ph and Mg/Ca control for biological treatment of an offensive flavour (2-MIB)

From a series of experimental observations, it was found that removal rates of the offensive flavor 2-methylisoborneol(2-MIB) and ammonia by a biological treatment for water supply were rather unstable and that the removal rates of them often became reverse such as low removal in 2-MIB and high removal of ammonia. One reason for the reverse phenomenon was found that the affinities of sludge around bacteria with 2-MIB and ammonia often became reversed. The affinities of sludge with 2-MIB and ammonia were found to be changeable depending upon pH along with magnesium (Mg) and calcium (Ca) concentrations in sludge. From these findings, control of pH and magnesium calcium ratio (Mg/Ca) of raw water was recommended for simultaneous and stable removal of 2-MIB and ammonia. From plant scale experiments equipped with automatic pH controller, the effects of pH and Mg/Ca control for biological treatment of 2-MIB and ammonia were observed in a biological activated filtration. Here, a biological activated carbon filtration means a longer filtration than 40 to 50 days from the beginning. The obtained results were almost as expected, showing high removal rates of both 2-MIB and ammonia.     

Semi-intensive treatment plants for wastewater reuse in irrigation.

Semi-intensive technologies are a middle term between intensive ones (e.g., activated sludge with a retention time of hours) and extensive ones (e.g., stabilization ponds with a retention time of several weeks). The most common semi-intensive configuration used in Israel is made of anaerobic ponds followed by aerated lagoons. These small low-energy units remove about 75-80% of the BOD and are followed by wastewater reservoirs for storage and complementary treatment. The reduction in loading allows a flexible operation of the reservoirs for the removal of other pollutants, while providing storage capacity to cope with the changes in water demand for irrigation during the year. In schemes for wastewater reuse in irrigation, this lay-out has proved to be low-cost, low-energy, flexible, reliable and efficient. Variations of this basic configuration are the use of UASB reactors instead of anaerobic ponds, aerated lagoons in series or low-rate trickling filters instead of aerated lagoons, constructed wetlands or rock-filters for algae removal, etc. Semi-intensive technologies use less energy than intensive ones, and less land than extensive ones. They can remove as much BOD as intensive ones, and as much pathogens and refractory pollutants as extensive ones. They release no or very small amounts of sludge.     

Experimental study on nitrification in a submerged aerated biofilter.

The aim of the present work was to evaluate the performance of a semi-pilot scale BAF in order to obtain a highly polished effluent in terms of removal of organic matter, suspended solids and ammonia and to observe the influence of temperature, pH and nitrite accumulation on the nitrification process. The ammonia removal efficiency during summer and winter and the nitrite accumulation in presence of free ammonia were observed. The biomass density was measured at different filter bed heights and the sludge production from the effluent of the backwashing water was evaluated. The results obtained were used to calibrate a mathematical model for the prediction of the ammonia removal profile in the filter bed and of biomass thickness.     

好氧硝化污泥启动厌氧氨氧化试验研究

以好氧硝化污泥为培养污泥,采用经稀释的猪场废水启动厌氧氨氧化反应器,经过125 d的培养,根据ASBR反应器出水水样监测结果显示:ASBR反应器稳定运行后NH4+-N、NO2--N的去除率分别达到91.7%、92.0%,说明采用ASBR反应器,接种好氧硝化污泥可成功启动厌氧氨氧化反应器,验证了利用厌氧氨氧化工艺处理类似养殖废水的高氨氮废水的可能性.     

沸石去除地下水源水中氨氮的试验研究

地下水源水中氨氮的去除有其特殊性,研究利用沸石直接过滤氨氮超标地下水,并对沸石去除氨氮的机理进行了探讨。试验结果表明,滤速和进水氨氮浓度对沸石柱运行效果有很大影响,沸石对低浓度氨氮具有良好的去除作用。在滤速为6m/h,进水氨氮浓度分别为0.8mg/L和1.42mg/L时,以《城市供水水质标准》(CJ/T 206—2005)规定的0.5mg/L为出水水质标准,沸石柱可以分别运行65h和18h。沸石柱对氨氮的去除是吸附和离子交换共同作用的结果。     

Anaerobic digestion of slaughterhouse waste with UF-membrane separation and recycling of permeate after free ammonia stripping.

Anaerobic digestion can adapt to free ammonia to a certain extent. During the anaerobic digestion of slaughterhouse waste, however, an ammonia concentration of up to 15 g Nl(-1) can be reached in the sludge liquid and this will even inhibit adapted sludge. To lower this concentration, a fraction of the digester liquid must therefore be continuously separated from the digested sludge and the free ammonia stripped before the liquid is recycled to the digester. A mesophilic laboratory digester was successfully operated with an ammonium concentration of 4-5g l(-1) and a pH of 8.0-8.4. After free ammonia stripping, the excess liquid was treated in a laboratory SBR for nitrogen and phosphorus removal before being added to the receiving water. The effluent had no toxic effect on daphnia and algae.     

