污水处理领域磷回收技术及其应用

介绍了国内外从污水中磷回收研究与应用现状,多以含磷丰富的污泥脱水上清液、厌氧污泥消化液以及富磷废水为磷源,鸟粪石、磷酸钙等沉淀是目前广泛采用的回收形式。简述污水处理领域的磷回收技术有沉淀法,结晶法,电渗析法、离子交换等。沉淀法中鸟粪石、磷酸钙等的研究相对较为成熟,应用较多。最后展望了我国污水处理领域磷回收前景,2005年我国污水中的磷量相当于2000年全国磷矿开采量的42.7%,具有广泛的回收前景和环境经济效益。     

排水研究新热点--从污水处理过程中回收磷

磷是一种不可更新、难以替代的有限自然资源.因控制水体富营养化而实施的生物营养物去除为从污水中回收磷创造了条件,以鸟粪石等磷酸盐沉淀方式从处理过程中回收磷并用于肥料或磷酸盐制造业原料已成为排水界研究的新热点.基于第二届磷回收国际学术会议论点与结论,阐述了磷回收的基本概念、应用实例、污泥管理、应用技术、经济分析等方面的情况.     

黄河河道整治工程根石走失原因及防护措施

针对黄河河道整治工程根石走失严重这一问题，指出根石走失的原因主要是水流冲刷、根石埋置深度不足、根石断面形态不稳定和根石直径偏小等，提出了管护人员要加强工程管理与养护、对险情采取正确的抢护方法、主动进行根石加固等3种防护措施。     

龙头石水电站1号泄洪洞洞内水跃流态计算分析

对龙头石水电站1号泄洪洞洞内发生水跃的可能性进行了计算分析,并进行了试验验证,证明了本文的计算方法是切实可行的;同时,根据计算和试验结果,得到了龙头石水电站1号泄洪洞不同闸门开度下洞内不发生水跃的下游控制水位。     

欧洲城市污水处理技术新概念——可持续生物除磷脱氮工艺(上)

传统污水处理工艺以能消能 ,消耗大量有机碳源 ,剩余污泥产量大 ,同时释放较多CO2(因耗能 )到大气之中。当今 ,全球普遍强调的可持续发展经济模式在污水处理领域也得到体现。因此 ,研发以节省能 (资 )源消耗、并最大程度回收 (用 )有用能 (资 )源的可持续污水处理工艺已势在必行 ,在详细介绍两种新近在欧洲出现的可持续处理工艺———反硝化除磷、厌氧氨 (氮 )氧化的基础上 ,提出一个以转换有机能源 (甲烷 )、回收磷酸盐 (鸟粪石 )、回用处理水 (非饮用目的 )为目标的可持续城市污水生物除磷脱氮推荐工艺     

黄河下游丁坝根石走失的原因及防护措施

黄河下游丁坝根石走失是坝岸工程出险的主要原因。本文对丁坝根石走失的原因，从水流条件、根石断面形态等方面进行了分析和探讨。提出了管护人员应该对坝岸和基础情况、河势变化、险情判断、抢护方法等做到心中有数，使防护工作由被动变主动。同时着重指出抓发管理，注意正确防护是防止根石走失的有效途径。     

基于源分离的农村分散式生活污水处理技术

与城市集中式生活污水处理相比,农村分散式生活污水处理可以采用源分离技术与污水资源回收处理技术相结合的模式,从而有效回收污水中的营养盐、减少排放到环境中的污染物、提高水的循环利用效率。本文提出了三种源分离生活污水,包括尿液,灰水(洗浴、洗衣水等)和粪便。尿液不到家庭废水总量的1%,却含有50%～80%的氮、磷和钾等营养盐以及大部分药物和激素。粪便含有较高的有机物、固体和病原菌,并携带剩余的药物/激素残留物。灰水量最大,但是在三类污水中其营养盐、病原菌的含量最低,但含有洗涤剂和个人护理产品等污染物。提出了两种模式的生活污水源分离及污水处理技术。尿液的最佳处理技术是用鸟粪石沉淀法回收磷,用氨汽提法回收氨氮。黑水的最佳处理方法是厌氧消化;灰水的最佳处理方法是人工湿地和BAF、MBR等好氧生物处理技术。     

