Effect of settling on performance of the upflow anaerobic sludge bed reactors

The effects of settler volume on the start-up and steady-state performance of 41. laboratory upflow sludge bed reactors treating bean blanching waste of 10,000 mg COD l⁻¹ were determined. The rate of start-up, as well as the maximum loading rate, increased with increased settler volume and performance. A loading rate of 30 kg COD m⁻³ day⁻¹ (based on reactor volume alone) and a COD removal of 95% was obtained with a 21. settling flask and a 4 to 1 recirculation rate. Without a settler, the maximum loading rate was 10 kg COD m⁻³ day⁻¹. The sludge was flocculent rather than granular. Sludge profiles and characteristics in the reactors and settlers were determined.     

Anaerobic treatment of domestic sewage with a rotating stationary fixed-film reactor

An anaerobic reactor was developed for on-site and small scale wastewater treatment applications. The up-flow fixed-film reactor was packed with two different types of circular media: stationary and rotating. Experimental results showed the reactor can treat primary settled domestic wastewaters efficiently, under different operating conditions. At 29°C the mixing action did not improve the organic matter removal efficiencies (65% COD removal was obtained with an organic load of 1.7 kg COD m⁻³ day⁻¹ and a 6 h space time). However, at 16°C the removal efficiency was greatly dependent on the mixing conditions: a gentle agitation (5 rpm) up-graded significantly the reactor operation, but no improvement was observed beyond 15 rpm. It appears that at low temperatures liquid biofilm mass transfer is the rate limiting step when treating sewage anaerobically. Gas production was rather limited [0.11 m³ (STP) kg⁻¹ COD removed] and calculations suggest that more than 50% of the total CH₄ produced is lost due to its dissolution in the effluent. Improved effluent quality, reduced sludge production (0.11 kg TSS kg⁻¹ COD supplied), low energy requirements and low maintenance needs make this reactor a good, compact alternative to conventional household wastewater treatment processes.     

Estimation of film accumulation in percolating filters: Comparison of methods

Estimation of film accumulation is necessary for the successful operational management of percolating filters. Prevention of ponding and loss of performance due to excessive film accumulation, and the optimization of the recirculation and alternating double filtration processes can only be achieved by regular monitoring of film growth. Five methods of determining film accumulation are compared; total film weight, total dry solids, volatile solids, percentage settlement of solids and the neutron scattering technique. The methods were used to monitor the film growth in pilot filters containing a mineral and a random plastics medium, over two twelve-month loading periods at 1.68 m³ m⁻³ day⁻¹ (0.28 kg BOD m⁻³ day⁻¹) and 3.37 m³ m⁻³ day⁻¹ (0.63 kg BOD m⁻³ day⁻¹).

Good correlations (P < 0.001) are found between all methods at the lower loading although the neutron scattering results are not significantly correlated (P > 0.10) with any of the gravimetric methods at the higher loading. Although the neutron scattering technique does provide a rapid and sensitive measure of hydrogen atoms in the filter, the results, expressed as percentage saturation of the voids, are not directly transferable to film weights and should be treated separately and not as a true measure of film accumulation.     

Denitrification studies with glycerol as a carbon source

Based on the results of experimental work, the use of glycerol as a carbon source for denitrification is discussed. Investigations were carried out in modified UASB reactor using a mixed bacterial population in medium containing 600 mg NO₃---N and essential biogens. It was found that at the most favourable C:N RATIO = 1.0 the efficiency of denitrification depended on nitrate load as well as on cell residence time. At nitrate loads in the range 220–670 mg NO₃---Nl⁻¹ day⁻¹ (0.08–0.14 mg NO₃---N mg⁻¹ day⁻¹) nitrogen removal was 0.6–0.12 mg N mg⁻¹ day⁻¹, respectively. Denitrification unit biocenosis was composed of bacteria, fungi and protozoa. The number of denitrifying bacteria per sludge weight unit within the studied range of nitrate loads was constant and averaged 23 × 10⁷ cells mg⁻¹.     

Seasonal variation of phosphorus release from the sediments of Shallow Lake Balaton (Hungary)

Phosphorus release was low from intact sediment cores of the mesotrophic area of the lake throughout the year, and amounted to 0.3 mg P m⁻² day⁻¹ during autumn in short-term incubations. In the hypertrophic area maximum release (2.8 mg Pm⁻² day⁻¹) was measured during summer.

