外文翻譯--通過曝氣增加結(jié)晶以去除豬廢水中磷酸鹽、鈣及鎂（英文）

1、Water Research 36 (2002) 2991–2998Removal of phosphate, magnesium and calcium from swine wastewater through crystallization enhanced by aerationKazuyoshi Suzuki*, Yasuo Tanaka, Takashi Osada, Miyoko WakiWaste Recycling L

2、aboratory, National Institute of Livestock and Grassland Science (NILGS), 2 Ikenodai, Kukizaki-cho, Inashiki-gun, Ibaraki 305-0901, JapanReceived 15 February 2001; received in revised form 25 July 2001; accepted 4 Decemb

3、er 2001AbstractIn order to confirm the possibility of removing PO4-P, Mg and Ca from swine wastewater through artificial crystallization by aeration, laboratory and pilot scale experiments were carried out using actual s

4、wine wastewater. The pH of swine wastewater increased up to approximately 8.5 with continuous aeration, and a large part of the soluble PO4-P, Mg and Ca was crystallized. The ingredients of the crystals were estimated as

5、 MAP and HAP according to their mole ratio of NH4-N, PO4-P, Mg and Ca. The sedimentation speed of crystals in swine wastewater was about 3 m h?1, and over 90% of them had settled after standing 1 h. A pilot scale reactor

6、 with the dual functions of crystallization by aeration and settling was operated continuously using actual swine wastewater, with aeration conditions of HRT 4.1 h and 26 m3 air h?1 m?2 cross section (18 m3 air h?1 m?3 v

7、olume). During 50 days of operation, pH at the aeration column held stable at 8.0, and 65% of PO4-P, 51% of Mg, and 34% of Ca were removed. r 2002 Elsevier Science Ltd. All rights reserved.Keywords: Swine wastewater; Sca

8、le; Crystallization; Aeration; Magnesium ammonium phosphate; Settling1. IntroductionIn most swine-husbandry facilities in Japan, faeces, urine and the washing water from piggeries are separated into solid and liquid frac

9、tions after mechan- ical solid–liquid separation. The solid fraction is composted and utilized at farmland as a fertilizer. The liquid fraction (swine wastewater) is purified through a treatment process and discharged in

10、to public water bodies such as rivers, lakes and marshes. Strict standards for discharged livestock wastewater have been set to prevent eutrophication of such public water bodies. Therefore, swine farms are forced to pur

11、ify swine wastewater within the very strict limits imposed by law. To comply with the law, several methods for treatmentof swine wastewater have been investigated such as an intermittent aeration process [1–3], anaerobic

12、 treatment (UASB) plus a trickling filter process [4,5], and some of which are actually used in piggeries. However, there are some reports concerning the accumulation of scale in swine wastewater treatment plants [5,6].

13、Scale accumulates in pipes and pumps, and sometimes causes serious trouble at wastewater treat- ment plants [7]. In addition to PO4-P and NH4-N, swine wastewater also contains high concentrations of Mg and Ca [8]. Under

14、alkaline conditions, equal moles of Mg, PO4-P and NH4-N are crystallized, forming struvite (magnesium ammonium phosphate: MAP, MgNH4PO4 ? 6H2O) [7]. Ca also crystallizes with PO4 and forms, for example, hydroxyapatite (H

15、AP, Ca5OH (PO4)3) [9]. These crystals, especially MAP, are thought to be the main components of the scale in swine wastewater treatment plants [5,6,10]. Therefore, Mg, Ca and PO4-P causing the scale should be removed in*

16、Corresponding author. Tel.: +81-298-38-8676; fax: +81- 298-38-8606. E-mail address: szkazu@affrc.go.jp (K. Suzuki).0043-1354/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 3 - 1 3

17、5 4 ( 0 1 ) 0 0 5 3 6 - X2.5. Chemical analysisSwine wastewater was centrifuged at 3000 rpm for 10 min, and soluble components were analyzed. To determine the crystallized components, 5 N HCl was added to the swine waste