污泥碱解发酵液用于生活污水脱氮 除磷的效果研究

为了减轻水体富营养化程度,提高污水的脱氮除磷效果,并解决污泥减量化和资源化问题,本研究将碱预处理的污泥进行厌氧发酵产酸,并将发酵液作为污水脱氮除磷的外加碳源。研究结果表明：投加污泥发酵液后,出水氨氮浓度为0.3~0.5 mg/L,总磷浓度为0.5 mg/L,与未投加污泥发酵液相比分别降低了1.7~2.3 mg/L和3~4 mg/L。     

The application of model predictive control of ammonia nitrogen in an activated sludge process

In this paper a model predictive controller (MPC) for ammonia nitrogen is presented and evaluated in a real activated sludge process. A reduced nonlinear mathematical model based on mass balances is used to model the ammonia nitrogen in the activated sludge plant. An MPC algorithm that minimises only the control error at the end of the prediction interval is applied. The results of the ammonia MPC were compared with the results of the ammonia feedforward-PI and ammonia PI controllers from our previous study. The ammonia MPC and ammonia feedforward-PI controller give better results in terms of ammonia removal and aeration energy consumption than the ammonia PI controller because of the measurable disturbances used. On the other hand, with the ammonia MPC, comparable or even slightly poorer results than with the ammonia feedforward-PI controller are obtained. Further improvements to the MPC could be possible with an improved accuracy of the nonlinear reduced model of the ammonia nitrogen, more sophisticated control criteria used inside the controller and the extension of the problem from univariable ammonia to multivariable total nitrogen control.     

Water quality management in the Ruhr area

The Ruhr River is the major source of water supply for the North Rhine-Westphalian industrial district. To ensure drinking water supply from the river a system of reservoirs has been constructed for low flow augmentation. Five additional river impoundments have been built for the abatement of nonpoint pollution. The Ruhr River Association was established in 1913. Its first task was the reduction of coarse pollution by mechanical treatment plants. Activated sludge plants were introduced as early as 1926. Developments continued and presently tertiary treatment is performed by polishing lagoons on one-third of the Ruhrverband plants and a programme of storage and subsequent biological treatment of stormwater is underway. One important future task is nutrient removal from municipal wastewater by chemical precipitation and biological processes. Phosphorous concentrations in river water have to be diminished to fight eutrophication while nitrogen must be reduced because of drinking water considerations. Heavy metals have to be further controlled and organically attached halogens have to be diminished.     

Nitrogen removal in maturation ponds: tracer experiments with 15N-labelled ammonia.

A primary maturation pond (M1) was spiked with labelled ammonium chloride (15NH4Cl) to track ammonium transformations associated with algal uptake and subsequent sedimentation. Conventional sampling based on grab samples collected from M1 influent, water column and effluent, and processed for unfiltered and filtered TKN, ammonium, nitrite and nitrate, found low total nitrogen removal (8%) and high ammonium nitrogen removal (90%). Stable isotope analysis of 15N from suspended organic and ammonium nitrogen fractions in M1 effluent revealed that labelled ammonium was mainly found in the organic fraction (69% of the 15N recovered), rather than the inorganic fraction (5%). Algal uptake was the predominant pathway for ammonia removal, even though conditions were favourable for ammonia volatilization (8.9 < pH <10.1 units, 15.2 < temperature <18.8 degrees C). Total nitrogen was removed by ammonia volatilization at 15 g N/ha d (3%), organic nitrogen sedimentation at 105 g N/ha d (20%), and in-pond accumulation due to algal uptake at 377 g N/ha d (71%). Algal uptake of ammonium and subsequent sedimentation and retention in the benthic sludge, after partial ammonification of the algal organic nitrogen, is thus likely to be the dominant mechanism for permanent nitrogen removal in maturation ponds during warm summer months in England.     

Some observations on the effects of accumulated benthic sludge on the behaviour of waste stabilisation ponds.

The effect of accumulated bottom sludge on water column characteristics was studied in two pilot-scale ponds. Parameters measured were ammonia, nitrate, phosphate, COD, suspended solids, dissolved oxygen (DO), temperature and light intensity. The de-sludged pond showed a stronger correlation between DO, light intensity, nutrients and suspended solids with the controlling factor being availability of nitrogen. This was less apparent in the pond with sludge where nutrient levels were higher and more complex mechanisms controlled biomass concentration. Water column characteristics in the two ponds converged rapidly in 7-10 weeks, however, due to accumulation of fresh sludge.     