Phosphorus release showed a rapid increase from long-term incubated intact sediment cores with the increasing pH of the overlying water. At the ecologically real maximum pH the release may amount to 0.8 and 4.0 mg P m⁻² day⁻¹ in the mesotrophic and hypertrophic areas, respectively. A release of 2.0–3.9 mg P m⁻² day⁻¹ was estimated from sediment suspensions of the hypertrophic area within a pH range of 8–9. These values are similar to the external phosphorus loadings of the respective areas.

The most important phosphorus mobilizing factors are pH and the decomposition of the organic matter in the sediments. Redox conditions may play a significant indirect role in the regulation of the internal loading.

A positive feedback is hypothesized between the internal phosphorus loading and primary production both processes being affected by the external loading in different ways.     

云南某废弃菜叶处理厂废水处理工程实例

废弃菜叶处理(破碎+厌氧产沼气)过程中产生的废水是一种污染物浓度较高、C/N偏低的废水。云南某废弃菜叶处理厂废水处理工程采用A²O²(二级O池为MBR膜池)工艺,以强化氮的脱除,保证出水TN的达标。对A²O²工艺的启动特性、运行效果及运行费用组成进行了分析。在工艺启动过程中,COD的去除效率可以稳定在70%以上;当硝化反应发生后,对NH₄⁺-N的去除率>99.5%;投加一定量的碳源后,对TN可以达到较高的去除率。稳定运行后,出水的COD、NH₄⁺-N、TN和TP分别稳定在300、10、45、5 mg/L以下,满足《污水排入城镇下水道水质标准》(GB/T 31962—2015)的C级标准。经测算,处理成本为27.564元/m³。     

Kinetics of alachlor transformation and identification of metabolites under anaerobic conditions

Alachlor is one of the two most commonly used herbicides in the United States. In the environment, little mineralization of this compound has been found to occur, and metabolites of alachlor may be formed and could accumulate. The objectives of this study were to determine the rate of alachlor biotransformation and to identify the transformation intermediates formed under aqueous denitrifying, methanogenic, and sulfate-reducing conditions. Second-order biotrasnformation coefficients for alachlor were determined to be 7.6 × 10⁻⁵ (±4.0 × 10⁻⁵), 2.9 × 10⁻³ (±1.6 × 10⁻³), and 1.5 × 10⁻² (±1.4 × 10⁻²) 1 mg VSS⁻¹ day⁻¹ under denitrifying, methanogenic, and sulfate-reducing conditions, respectively. Acetyl alachlor and diethyl aniline were positively identified as transformation products of alachlor under all conditions. In denitrifying reactors aniline was identified as a product of alachlor. When acetyl alachlor was fed as the parent compound, aniline was also identified as a transformation product under methanogenic conditions. This research showed that although alachlor is degraded under denitrifying, methanogenic, and sulfate-reducing conditions, significant concentrations of several metabolites are formed and are only slowly degraded.     

Anaerobic biological treatment of phenol at 9.5-15 degrees C in an expanded granular sludge bed (EGSB)-based bioreactor

The aims of this study were to demonstrate the (1) feasibility of psychrophilic, or low-temperature, anaerobic digestion (PAD) of phenolic wastewaters at 10–15 °C; (2) economic attractiveness of PAD for the treatment of phenol as measured by daily biogas yields and (3) impact on bioreactor performance of phenol loading rates (PLRs) in excess of those previously documented (1.2 kg phenol m⁻³ d⁻¹). Two expanded granular sludge bed (EGSB)-based bioreactors, R1 and R2, were employed to mineralise a volatile fatty acid-based wastewater. R2 influent wastewater was supplemented with phenol at an initial concentration of 500 mg l⁻¹ (PLR, 1 kg m⁻³ d⁻¹). Reactor performance was measured by chemical oxygen demand (COD) removal efficiency, CH₄ composition of biogas and phenol removal (R2 only). Specific methanogenic activity, biodegradability and toxicity assays were employed to monitor the physiological capacity of reactor biomass samples. The applied PLR was increased to 2 kg m⁻³ d⁻¹ on day 147 and phenol removal by day 415 was 99% efficient, with 4 mg l⁻¹ present in R2 effluent. The operational temperature of R1 (control) and R2 was reduced by stepwise decrements from 15 °C through to a final operating temperature of 9.5 °C. COD removal efficiencies of c. 90% were recorded in both bioreactors at the conclusion of the trial (day 673), when the phenol concentration in R2 effluent was below 30 mg l⁻¹. Daily biogas yields were determined during the final (9.5 °C) operating period, when typical daily R2 CH₄ yields of c. 3.3 l CH₄ g⁻¹ COD_removed d⁻¹ were recorded. The rate of phenol depletion and methanation by R2 biomass by day 673 were 68 mg phenol g VSS⁻¹ d⁻¹ and 12–20 ml CH₄ g VSS⁻¹ d⁻¹, respectively.     