深厚砂砾石地层固结灌浆在实际工程中的应用

水利工程施工过程中,经常会遇到水工建筑物直接修建在砂砾石地层上,为了提高砂砾石地层的整体性、密实性并降低其透水率,一般需要对坝基采取全面的固结灌浆,必要时也在坝基上、下游一定范围内进行固结灌浆。结合水利枢纽的工程实践,对泄洪冲沙闸底板进行全面的固结灌浆处理,施工过程中采用自上而下分段灌浆方法,对现有的钻探与灌浆工艺技术进行优化组合,最终经灌后质量检查,结果满足深厚砂砾石覆盖层固结灌浆的设计要求,取得了良好的效果。更多还原     

南水北调邢台市区段石渠模筑衬砌试验研究

石渠衬砌施工为南水北调渠道衬砌施工的重要项目,如何保证施工质量,加快施工进度成为石渠衬砌施工之前的重要试验内容。本文通过对南水北调中线邢台市区段石渠模筑衬砌试验进行分析总结,得到了一些具体的施工方法及施工参数,对后续石渠衬砌施工提供重要数据支撑。     

黄河沙芯复合结构备防石技术优势和经济分析

针对黄河防汛抢险中采用传统备防石存在的问题,研制了黄河沙芯钢筋混凝土复合结构备防石。利用复合材料的基本原理,采用钢筋混凝土和叠层复合材料的方法,对其生产工艺进行研究,并分析其经济效益和实施可行性。结果表明:该项目经济效益良好,按年产量50万m3、项目投资500万元计,产品直接经济效益为1 646.5万元/年。该产品降低了备防石使用成本,提高了性能,可作为天然石材备防石的代用品,同时有利于黄河泥沙综合治理。     

Recovering phosphorus as struvite from the digested swine wastewater with bittern as a magnesium source

Recovering nitrogen and phosphorus through struvite (MgNH4PO4 6H2O) crystallization from swine wastewater has gained increasing interest. However, swine wastewater contains complex compositions, which may hinder the formation of struvite crystal and affect the purity of the precipitates by forming other insoluble minerals. In this work, experiments were carried out to evaluate struvite precipitation in the anaerobically digested swine wastewater, with dosing bittern as a low-cost magnesium source. Exceeded 90% phosphate removal and 23-29% ammonium reduction were obtained. FTIR, XRD and mass balance analysis were combined to analyze the species of precipitated minerals. Results showed that the precipitates were struvite, mixed with amorphous calcium phosphate (ACP) and brucite. The presence of Ca2+ diminished the percentage of struvite and gave rise to ACP formation. Controlling pH below 9.5 and bittern dosage above 1% (w/w) could inhibit ACP precipitation and harvest a highly pure struvite crystal product.     

A study of NH3-N and P refixation by struvite formation in hybrid anaerobic reactor.

This research is concerned with the removal of ammonia nitrogen and phosphorus in foodwaste by crystallization. Reductions have been achieved by struvite formation after the addition of magnesium ions (Mg2+). Magnesium ions used in this study were from magnesium salts of MgCl2. The results of our analysis using scanning electron microscopy and energy dispersive X-ray analysis showed that the amount of struvite in precipitated sludge grew enough to be seen with the naked eye (600-700 microm). EDX analysis also showed that the main components of the struvite were magnesium and phosphorus. NH3-N removal efficiency using MgCl2 was 67% while PO4-P removal efficiency was 73%. It was confirmed that nitrogen and phosphorus could be stabilized and removal simultaneously through anaerobic digestion by Mg, NH3 and PO4-P, which were necessary for struvite formation.     

Predicting struvite formation for phosphorus recovery from human urine using an equilibrium model.

Interest in phosphorus recovery from urine diverted from faeces has been growing recently. Phosphorus in urine can be precipitated out as struvite (MgNH4PO4 x 6H2O) with addition of magnesium salt under alkaline conditions. Struvite formation, however, should be more well understood for its practical application. We predicted the struvite formation with a development of a new equilibrium model. The model considered the formation of eight different kinds of precipitates, including struvite, with effects of ionic strength and temperature. In addition, experiments on struvite formation in urine were conducted for the model validation. The model prediction of struvite formation had good agreement with the experimental results. The optimum pH to form struvite was predicted to be 9.4-9.7. In order to precipitate 99% of phosphate in urine with 1.5 fold Mg concentration to PO4-P, the pH value was necessary to be more than 8.1 based on the model prediction.     

