Influence of application of sewage sludges, and sludge and manure composts on plant Ca and Mg concentration and soil extractability in field experiments

Application of organic waste influences crop uptake of Ca and Mg and soil extractability, depending on the nature of the crop and the waste. Four organic wastes: (i) digested sewage sludge (DSS), (ii) irradiated sludge (DISS), (iii) composted sludge (DICSS), and (iv) composted livestock manure (CLM) were applied for two years at rates of 10, 20, 30, and 40 Mg solid ha^-1 year^-1. Fertilizers N and K were applied to the control treatment (CT), as well as to the waste treatments to supplement crop growth across all treatments, so that these nutrients were not treatment variables. Calcium and Mg concentrations in the tissue of lettuce, bean pods and petunias in 1990 and two cuts of lettuce in 1991, and the CH₃COONH₄-extractable soil Ca and Mg were determined. Concentration of Ca and Mg in bean pods did not change to the waste application. Calcium concentration in bean pods was less than half of that in other crops. Magnesium concentration in bean pods and petunias was same, but was much lower than in lettuce. Application of DSS, in general, increased Ca concentration in the crops more than did other wastes. The extractable soil Ca was positively correlated with Ca applied with DISS (r=0.453, P<0.05). Although only a limited amount of Ca was supplied with CLM at the rate of 10 Mg solid ha^-1(40 kg Ca ha^-1), Ca concentration in petunias increased significantly, then, decreased with increased Ca application (r=0.453, P<0.05). A similar pattern with CLM was found in the extractable soil Ca. The waste application from all the sources had no influence on crop Mg concentration in 1990, possibly due to low Mg concentration in the wastes. While continuously applied DSS and DISS in 1991 linearly increased Mg concentration in both cuts of lettuce (r=0.867, P<0.01; r=0.670, P<0.01 and r=0.671, P<0.01; r=0.665, P<0.01 for first cut and second cut of lettuce with DSS and DISS application respectively), application of CLM decreased Mg concentration in first cut lettuce. The patterns of extractable soil Mg were opposite to crop Mg concentration, as the extractable soil Mg linearly increased with CLM, and decreased with the high rate of DSS application. The ability of wastes to supply N was an important factor influencing crop cations (K, Ca and Mg) uptake.     

Effect of air temperature and aeration strategy on water removal during sewage sludge composting

Water removal is one of the main objectives of sewage sludge composting to reduce the volume and mass of sewage sludge. In this study, the effect of aeration strategy and ambient temperature (summer and winter) on composting pile temperature, moisture content, and volatile solid (VS) change were studied during sewage sludge composting processes in a well-operated sludge composting plant. The results showed that the temperatures of the composting pile could remain above 55°C for more than 3 days under all conditions, which was sufficient to meet the requirement of harmless treatment. Moisture content of composting material decreased from 65%–69% to 39.2%–52.6% within 20 days, and VS decreased to about 77%. In the end of the composting process, cumulative water removal was 0.45–0.47?kg/kg in summer, which was significantly higher than that in winter (0.35–0.36?kg/kg). When the average aeration rate was fixed, aeration strategy with a smaller aeration rate and higher on/off time ratio showed more water removal than that with a higher aeration rate and lower on/off time ratio in summer, but showed reverse results in winter.     

Soil fertility effects of repeated application of sewage sludge in two 30-year-old field experiments

Recirculation of plant nutrients from waste materials back to agriculture is necessary in a sustainable food production system. In this study we investigated the long-term effect of direct land application of sewage sludge (SS) on soil fertility on two Swedish farms, where field experiments were set up in 1981 with three rates of SS (0, 4 and 12 Mg dry matter ha^?1 every 4 years) and three rates of mineral fertilisation, in a factorial design with four replicates. At one site, SS application tended to increase crop yield over time but, when plant nutrients were not limiting, the effect was only significant for spring barley. We deduced that improved soil structure was the main driver for this fertility enhancement after SS application, as indicated by lower soil bulk density and higher soil carbon concentration. After 30 years, soil organic carbon stocks to 0.40 m depth differed by up to 17 Mg ha^?1 between treatments. According to carbon balance calculations, retention of carbon derived from SS ranged between 18 and 20% for the soil layers analysed at the two sites. Soluble phosphorus (P) increased with sludge application rate, but represented only around 2% of the expected residual P according to P-balance calculations. The fertiliser value of nitrogen was also low, with only 3–8% nitrogen use efficiency. Heavy metals such as copper, zinc and mercury showed moderate accumulation in the soil, but elevated levels of metals were not detected in crops, even at the highest dose of SS. These results show that SS represents a valuable resource for improving soil fertility in terms of soil organic matter and soil structure, but its efficiency for nutrient cycling is very low within the time frame considered in the study.     