Modelling nitrification effects on the dissolved oxygen regime of the speed river

Field studies on nitrification in an 11 km stretch of the Speed River below Guelph are described. The data, collected during three intensive surveys in spring-summer 1976 and winter 1977, were used to calibrate and verify a steady-state dissolved oxygen (DO) model which incorporates the effects of carbonaceous and nitrogenous oxygen demand (CBOD and NOD), plant and algal respiration and photosynthesis, and reaeration. The model calibration result for one of the survey conditions includes comparisons between the corresponding observed and predicted values of CBOD, NOD and daily minimum and maximum DO. The comparisons of the first three sets of parameters were satisfactory, but the predicted maximum DO values were generally higher than the observations. The model verification results for two other survey conditions were somewhat similar to those of the calibration study. Predictions of the relative effects of various sinks on the minimum DO levels under one of the survey conditions indicate that instream nitrification alone causes a DO deficit of about 4.5 mg 1⁻¹; in contrast, the deficits due to CBOD and respiration were in the order of 1 mg 1⁻¹ only. The model was also used to predict spatial DO distributions under several streamflow and temperature regimes. For each case, computer runs were made with NOD concentrations resulting from a conventional secondary (i.e. non-nitrified) efluent and a nitrified effluent. The predictions indicate that the minimum DO level increases with an increase in streamflow and a decrease in temperature. In the case of non-nitrified effluents, anoxic conditions are predicted to occur at about 25°C when streamflow rates are lower than about 1 m³s⁻¹; whereas in-plant nitrification would result in daily minimum DO levels of 4 mg 1⁻¹ or greater. The predictions also show the occurrence of two DO sags in the study stretch, one being mainly due to a high degree of nitrification, while the other is due to the combined effect of all of the DO sinks.     

节地型HBR生物膜技术在贵阳金百再生水厂的应用

贵阳金百再生水厂设计规模为3.0×10⁴m³/d,出水水质执行《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准,就近作为麦架河河道生态补水。生化处理采用节地型生物膜技术,通过悬浮填料和高填充率的固定床结构,实现生物膜处理和生物过滤的双重作用,高效去除污染物,省去二沉池,节省占地面积。介绍了该厂的工艺流程、构筑物设计及设备配置情况,并对运行效果进行总结。自运行以来,出水水质稳定达标,COD、SS、氨氮、总氮、总磷去除率分别为89.4%、92.8%、96.3%、48.4%、90.9%;节地效果明显,吨水占地仅为0.36 m²/(m³·d^-1);运行成本为0.56元/m³,与同等规模的传统活性污泥法污水厂的运行成本相近。     

Stabilized leachates: ozone-activated carbon treatment and kinetics

Ozone has been used as a pre-oxidation step for the treatment of stabilized leachates. Given the refractory nature of this type of effluents, the conversion of some wastewater quality parameters has been moderate after 1 h of ozonation (i.e. 30% chemical oxygen demand (COD) depletion). Ozone uptake was calculated in the interval 1.3–1.5 g of ozone per gram of COD degraded. An optimum dose of ozone has been experienced in terms of biodegradability of the processed effluent (60 min of treatment, 1×10⁻³ molL⁻¹ ozone inlet feeding concentration and 50 Lh⁻¹ gas flow-rate). pH and other typical hydroxyl radical generator systems exerted no influence on the efficiency of the process, suggesting the negligible role played by the indirect route of oxidation (generation of hydroxyl radicals). The ozonated effluent was thereafter treated in a second adsorption stage by using a commercial activated carbon. Removal levels up to 90% of COD in approximately 120 h were experienced for adsorbent dosages of 30 gL⁻¹. Both steps, the single ozonation and the adsorption stage have been modelled by using different pseudoempirical models.     

