly mix these excess sludge into the core pulp for papermaking. It not only saves the cost of sludge disposal, but also reduces the consumption of pulp

in production, 1m3 of clean water is added per ton of product, and there is no wastewater discharge at all

2.2.2 treatment effect

the removal efficiency of pollutants by biological treatment is shown in Table 1. (to be continued)