Application of liquid cattle manure and inorganic fertilizers affect dry matter,nitrogen accumulation,and partitioning in maize

Efficient use of N applied in the form of organic and inorganic fertilizers is important in maize (Zea mays L.) production to maximize producer’s economic returns and maintain soil and water quality. A field study was conducted for three consecutive years (2003–2005) in Thessaloniki, Greece to investigate whether liquid cattle manure can be used to replace inorganic fertilizers and also whether inorganic fertilizer can be applied preplant or as a combination of preplant and sidedress and can affect maize growth, development and N use efficiency. The treatments were control (unfertilized), liquid dairy cattle manure (Manure), application of 260 kg N ha⁻¹ year⁻¹ as basal dressing (N-single), application of 130 kg ha⁻¹ year⁻¹ N as basal dressing before sowing and 130 kg N ha⁻¹ when plants were at the eight-leaf stage (V8) (N-split). In 2 out of the 3 years of the study there was a significant positive effect of fertilizer application on maize growth, development, N uptake, and partitioning compared with the control. Dry matter production was increased by an average of 39% during the 2 years in plots fertilized either with manure or inorganic fertilizers than the control plots. Also from the yield components kernel weight per ear and number of kernels per ear were increased by an average of 35% and 32%, respectively in the fertilized plots compared with the control plots. Chlorophyll level was affected as it was increased by an average of 18%, 14%, and 18% at the ten-leaf stage (V10), silking and milk stage, respectively in the fertilization treatments compared with the control. Similar trend was observed in the other parameters that were studied. No differences were found between the manure and the different times of N application which indicates that manure can be used to replace inorganic fertilizer. Applying N either preplant in a single application or in split application (half of N preplant and half as sidedress) did not have any effect on any characteristics that were studied indicating that preplant application can be used as it is more cost effective. The present study indicates that liquid cattle manure can be used to replace inorganic fertilizers and also that there was no difference between preplant and sidedress application of N.     

Comparisons of the fertilizing and liming properties of lime-treated sewage sludge with its incinerated ash

Two field experiments were conducted to compare the fertilizing and liming properties of dried lime-treated sewage sludge with its incineration product (ash). One experiment used a mixture of ryecorn and ryegrass on a relatively fertile soil and the other lucerne on a strongly acidic and phosphorus deficient soil.The first harvest of the ryecorn-ryegrass experiment showed small but significant linear responses in dry matter yield to both ash and sludge. Ash applications did not affect foliage nitrogen and phosphorus concentrations, or uptakes, but sludge applications increased these significantly. Sludge also increased the concentrations of K, S, Mg, Cu and Zn but ash only increased the concentrations of S and Mg. At the second harvest (ryegrass) 5 t ha^–1 of sludge increased dry matter yield and foliage nitrogen and phosphorus concentrations whereas ash had no effect. Levels of phosphorus extracted from the soil were increased by both amendments but the sludge was much more effective than the ash. Both ash and sludge raised soil pH.In the lucerne experiment comparisons between sludge and ash were calculated from response surfaces fitted to the data which showed marked increased in soil pH and dry matter yield. Sludge markedly increased extractable phosphorus whereas ash had no effect. The sludge was 22% as effective as ash in raising soil pH to 6.5. The amounts of ash required to obtain the same yield as 10 t ha^–1 of sludge were 5.78, 12.78 and 6.39 t ha^–1 respectively for three successive harvests. These results and those for foliage concentrations of nitrogen and phosphorus were also ascribed to the much greater availability of the sludge phosphorus than the ash phosphorus, and the presence of nitrogen in the sludge but not in the ash.     