Implementing biofilm carriers into activated sludge process — 15 years of experience

Seven full-scale hybrid systems have been operating in waste water treatment plants in Southern Germany since the early eighties. The aerobic submerged biofilm technology applied is known as Bio-2-Sludge process. The plants have originally been designed for carbon removal and were modified later on to allow nitrogen removal. For this purpose, the age of the operating sludge had to be raised. This was achieved without any addition of reactor volume by installation of submerged biofilm carriers. The use of the submerged, fixed bed devices results in a very efficient sludge, allowing MLSS of up to 11 g/l. Operational results show both a purification improvement of BOD and ammonia and the existence of simultaneous denitrification. Practical experiences of long-term operations are being reported.     

高铁锰氨氮伴生地下水生物深度净化的工程实践

对高铁锰氨氮伴生的地下水采用传统接触氧化工艺处理时,水厂滤池出水锰严重超标,经模拟滤柱试验发现,滤层结构和溶解氧不足是高浓度Fe~(2+)、Mn~(2+)、NH_3—N同池生物净化失败的原因。根据滤柱试验结果,提出了强化曝气溶氧,无烟煤锰砂双层滤料一级生物过滤的工艺流程,实现了寒区高铁锰氨氮伴生的潜流地下水的同池深度净化。并用研究成果改造了哈尔滨市松北区前进水厂一期净水系统。出厂水总铁小于0.2 mg/L,锰小于0.05 mg/L,氨氮小于0.2 mg/L,满足国标要求,且长期高效、稳定运行,由此,创建了寒区高铁锰氨氮伴生地下水生物深度净化示范工程。     

Combined wastewater feed directly into final clarification - advantage for receiving rivers

With a view to a reduction of the discharge from combined water outflow, the increase of the influent to a wastewater treatment plant can be an efficient solution, for cases in which the discharge concentration of the wastewater treatment plant would not deteriorate significantly as a result. Through bypassing the aeration with combined water and a direct feed of the combined water into the final clarification (Mina-Process) the specific sludge volume loading, which is significant to the efficiency of the final clarification, will not be raised. But the adsorption capability of the aerated sludge, the sedimentation effect of the final clarification, and the partial recirculation over return-sludge can be used for an elimination of suspended solids, chemical oxygen demand (COD), ammonia and phosphate from the combined wastewater. In large-scale tests in Wilhelmshaven (160,000 PE), removal efficiencies for the elimination in the bypass of 75% of COD, 60% of ammonia and 89% of suspended solids were reached. In comparison with conventional procedures for combined water treatment (e.g. storage volumes, soil filter) the Mina-Process has the possibility to achieve a highly efficient and economical combined water treatment by using the capability of existing clarifiers.     

Biological treatment of sludge digester liquids.

Nitrogen removal in side stream processes offers a good potential for upgrading wastewater treatment plants (WWTPs) that need to meet stricter effluent standards. Removing nutrients from these internal process flows significantly reduces the N-load to the main treatment plant. These internal flows mainly result from the sludge processing and have a high temperature and a high concentration of ammonia. Therefore, the required reactor volumes as well as the required aerobic SRT are small. Generally, biological treatment processes are more economical and preferred over physical-chemical processes. Recently, several biological treatment processes have been introduced for sludge water treatment. These processes are available now on the activated sludge market (e.g. SHARON, ANAMMOX and BABE processes). The technologies differ in concept and in the limitations guiding the application of these processes for upgrading WWTPs. This paper reviews and compares different biological alternatives for nitrogen removal in side streams. The limitations for selecting a technology from the available ones in the activated sludge market are noted and analysed. It is stressed that the choice for a certain process is based on more aspects than pure process engineering arguments.     

Winery and distillery wastewater treatment by anaerobic digestion.

Anaerobic digestion is widely used for wastewater treatment, especially in the food industries. Generally after the anaerobic treatment there is an aerobic post-treatment in order to return the treated water to nature. Several technologies are applied for winery wastewater treatment. They are using free cells or flocs (anaerobic contact digesters, anaerobic sequencing batch reactors and anaerobic lagoons), anaerobic granules (Upflow Anaerobic Sludge Blanket--UASB), or biofilms on fixed support (anaerobic filter) or on mobile support as with the fluidised bed. Some technologies include two strategies, e.g. a sludge bed with anaerobic filter as in the hybrid digester. With winery wastewaters (as for vinasses from distilleries) the removal yield for anaerobic digestion is very high, up to 90-95% COD removal. The organic loads are between 5 and 15 kgCOD/m3 of digester/day. The biogas production is between 400 and 600 L per kg COD removed with 60 to 70% methane content. For anaerobic and aerobic post-treatment of vinasses in the Cognac region, REVICO company has 99.7% COD removal and the cost is 0.52 Euro/m3 of vinasses.     

