Low-carbon Nitrogen Removal For High Ammonia Textile Mercerization Wasterwater By Zeolite Sequencing Batch Reactor

A textile company in Guangdong province adopts liquid ammonia mercerization to replace the traditional liquid alkali mercerization.The handle,luster and brightness of the fabric are greatly improved by the liquid ammonia mercerization.However,a large amount of liquid ammonia was used in the process of liquid ammonia mercerization.While the ammonia gas was inevitably escaped from the mercerization process.To control the ammonia gas pollution,sulfuric acid was used to absorb the escaping ammonia gas.Thus,the liquid ammonia wastewater was produced as ammonium sulfate.This study explored the nitrogen removal treatment process to dispose the high ammonia liquid ammonia mercerization wastewater with low carbon.The"nitritation-denitrification process"and"partial nitritation-anaerobic ammonia oxidation process"were constructed to denitrify the raw water of liquid ammonia mercerization wastewater.The key of these two nitrogen removal processes of low carbon were the stable nitritation of ammonia wastewater.Therefore,stable nitritation base on zeolite-sequence batch reactor?ZSBR?,firstly,was studied in the study.Through the adsorption and desorption of ammonia nitrogen by zeolite,the stable nitritation of high ammonia wastewater was realized by controlling free ammonia?FA?in the reactor.Based on it,the stable and efficient partial nitritation was achieved by controlling the applied alkalinity while the liquid ammonia mercerization wastewater was diluted by the water of secondary sedimentation tank.Then ZSBR was combined with upflow sluge blanket reactor?USB?and upflow anaerobic filtration bed reactor?UBF?to treat liquid ammonia mercerized wastewater.Prospectively,with the study of the nitrogen removal efficiency,influencing factors and stability of the two nitrogen removal processes,theoretical support was put forwarded for the transformation of wastewater nitrogen removal engineering in the water purification center of the company.The results of this study are summarized as follows:?1?Stable nitritation experiment of ZSBR:At the start up stage of nitritation,the feeding water of ZSBR was liquid ammonia mercerization wastewater diluted by tap water.Stable nitritation was achieved after 23 cycles.With the running of the reactor,the nitrogen removal loading of ZSBR increased continuously.It was feasible that achieved nitritation of liquid ammonia mercerization wastewater by changing feeding ratio of ZSBR while the ammonia concentration of feeding water was 1490 mg/L and effluent water was 20 mg/L.The average nitrogen removal rate?ARR?of ZSBR effluent water was 0.86 kg N·m^-3·d^-1,while the highest ARR was 1.16 kg N·m^-3·d^-1.And average NAR was 97.22%.It was found that zeolite played the role of adsorption and desorption of ammonia nitrogen in ZSBR reactor through the analyzing of single cycle operation of ZSBR.Zeolite was used to maintaining the high free ammonia?FA?concentration in ZSBR.The main reason of rapid start-up of nitritation in ZSBR was the high FA concentration on the surfacce of zeolite.In the case of high ammonia nitrogen in liquid ammonia mercerization wastewater,the concentration of nitrite in ZSBR effluent nitritation water will gradually accumulate.The serious inhibition of ammonia oxidizing bacteria?AOB?was observed when the concentration of nitrite over 1800 mg/L.Similarly,if the concentration of free nitrite?FNA?exceeded 0.1 mg/L,AOB was inhibited to a certain extent,but the inhibition on AOB was short-term and reversible.?2?Stable partial nitritation experiment of ZSBR:Trying to achieve partial nitritation of raw water of liquid ammonia mercerization wastewater will eventually lead to the collapse of ZSBR reactor.The concentration of ammonia nitrogen changed to 300mg/L after dilution of the raw water of liquid ammonia mercerization wastewater with the effluent of secondary sedimentation tank.Stable partial nitritation?NAR>99.00%?was achieved by controlling applied alkalinity and adjusting aeration time.NO₂^--N/NH₄⁺-N of effluent was 1.1?1.4,stably.Instead of FA,free nitrite?FNA?was the main factor to inhibit NOB in partial nitritation experiments.As the concentration of the influent base decreased,the nitritation loading in ZSBR was reduced,with an average NPR of 0.66 kg N·m^-3·d^-1.?3?Two new nitrogen removal processes:The quality of effulent water of nitritation-denitrification was satisfactory when the glucose was used as carbon source and the ratio of carbon to nitrogen was 3:1.The nitrite removal rate over 95%and COD removal rate over 85%.Total nitrogen removal rate of USB was 4.0 kg N·m^-3·d^-1.The n itrogen removal effects of different carbon sources and different carbon-nitrogen ratio USB were analyzed.It is confirmed that the optimal carbon-nitrogen ratio of glucose was 2.5:1,and that of sodium ethanolacetate was 2:1.Considering the comprehensive cost and the actual situation,the water purification center should adopt glucose as denitrification plus carbon source.Partial nitritation-anaerobic ammonia-oxidation?ANAMMOX?process can be successfully used to denitrify diluted liquid ammonia mercerization wastewater.The total nitrogen loading of UBF can reach up to 0.82 kg N·m^-3·d^-1,and the total nitrogen removal rate is over 70%.The best base ratio of ANAMMOX is 1.2.According to the economic analysis of the two low carbon nitrogen removal processes,the cost of treating liquid ammonia mercerization wastewater by nitritation and denitrification process is 30.18 yuan/kg N,while the cost of partial nitritation and anaerobic ammonia oxidation process is only 8.21 yuan/kg N.?4?The inoculation sludge and culture sludge of ZSBR and USB were analyzed,the result suggested that:With the operation of ZSBR and USB,nitrifying bacteria in ZSBR were continuously proliferated.The relative abundance of AOB on the genus level reached 54.78%,while the NOB was almost completely washed out of ZSBR.The relative abundance of denitrifying bacteria in USB increased from 4.77%to 64.17%.In UBF,there might exist three kinds of denitrification process:nitritation,partial denitrification and anammox.