摘要
焦化废水含有大量氮杂环化合物和多环芳烃等难降解有机毒物,传统生物方法对其处理效果不佳,往往使系统出水难以稳定达标,向原有系统中投加针对性强的高效菌作为一种常用的生物强化手段,可以有效解决这一难题,已经开始应用于各大焦化厂废水处理系统。本课题组根据武钢焦化废水的水质特点,将课题组筛选的高效菌应用于武钢焦化公司A/O中试装置,进行生物强化研究。
研究结果表明:结合了高效菌技术的A/O工艺对有机物和氨氮去除效果良好,在中试系统稳定运行期间,当系统进水COD浓度为1000～1700mg/L时,系统对COD的总去除率最高可达到95%,出水COD浓度可以控制在150mg/L以内,多数情况下可低于100mg/L;当进水氨氮浓度为100～300mg/L时,氨氮脱除率可超过97%,出水氨氮可低于10mg/L,出水混凝后COD和氨氮均达到国家一级排放标准(GB8978-1996)。
系统稳定运行期间,缺氧池反硝化运行效果良好,在没有外加碳源的情况下,反硝化率达到50%～74%,缺氧池的COD脱除率占到20%～42%,反硝化脱氮效果越好,越有利于COD在缺氧池中的去除。系统回流比为3时较为适宜,回流比超过3时,缺氧池溶解氧上升较快,不利于反硝化的正常运行。缺氧池进水NO_3~--N/C小于0.147时,缺氧池反硝化率与NO_3~--N/C比值呈正相关关系,当NO_3~--N/C大于0.2时,反硝化碳源相对不足,此时硝酸氮浓度越高,缺氧池反硝化率越低。缺氧池适宜pH范围为7.2~7.8。
好氧池进水COD/NH3-N低于4时,硝化反应运行效果较好,氨氮去除率高于95%,好氧池硝化反应对高负荷有机物适应性强,当好氧池进水COD高达1100mg/L左右,COD/NH3-N超过5.7时,氨氮去除率仍可达到90%左右。好氧池水力停留时间不应低于36h,进水中氨氮浓度低于260mg/L时,氨氮和亚硝酸盐去除效果均较好,硝化反应可处于较高的运行水平。当pH值为6.8~7.8范围内变化时,可满足氨氧化反应对pH值的要求。好氧池溶解氧不足会导致亚硝酸氮积累现象的出现,中试装置的曝气量低于25m3/h时,系统出水亚硝酸氮累积率最高可以达到50%以上,当曝气量恢复至60m3/h时,亚硝酸氮积累现象消失,好氧池稳定运行期间,氨氮主要转化为硝酸盐,亚硝酸盐的积累并不持久。
Coking wastewater contains abundant refractory organic toxicants, such as heterocyclic compounds、PAHs and so on, which was unable to disposed effectively by conventional biological methods, thereby making the quality of effluent substandard. Dosing pertinent and efficient bacterium as a kind of common biological reinforcement can solve the aforementioned problem viably, which has been widely applied to various coking wastewater treatment plant. According to the quality and characteristics of WISCO coking wastewater , our research group used high effective bacteria which had been isolated in lab to purify coking wastewater within Anoxic/Oxic pilot plant on the site of WISCO coking factory. This paper focus on the study of biological strengthening in this pilot plant.
Research results show that: organic pollutants and ammonia nitrogen can be removed availably by A/O process which combined with efficient bacterial technology. On the condition of stable running, total removal percentage of COD reach 95% while the influent’s COD concentration was within the range of 1000~ 1700mg/L, the effluent’s COD concentration was controlled under 150mg/L, in most cases, which was lower than 100mg/L. The removal percentage of ammonia nitrogen exceeded 97% during its influent concentration fluctuated between 100mg/L and 300mg/L, the concertration in effluent was less than 10mg/L. The effuent concertration of COD and ammonia nitrogen can reach the discharge standard (GB8978-1996).
During the stable running of systerm, the result of denitrification was excellent in anoxic tank. Without additional carbon source, denitrifying rate reached within 50%~74% as well as the removal rate of COD undulated between 20% and 42%, the more denitrifying rate increased, the more COD removed. The reflux ratio of anoxic tank at 3 was suitable, dissolved oxygen concentration was mounting if the reflux ratio outnumber 3, which means denitrification suffer adverse impacts. Denitrifying rate was positive correlated with NO_3~--N/C while the ratio of NO_3~--N/C below 0.147, on the contrary, denirtrifying rate descended if NO_3~--N/C surpassed 0.2, in other words, carbon sources was insufficient. The suitable value of pH in anoxic tank was within the range of 7.2~7.8.
Nitrification of aerobic tank was robust while COD/NH3-N below 4, ammonia nitrogen removal efficiency outstriped 95%, meanwhile the removal rate of NH3-N attained 90% when influent concertration of COD reached 1100mg/L and COD/NH3-N beyond 5.7, which means nitrification can bear high load organic pollutants. The optimal condition of nitrification was at HRT>36h, NH3-N<260mg/L, pH=6.8~7.8. Dissolved oxygen deficiency make phenomenon of the nitrite accumulation emerged, when the aeration volume under 25m3/h, the nitrite accumulated rate reached to 50%, but nitrite accumulation vanished finally due to the aeration volume recovered at 60 m3/h. During the stable running of aerobic tank, ammonia nitrogen was oxidized to nitrate, and nitrite accumulation was not durable.
引文
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