Rapid start-up of a nitrifying reactor using aerobic granular sludge as seed sludge

In this study, the effectiveness of aerobic granular sludge as seed sludge for rapid start-up of nitrifying processes was investigated using a laboratory-scale continuous stirred-tank reactor (CSTR) fed with completely inorganic wastewater which contained a high concentration of ammonia. Even when a large amount of granular biomass was inoculated in the reactor, and the characteristics of influent wastewater were abruptly changed, excess biomass washout was not observed, and biomass concentration was kept high at the start-up period due to high settling ability of the aerobic granular sludge. As a result, an ammonia removal rate immediately increased and reached more than 1.0 kg N/m(3)/d within 20 days and up to 1.8 kg N/m(3)/d on day 39. Subsequently, high rate nitritation was stably attained during 100 days. However, nitrite accumulation had been observed for 140 days before attaining complete nitrification to nitrate. Fluorescence in situ hybridization analysis revealed the increase in amount of ammonia-oxidizing bacteria which existed in the outer edge of the granular sludge during the start-up period. This microbial ecological change would make it possible to attain high rate ammonia removal.     

Development and implementation of a robust deammonification process.

Deammonification represents a short-cut in the N-metabolism pathway and comprises 2 steps: about half the amount of ammonia is oxidised to nitrite and then residual ammonia and nitrite is anaerobically transformed to elementary nitrogen. Implementation of the pH-controlled DEMON process for deammonification of reject water in a single-sludge SBR system at the WWTP Strass (Austria) contributed essentially to energy self-sufficiency of the plant. The specific energy demand of the side-stream process equals 1.16 kWh per kg ammonia nitrogen removed comparing to about 6.5 kWh of mainstream treatment. Has this resource saving technology already approached state of the art? Deammonification has been operated in full-scale now for almost 3 years without interruption reaching annual ammonia removal rates beyond 90%. Biomass enrichment and DEMON-start-up in Strass took a period of 2.5 years whereas start-up period at the WWTP Glarnerland (Switzerland) was reduced to 50 days due to transfer of substantial amounts of seed sludge.     

Evaluation of sludge reduction and phosphorus recovery efficiencies in a new advanced wastewater treatment system using denitrifying polyphosphate accumulating organisms.

A new biological nutrient removal process, anaerobic-oxic-anoxic (A/O/A) system using denitrifying polyphosphate-accumulating organisms (DNPAOs), was proposed. To attain excess sludge reduction and phosphorus recovery, the A/O/A system equipped with ozonation tank and phosphorus adsorption column was operated for 92 days, and water quality of the effluent, sludge reduction efficiency, and phosphorus recovery efficiency were evaluated. As a result, TOC, T-N and T-P removal efficiency were 85%, 70% and 85%, respectively, throughout the operating period. These slightly lower removal efficiencies than conventional anaerobic-anoxic-oxic (A/A/O) processes were due to the unexpected microbial population in this system where DNPAOs were not the dominant group but normal polyphosphate-accumulating organisms (PAOs) that could not utilize nitrate and nitrite as electron acceptor became dominant. However, it was successfully demonstrated that 34-127% of sludge reduction and around 80% of phosphorus recovery were attained. In conclusion, the A/O/A system equipped with ozonation and phosphorus adsorption systems is useful as a new advanced wastewater treatment plant (WWTP) to resolve the problems of increasing excess sludge and depleted phosphorus.     

Hydrology and Nutrient Enrichment at Two Coastal Lagoon Systems in Northern Greece

The lagoons of N.E. Greece, located on the western side of NestosRiver, and of N.W. Greece, located at the lower reaches of Kalamas River, are among the most important shallow, semi-enclosed ecosystems in Northern Greece. The temporal variability of nutrients at both lagoonal systems shows the strong influence of fresh water discharge on water quality. Nutrient enrichment factors showed that nitrites and ammonium were six times higher at the lagoons of N.W. Greece than those observed at N.E. Greece, while phosphates were forty times higherat Nestos River lagoons. The flushing half-life was calculatedbased on a combination of hydrological and tidal processes, foreach lagoon of these two systems, allowing for the assessment ofwater quality changes. Proper management measures for both systems should focus on the control of fresh water quality entering the lagoons, the reduction of phosphoric fertilizers used by agriculture and the better oxygenation of the water column. One way to eliminate massive fish deaths during the winter in N.E. Greece is also the transfer of fresh, warm groundwater, while bathymetric modifications and channel wideningare needed at the lagoons of N.W. Greece.