Phosphorus availability from phosphate rock and sewage sludge as influenced by the addition of water soluble phosphate fertilizer

Phosphorus (P) inputs are required for sustainable agricultural production in most acid soils of the tropics and subtropics. Phosphate rocks (PR) and organic materials have been suggested as alternative P sources in these soils. Quantitative information on the P availability from sewage sludge (SL) is scanty. Methods to improve the effectiveness of PR such as partial acidulation and compaction with water-soluble P sources have been recommended. The objective of this greenhouse study was to evaluate the relative agronomic effectiveness (RAE) of Florida PR and sewage sludges (irradiated and non-irradiated) applied alone and in mixture with a water-soluble source (triple superphosphate, TSP) at two rates (50 and 150 mg P kg^–1 soil). The ³²P isotope dilution technique was utilised to determine the proportion of P in the plant taken up from the P fertilizer treatments. Wheat was grown on an acid loamy sand Dystric Eutrocrepts and harvested 6 weeks after planting. Results on total P uptake and the RAE of the P fertilizer sources tested indicated that the addition of 50 mg P kg^–1 soil as TSP was adequate in supplying P to the 6-week-old wheat plants as compared to PR and sewage sludge. Intermediate values were obtained for the mixtures. Similar responses were observed for the high P rate. For a given P rate, phosphorus uptake from PR and SL in presence of TSP was higher than P uptake from these sources alone, indicating an enhancement effect of TSP on the effectiveness of these non-readily available sources. With respect to P uptake from PR applied alone, the relative increases in P uptake from PR due to TSP influence were 52 and 67% for the low and high P rates, respectively. The relative increases in P uptake from SL due to TSP when compared to P uptake from SL alone were 102 and 59% for the low and high P rates of application. Application of a water-soluble P fertilizer together with a non-readily available P source shows an enhancement on the P uptake from the non-readily available P source by the wheat plants. In this experiment the estimated enhancement effects are very likely underestimated.     

Extraction and characterisation of extracellular polymers in digested sewage sludge

Five different bacterial extracellular polymer extraction methods were compared on digested sewage sludge. A washing step was necessary to remove and eliminate the slime from the sludge sample, in order to distinguish it from the material more tightly bound to the sludge solids. An ion-exchange resin method was the most effective and least disruptive of all treatments tested, based on the relatively high extracellular polymer yield and the small amount of cell disruption demonstrated by the fractionation and characterisation of the extracted material. The extracellular polymer extracted contained protein and polysaccharide in a ratio of approximately 3:1, and contributed a relatively small proportion of the total solids in digested sludge. This was comparatively less than is extracted in activated sludge. The ion-exchange resin method yielded 1% by weight of polysaccharide and 3% of protein, whereas ethanol-insoluble material accounted for 3.5% of the solids in digested sludge.     

化肥企业必须严格贯彻"节水·治污·利用"方针

20世纪世界淡水消费量增加6倍,其中工业用水增加约26倍,预测淡水短缺是21世纪面临三大生态问题之一.我国水资源居世界第6位,但人年均水量为世界水平的1/4,列世界第121位,预测2010年内进入严重缺水期,缺水高峰期在2030年左右.我国不但缺水,而且用水浪费、污染水源和利用率低.化肥是用水和排污大户,只要严格贯彻国家有关环境、治污等法规和标准,可以做好节水、治污和利用.     

Effect of long-term application of sewage sludge to a grazed grass pasture on organic carbon and nutrients of a clay soil in Zimbabwe

A study was conducted to assess the nutrient status of a Zimbabwean vlei clay soil grown to a Kikuyu (Pennisetum clandestinum Chiov.) grass pasture which had been amended with sewage sludge for 19 years. There was a significant (P<0.05) accumulation of organic C, mineral N, resin extractable P, and exchangeable K, Ca, Mg and Na in the top soil horizon. Organic C increased from 2.5 to 8.7% and 1.8 to 4.5% in the 0–5- and 5–10-cm horizons, respectively. Addition of sewage sludge resulted in a 19- and 57-fold increase in extractable P in the 0–5- 5–10-cm soil horizons, respectively. Exchangeable Na significantly (P<0.05) increased from 0.88 to 4.10 cmol/kg and from 1.04 to 3.06 cmol/kg in the 0–5- and 5–10-cm horizons, respectively. It was concluded that sewage sludge is a valuable source of nutrients and also provides an opportunity to increase soil organic matter.     