Solutions to a combined problem of excessive hydrogen sulfide in biogas and struvite scaling.

The Woodman Point Wastewater Treatment Plant (WWTP) in Western Australia has experienced two separate problems causing avoidable maintenance costs: the build-up of massive struvite (MgNH4PO4. 6H2O) scaling downstream of the anaerobic digester and the formation of hydrogen sulfide (H2S) levels in the digester gas to levels that compromised gas engine operation and caused high operating costs on the gas scrubber. As both problems hang together with a chemical imbalance in the anaerobic digester, we decided to investigate whether both problems could be (feasibly and economically) addressed by a common solution (such as dosing of iron solutions to precipitate both sulfide and phosphate), or by using separate approaches. Laboratory results showed that, the hydrogen sulfide emission in digesters could be effectively and economically controlled by the addition of iron dosing. Slightly higher than the theoretical value of 1.5 mol of FeCl3 was required to precipitate 1 mol of dissolved sulfide inside the digester. Due to the high concentration of PO4(3-) in the digested sludge liquor, significantly higher iron is required for struvite precipitation. Iron dosing did not appear an economic solution for struvite control via iron phosphate formation. By taking advantage of the natural tendency of struvite formation in the digester liquid, it is possible to reduce the risk of struvite precipitation in and around the sludge-dewatering centrifuge by increasing the pH to precipitate struvite out before passing through the centrifuge. However, as the Mg2+/PO4(3-) molar ratio in digested sludge was low, by increasing the pH alone (using NaOH) the precipitation of PO4(3-) was limited by the amount of cations (Ca2+ and Mg2+) available in the sludge. Although this would reduce struvite precipitation in the centrifuge, it could not significantly reduce PO4(3-) recycling back to the plant. For long-term operation, maximum PO4(3-) reduction should be the ultimate aim to minimise PO4(3-) accumulation in the plant. Magnesium hydroxide liquid (MHL) was found to be the most cost-effective chemical to achieve this goal. It enhanced struvite precipitation from both, digested sludge and centrate to the point where more than 95% PO4(3-) reduction in the digested sludge was achieved.     

Occurrence of micro-organic pollutants on phosphorus recovery from urine

Increased population growth and food prices have resulted in more demand for fertilizers, especially phosphorus (P), to be used in agriculture and production of food crops. Phosphorus is one of the important natural resources and will be exhausted in the near future. Nowadays, struvite production is a good method to recover P from urine. However, the natural urines contain high amounts of micro-organic pollutants which may cause health risks. Therefore, in this contribution, we investigated the amount of micro-organic pollutants in struvite from urine. There are various kinds of pharmaceuticals and hormones which are used in the world. Nevertheless, we focused on 10 pharmaceuticals (amoxycillin, carbamazepine, erythromycin, furosemide, atenolol, ibuprofen, norfloxacin, trimethoprim, tetracycline, and acetylsalicylic acid) and one hormone (17β-estradiol) as representatives. The experiments were carried out with synthetic and natural urines. After the production of struvite, the results from synthetic and natural urine samples showed that only tetracycline, erythromycin, and norfloxacin remained in the struvite, and, especially, tetracycline remained in struvite with quite a high amount.     

Removal of ammonium from aqueous solutions using the residue obtained from struvite pyrogenation

This paper reports the results of laboratory studies on the removal of ammonium from aqueous solutions using struvite pyrogenation residues. A series of experiments were conducted to examine the effects of the pyrogenation temperature (90-210 °C) and time (0.5-4 h) on the ammonium release of struvite. In addition, the pyrolysate of struvite produced at different pyrogenation temperatures and times was recycled for ammonium removal from aqueous solutions. The experimental results indicated that the ammonium release ratio of struvite increased with an increase in the pyrogenation temperature and time, and the struvite pyrolysate used as magnesium and phosphate source for ammonium removal was produced at the optimal condition of pyrogenation temperature of 150 °C for 1 h. Furthermore, experimental results showed that the optimum pH and pyrolysate dosage for ammonium removal from 100 ml synthetic wastewater (1,350 mg ammonium/L) were at pH 9 and 2.4 g of struvite pyrolysate, respectively, and initial ammonium concentration played a significant role in the ammonium removal by the struvite pyrolysate. In order to further reduce the cost of struvite precipitation, the struvite pyrolysate was repeatedly used for four cycles. The results of economic analysis showed that recycling struvite for three process cycles should be reasonable for ammonium removal, with ammonium removal efficiencies of over 50% and a reduction of 40% in the removal cost per kg NH(4)(+).     