硫自养波形潜流人工湿地的脱氮机理及工况优化

将硫自养反硝化工艺与潜流人工湿地相结合,考察了其对低碳氮比污水中氮的去除效果。结果表明,增加曝气装置后硫自养波形潜流人工湿地的脱氮效果可以得到保障,在气水比为8∶1、水力负荷为0.8 m³/(m²·d)时,TN去除率为(70±5)%,出水TN浓度低于8 mg/L;NH4+-N去除率在90%以上,出水NH4+-N浓度低于3 mg/L;COD去除率为(50±2)%,出水COD浓度低于40 mg/L;p H值可维持在7~9。同时,石灰石填料具有同步除磷的效果。该工艺具有脱氮效率高、效果好、运行费用低的特点。     

Stream productivity analysis with dorm—III: Productivity of experimental streams

Thirty-two two-station diel dissolved oxygen surveys were made in the experimental streams of the U.S. EPA Monticello Ecological Research Station. The data were analyzed by a numerical Dissolved Oxygen Routing Model (DORM) to determine total community respiratory and photosynthetic rates. The artificial channels consisted of pools and riffles and had pH of 8.0, 6.3 and 5.4. Community photosynthetic production and respiration ranged from highs of 14.8 and 10.7gm⁻² day⁻¹ to lows of 1.5 and 2.6gm⁻² day⁻¹ between June and September 1979. P/R ratios varied from 2.1 in May to 0.6 in August. Seasonal trends were affected by pH and/or age of the channel. The channels also exhibited large diel variations in photosynthetic efficiency, where dependence of photosynthetic production upon light was nonlinear and had a strong hysteresis. This hysteresis cannot be explained by physical processes and is attributed to several biological processes.     

Productivity and nitrogen balance in large scale phytoplankton cultures

Biomass production and nitrogen balance was studied in 35,000 gal (133,000 1) phytoplankton cultures comprising the first stage in a tertiary sewage treatment-mariculture system. The diatom Phaeodactylum tricornutum persisted for most of the study. At secondary sewage effluent loadings sufficient to produce residual dissolved inorganic nitrogen concentrations above approximately 5 μg atoms l⁻¹, an N:C ratio (molar) of 0.17 was obtained and algal growth was not nutrient-limited. Biomass levels, and hence pond particulate carbon and nitrogen output, varied in response to solar irradiance and dilution rate, but not temperature. Mean winter and summer yields were approximately 1 and 5 g (83 and 417 mg atoms) C m⁻² d⁻¹ respectively. An inverse relationship existed between algal biomass concentration and dilution rate, such that in the late spring optimal pond yields occurred between 0.55 and 0.65 dilutions d⁻¹. Better than 95% dissolved total nitrogen removal was obtained. Net dissolved organic nitrogen production, that would offset dissolved inorganic nitrogen removal, did not occur. Pond particulate nitrogen output was usually less than dissolved total nitrogen removal. Probable explanations for this include (1) ammonia evolution to the atmosphere at high pond pH, (2) particulate nitrogen sedimentation, and (3) denitrification. Of these, the first is believed to be quantitatively the most significant.     

生物转盘在某城镇污水处理厂改造扩容工程中的应用

平凉市某污水处理厂原设计规模5.0×10⁴m³/d,采用传统A²/O+深度处理工艺,本次扩建后规模达到8.5×10⁴m³/d。针对厂区用地紧张、进水总氮浓度高等问题,缺氧区采用生物转盘强化系统的脱氮性能,好氧区改造为限氧曝气区,并新建初沉池以确保出水指标达标。实际运行数据显示,在低温、低碳氮比条件下,出水水质可稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A标准。该工程总投资为10793.17万元,直接运行成本为0.72元/m³。     

Upgrading a facultative pond by implanting water hyacinth

Water hyacinth was implanted in one of two existing facultative ponds and both units were operated in parallel under comparable conditions. The ponds were fed with mainly domestic wastewater after pretreatment in anaerobic ponds and operated at a BOD₅-loading of about 48 kg (ha d)⁻¹ and a detention time of 12 days. This paper covers a period of 4 months, from the implantation of the water hyacinths until no further systematic change in the treatment efficiency of the water hyacinth pond was observed. The median effluent concentrations of the facultative pond for SS, COD, TKN and TP were 55, 95, 6.4 and 1.4 mg l⁻¹, respectively. The values for the water hyacinth pond were 12, 26, 2.5 and 0.4 mg l⁻¹, respectively. The average DO effluent concentration of the water hyacinth pond was 1.2 mg l⁻¹, but this still increased slightly as compared to the influent. The study demonstrates that the implantation of water hyacinth is an appropriate option for upgrading facultative ponds. In many cases where more stringent effluent standards are imposed the method may be a suitable alternative to technical treatment processes.     