Lignocellulose biodegradation in the biodrying process of sewage sludge and sawdust

Lignocellulose degradation is important when applying biodrying treatment to sewage sludge intended for land use. This study investigated the lignocellulose degradation in the biodrying of sewage sludge and sawdust. The experiment analyzed lignocellulose content, lignocellulase activity, humic substances, and fungal communities. After biodrying, lignin, cellulose, and hemicellulose degradation rates were 48.4, 38.8, and 45.0%, respectively. Carboxymethyl cellulase, lignin peroxidase, and xylanase played key roles. During the thermophilic phase, more than 80% of the microorganisms in the sample contributing to lignocellulose degradation were Ascomycota. The lignocellulose degradation and a rate of increase in humic acid/fulvic acid of 380% benefit land use of biodrying product.     

酸化水解-活性污泥-生物接触氧化工艺处理有机污水

介绍了采用酸化水解——活性污泥——生物接触氧化工艺处理含有山梨醇、甘露醇、蔗糖、醋酸乙烯、甲基纤维素的有机污水。该工艺具有出水水质稳定，操作简单、管理方便，能耗低等优点，是处理该类有机污水的有效方法。     

Kinetic studies of the pyrolysis of sewage sludge by tga and comparison with fluidized beds

The pyrolysis of sewage sludge was examined by thermogravimetric analysis using different heating rates, particle sizes and final temperatures. A semi-empirical model was developed with four global consecutive/competitive reactions to volatile and solid products including also a heat balance. This model was extrapolated to isothermal reactor conditions and compared to experimental data on fluidized bed pyrolysis. Depending on the particle size and reactor temperature, about 90% of the maximum conversion in a fluidized bed takes place under external heat transfer control, the rest under kinetic control. Incomplete conversion occurs at short particle residence times, which were calculated approximately by the model.     

微波制备污泥质活性炭吸附剂及其再生研究

以城市污泥为原料,磷酸和氯化锌为活化剂,微波制备活性炭吸附剂,考察了活化剂浓度、浸渍时间、微波功率和辐射时间等对活性炭产率和吸附性能的影响。结果表明,活性炭对亚甲基蓝吸附值为86.2 mL/g,碘的吸附值为806.0 mg/g。用该活性炭处理含铬废水后再生,其亚甲基蓝吸附值为89.4 mL/g,碘的吸附值为795.3 mg/g,并且再生前后活性炭对含铬废水均有较好的处理效果。该方法操作方便,缩短了活性炭的制备和再生时间,再生效果好。     

CPAM在污泥脱水工艺中的絮凝效果研究及应用

以生活污水为絮凝对象,研究了不同的原水浊度、pH值和温度条件下,阳离子聚丙烯酰胺(CPAM)的投加量、搅拌时间对絮凝效果的影响。实验结果表明,CPAM作为污泥脱水工艺中的净水絮凝剂,在絮凝反应中加入0.3~0.6 mg/L,搅拌时间占总絮凝反应时间的2/3时,可获得最佳絮凝沉淀效果。分析了在实际生产过程中CPAM溶解方式、投加方式对絮凝效果的影响,应用结果表明,该工艺可使水厂出水水质得到明显提高,在保证水质和不增加净水成本的前提下,还可以使生产能力大幅度提高。     

Using sewage sludge as a permeable reactive barrier for remediation of groundwater contaminated with lead and phenol

We investigated the efficiency of granular dead anaerobic sludge (GDAS) biosorbent as a permeable reactive barrier for remediation of groundwater contaminated with lead–phenol (Pb-Ph) present simultaneously. Batch tests were performed to characterize the equilibrium sorption properties of the GDAS and sandy soil in the Pb-Ph containing aqueous solutions. Computer solutions (COMSOL) Multiphysics 3.5a software was used for simulating the two-dimensional equilibrium transport of lead–phenol including the sorption process through the saturated sandy soil in the presence of GDAS. A good agreement between the predicted and experimental results was recognized with the root-mean-squared error not exceeding 0.049.     