Phosphorus recovery as struvite from eutropic waters by XDA-7 resin

Phosphorus releases into aquatic environment and its subsequent contribution to eutrophication have resulted in a widespread global pollution issue. However, phosphorus is a non-renewable source. The potential supplies of phosphorus are decreasing worldwide. Therefore, removal and recovery of phosphorus from the eutropic waters is important, emergent and necessary. In this research, experiments for recovering phosphate from eutropic waters by anion exchange combined with struvite precipitation were conducted. The results indicated that the prepared XDA-7 resin was an effective adsorbent for phosphate. The adsorption isotherm of XDA-7 resin was found to be a modified Freundlich type. The maximum phosphate adsorption (20.9 mg/g) occurred in the pH range of 6.0-8.0. Phosphate adsorbed on the XDA-7 resin was effectively desorbed with 8% NaCl solution, and the resin was able to be regenerated with 3% NaClO and 4% NaOH solutions. Phosphate desorbed from the resin was recovered as magnesium ammonium phosphate (struvite). The obtained struvite was analyzed by acid dissolution method, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The struvite precipitate was found to be 75.8% in purity, a high-value fertilizer.     

Ammonium nitrogen removal from slurry-type swine wastewater by pretreatment using struvite crystallization for nitrogen control of anaerobic digestion.

Precipitation of ammonium together with phosphate and magnesium is a possible alternative for lowering the nitrogen content of wastewater. In this study we examine the removal of ammonium nitrogen and phosphorus from slurry-type swine wastewater containing high concentrations of nutrients by the addition of phosphoric acid along with either calcium oxide or magnesium oxide, which leads to the crystallization of insoluble salts such as hydroxyapatite and struvite. The struvite crystallization method showed a high capacity for the removal of nitrogen when magnesium oxide and phosphoric acid were used as the magnesium and phosphate sources, respectively. When it was applied to swine wastewater containing a high concentration of nitrogen, the injection molar ratio of Mg2+:NH4+:PO4(3-) that gave maximum ammonium nitrogen removal was 3.0:1.0:1.5.     

Application of a fuzzy algorithm for pH control in a struvite crystallisation reactor.

A struvite crystallisation process is highly dependent on pH. To achieve a high phosphorus recovery as struvite it is important to have an accurate control of pH in the reactor. The high non-linear response of pH value makes manual pH control difficult. Therefore, a software based on fuzzy logic control (FLC) has been developed to maintain the pH at a set value in a stirred reactor to crystallise struvite. The FLC developed has been based on Larsen's inference. In order to confirm the improvement of the pH stability using FLC software, different experiments have been carried out with manual control of the pH value, and with the FLC software. It has been demonstrated that using FLC software allows a precise control of pH with high stability, optimises the process, and minimises the operator intervention.     

Effects of various process parameters on struvite precipitation kinetics and subsequent determination of rate constants.

In this paper, struvite (MgNH(4)PO(4).6H(2)O) precipitation kinetics were studied with different operating conditions (varying supersaturation, pH, Mg:P ratio, degree of mixing and seeding conditions) and relevant rate constants were determined by fitting a slightly modified first-order kinetic model to the experimental data obtained. The rate of change of ortho-P concentration in the bulk solutions increases with increasing supersaturation ratio. The estimated rate constants are 2.034, 1.716 and 0.690 hr(-1) for the supersaturation ratio of 9.64, 4.83, and 2.44, respectively. Kinetic parameters were also evaluated for the Mg:P ratio between the ranges of 1.0 and 1.6, indicating higher phosphorus removal efficiency with increasing Mg:P ratio. The rate constants were found to be 0.942, 2.034 and 2.712 hr(-1) for Mg:P ratios of 1.0, 1.3 and 1.6, respectively. The experimental observations for kinetic study of struvite precipitation with different stirrer speeds clearly show that the mixing intensity used had little effect on the intrinsic rate constants. K values found to be 2.034 and 1.902 h(-1) for 100 and 70 rpm, respectively. Seeding, with 250-500 microm of seed crystals during the struvite precipitation kinetics test, was found to have very little effect on the ortho-P removal.