Manufacturing effects on the hydraulic properties of needlepunched nonwoven geotextiles

Needlepunched nonwoven geotextiles are entangled to form a complex three-dimensional structure by random fibers, accounting for its bulky nature, wide range of pore size distribution, and good drainage. With needlepunched nonwoven geotextiles, water can move in both the vertical and horizontal directions. This paper examines two types of needlepunched nonwovens: one produced from polyester staple fiber and the other made from polyester spunbond continuous filaments. Experimental results indicate that the permittivity of staple needlepunched nonwoven geotextiles varies from 1.77-4.51 s⁻¹; the permeability coefficient varies from 0.63-2.87 × 10⁻² m/s. The permittivity of spunbond needlepunched nonwoven geotextiles varies from 1.13-1.97 s⁻¹; the permeability coefficient varies from 0.48-1.09 × 10⁻² m/s. In addition, the transmissivity of needlepunched nonwoven geotextiles decrease to an essentially constant value as the normal stress is increases. The transmissivity of needlepunched nonwoven geotextiles examined varies from 155-2.75 × 10⁻⁶ m²/s over the normal stress range examined (5-200 kN/m²). The AOS value of 3 denier staple fiber needlepunched nonwovens is less than 0.074 mm, the AOS value of spunbonded 7 denier and, 15 d and 20 d needlepunched nonwovens are 0.21 mm, 0.25 mm and 0.30 mm, respectively.     

Utilisation de l''algue oocystis sp. pour le traitement tertiaire des eaux usées—I. Culture en vrac de cellules préalablement conditionnées en cyclostat

With the aim of developing an efficient and economic method for the tertiary treatment of wastewater, a two-phased culture system of Oocystis alga is presented. During the first phase, a unialgal strain grows in a cyclostat supplied with secondary effluents diluted to a low concentration (50 μM NH₄⁺, i.e. 0.7 mg N 1⁻¹) of inorganic ions. Once the equilibrium is reached (i.e. the cell population is conditioned and the nutrient concentration is zero), in a second phase, the starved cells are mixed with a secondary effluent which has a higher nutrient content (200–400 μM NH₄⁺, i.e., 2.8–5.6 mg N 1⁻¹). Ion depletion (NH₄⁺, NO₃^-, NO₂^- and PO₄^3-) follows specific kinetics; successive identifiable stages related to photoperiod lead to a complete stripping of nutrients. In addition to ion concentrations, pH and cell population were determined every 2 h during the experiment. Results and conclusions are presented.     

Growth of Selenastrum capricornutum in natural waters augmented with detergent products in wastewaters

A determination of whether the removal of phosphate builders from detergents would modify the ability of domestic secondary treated sewage effluent to stimulate the growth of a test alga (Selenastrum capricornutum-Printz) in receiving waters alone and augmented with detergent products was made. The lakes used as sources of test waters were located in northeastern New York State and possessed total phosphorus concentrations ranging from ca. 0.01 to 0.04 mg P1⁻¹.

The alga experienced stimulation in all three test lake waters from secondary sewage containing detergent with phosphate or detergent without phosphate. A concentration of 60 μg P 1⁻¹ was sufficient to effect significant algal growth in two of the test waters; however, concentrations ranging up to 110 μg P 1⁻¹ did not generate such a response in the third test water. This latter result and others suggested that neither phosphorus nor other nutrients from these wastewater additions were the factors fully accountable for the observed response(s).     

进水以高浓度工业废水为主的污水处理厂扩建工程设计

浙江某污水厂进水中含有70%的工业废水,具有有机物浓度高、冲击负荷大、乳化油浓度较高的水质特点,且出水水质要达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)中一级A标准。已建一期工程(2×10⁴m³/d)采用AAO+高效沉淀池+滤布滤池工艺处理污水,出水有机物超标严重。为此,二期扩建工程(2×10⁴m³/d)采用调节池+混凝气浮组合池+A/O生化池+高效沉淀池的工艺流程。设计中增设调节池调节进水水质水量;采用混凝气浮组合池去除进水中的乳化油,以避免对后续工艺运行造成干扰;延长生化池停留时间,强化对有机物的去除,避免在深度处理阶段设置高级氧化工艺,节省建设、运行费用;气浮污泥采用离心脱水,生物污泥采用带式脱水机处理。工程试运行期间出水水质稳定达到设计标准,直接运行成本为0.56元/m³。