Laboratory and greenhouse assessment of plant availability of organic N in animal manure

Laboratory data (thermal fractionation, pepsin extraction, C:N_o ratio) of dung and manure were mutually compared and contrasted with plant-availability of organic N (N_o) as found in a greenhouse experiment according to the double-pot technique. Two types of fresh cow dung (one with a relatively wide and the other with a relatively narrow C:N_o ratio) and four types of manure (from poultry, sheep, pigs and cow) were compared with ammonium nitrate as chemical reference fertilizer. Relative effectiveness of organic N (RE_o) was used as characteristic; it was calculated as the fraction of organic N that has the same availability to plants as inorganic N. RE_o for poultry and sheep manure could not be assessed, probably because of NH₃ volatilization causing direct damage to plants and N losses. RE_o values decreased in the order: dung with narrow C:N_o > dung with wide C:N_o > pig manure > cow manure. Thermal fractionation did not provide a suitable index of plant-availability of organic N. Pepsin extracted organic N gave a positive, and C:N_o ratio a negative relationship with RE_o. Also between pepsin extracted organic N and C:N_o ratio a negative relationship was found. As C:N_o ratio is relatively easy to determine, it is considered the most practical laboratory index for plant availability of organic N in animal manures low in ammonia. When using the double-pot technique, application rates of manure types high in ammonia should be restricted.     

Experimental and theoretical research on agitated contact drying of sewage sludge in a continuous paddle dryer

Sludge drying is an important intermediate process for sewage sludge treatment, usage, and disposal. A series of drying experiments were conducted in a continuous paddle dryer in order to have a better understanding of the sludge drying mechanism. The couple model of penetration model and Markov chain was used to simulate the drying kinetics in a continuous paddle dryer. The drying process has been compared in experimental and theoretical results, which show good agreement. The sewage sludge drying process in a continuous paddle dryer can be divided into three stages: the pasty phase, the sticky phase, and the complete-granular phase. The influences of the drying parameters on the sludge drying kinetics in a continuous paddle dryer were investigated. The sludge flow rate, dryer wall temperature, and dryer slope have remarkable influence on sludge drying in the examined range, but the stirrer speed and steam temperature have little influence on the drying kinetics.     

文中油田污水降油处理改造及效果评价

文中油田产出水中油含量高,降油及相关污水处理难度大,处理后水质指标低,为此,分别进行了室内降油试验和现场改造应用。结果表明,含油大幅下降,现场水质指标明显提高,能够满足油田注水水质要求。     

Properties of water-soluble and insoluble particulate matter emitted from dewatered sewage sludge incineration in a pilot-scale ash melting furnace

Emission of inorganic particulate matter (PM) from the incineration of dewatered sewage sludge has been investigated in a novel ash melting furnace. The sludge containing 79 wt% water was incinerated in an oxygen-enriched atmosphere at the primary temperature of 1400 °C, and its unburned volatile was combusted at 1100 °C in a secondary combustion chamber. A 13-stage low-pressure-impactor and the conventional impinger methods were employed for PM sampling at the outlet of the secondary combustion chamber. The results indicate that, PM is dominated by volatile and semi-volatile elements including Br, Cl, P, S, Na, K, Zn, As, Cu, Mn and Ni. Less refractory elements were found. PM has two major fractions: <0.22 and ?0.22 μm. Their chemical forms as well as water solubility are different between two fractions. The majority of Br, nearly half of Cl, and 40% of S and P are present in the small fraction. They are mostly water-soluble due to the association with alkali elements and heavy metals. The water-insoluble calcium sulfate and calcium/iron phosphate were, however, found in the large fraction of PM. Regarding the cations, the water solubilities of Na, K, Mn and Ni are close to their proportions partitioned into the small fraction of PM, since their water-soluble species were preferentially formed in this fraction. A relatively weak correlation for Al, Ca and As, while no such a correlation were found for Cu, Zn and Fe, due to the complex compounds formed for them.     

文东油田污水降铁处理及现场效果评价

文东油田产出水中Fe^2 含量高,降铁及相关污水处理难度大,处理后水质指标低,对此,进行了室内降铁试验和现场应用。结果表明,污水指标较原来明显提高,能够满足油田注水和防腐要求。