18、water at a final concentration of 0.1 N to dissolve the crystal, and was centrifuged at 3000 rpm for 10 min. after standing 30 min. The super- natant was analyzed for the determination of the soluble plus crystallized co

19、mponents. The concentrations of the crystallized components were calculated as the differ- ence between these amounts. PO4-P, NH4-N, Mg and Ca were measured using a standard method [17]. Total- N and total-P were measure

20、d by a flow injection analyzer (Sanuki Industrial), total-N was measured from the absorbance at 220 nm under HCl acid conditions after digestion with potassium peroxodisul- fate at 1401C, and total-P was measured from th

21、e absorbance at 880 nm by the molybdenum blue method after digestion with potassium peroxodisulfate at 1201C. The I-C was measured using I-C Analyzer (TOC 500 Analyzer, Shimadzu).3. Results and discussion3.1. Batch exper

22、iments for crystallization by aerationThe water quality of the swine wastewater used for the experiments is summarized in Table 1. Sampling was done 3–4 times each month for a total of 34 times between December 1999 and

23、October 2000. The moleratio of soluble components (PO4-P:NH4-N:Mg:Ca =1.0:7.5:0.9:0.7) was thought to be suitable for crystal formation [8]. As shown in Fig. 1a, by aeration with 13 m3 h?1 m?2(16 m3 h?1 m?3) the pH of sw

24、ine wastewater increased from 7.0 to 8.0 in 0.5 h, and reached 8.5 at the end of the period. The concentration of I-C, the indicator of CO2, in swine wastewater, was decreased remarkably, because of the stripping of CO2

25、from wastewater by aeration (Fig. 1b). The concentrations of soluble PO4-P, Mg and Ca in swine wastewater were also decreased remarkably with the rise in pH (Fig. 1c). This decrease was caused by the crystallization of s

26、oluble PO4-P, Mg and Ca. The changes in the concentrations of soluble and crystallized forms of PO4-P, Mg and Ca before and after 3 h of aeration are indicated in Fig. 2a–c. Most of these components existed in soluble fo

27、rm before aeration, but after 3 h of aeration, most were converted into the crystallized form. Two hours are thought to be enough for an aeration period for crystallization in swine wastewater, because the concentrations

28、 of soluble PO4- P, Mg and Ca in swine wastewater were decreased remarkably for the 2 h after beginning aeration, but there were only minimal changes in the concentrations of these components after 2 h (Fig. 1c). As show

29、n in Table 2, reduced aeration of 6.5 m3 h?1 m?2(7.9 m3 h?1 m?3) was not enough to either raise pH or crystallize PO4-P. On the other hand, aeration as high as 31 m3 h?1 m?2 (38 m3 h?1 m?3) would induce high pH (8.7), bu

30、t the efficiency of PO4-P crystallization was almost the same as for the case of aeration with 13 m3 h?1 m?2 (16 m3 h?1 m?3). Therefore, aeration withTable 1 P, N, Mg and Ca concentrations of swine wastewater from the NI

31、LGS piggeryComponents Mean n ¼ 34 mmol l?1 (mg l?1) SD min–maxP Crystallized PO4-P 0.7(22) 0.3 0.0–1.7 Soluble PO4-P 5.2(161) 1.0 3.5–7.8 Other P 0.4(12) 0.3 0.0–1.0 Total 6.3(195) 1.1 4.6–7.8N Crystallized NH4-N 2.

32、2(31) 3.3 0.0–10.1 Soluble NH4-N 39(543) 14 20.6–63.8 Other N 7.7(108) 5.0 0.0–15.9 Total 49(682) 11.0 30.5–65.0Mg Crystallized Mg 0.4(10) 0.5 0.0–0.9 Soluble Mg 4.9(119) 0.9 3.2–6.9 Total 5.3(129) 1.0 3.4–7.2Ca Crystall