Evaluation of plant bed filter ditches for the removal of T-N and T-P from eutrophic pond water containing particulate N and P

Cultivation of useful terrestrial and aquatic plant species in plant bed filter ditches enables to treat domestic wastewater in addition to resource recycling and amenity functions. We reported previously that a ditch planted with papyrus removed Nand P most effectively from artificial wastewater. We evaluated the effectiveness of plant bed filter ditches in the treatment of eutrophic pond water, which unlike artificial wastewater, contains particulate Nand P. Experimental ditches were planted with papyrus, African marigold, peppermint, and impatience. These plant species were effective in removing N and P from artificial wastewater and could be used by rural communities for the production of handicrafts, cut flowers, and ornamental purposes. The control ditch did not contain plants (plant-free ditch). Pond water was continuously supplied to the ditches at a loading rate of 0.6–0.9 g m^-2 d^-1 for Nand 0.2–0.35 g m^-2 d^-1 for P. In the plant-free ditch, particulate Nand P in the influent were removed by passage through the bed filter, unlike NO³-N and PO⁴-P. A larger amount of PO⁴-P was dissolved from particulate P in the bed filter. The planted ditches effectively removed NO³-N, PO⁴-P as well as particulate Nand P. The planted ditches were able to purify eutrophic pond water, resulting in clear water with a concentration below 0.3 mg L^-1 for N and 0.02 mg L^-1 for P, concentrations at which water bloom does not occur. The average removal rate of pollutants by the planted ditches during the experiment, except for the first 2 weeks, was 0.67 g m^-2 d^-1 for total N and 0.03 g m^-2 d^-1 for total P. We recommend that plant bed filter ditches containing papyrus and flowers be used for ornamental purposes and removal of N and P from pond water along with the supply of clear water as ornamental streams.     

Evaluation of useful plants for the treatment of polluted pond water with low N and P concentrations

Eutrophication of ponds for agricultural use has begun to adversely affect rice production and the residential living environment in Japan. Cultivation of useful terrestrial and aquatic plant species in plant-bed filter ditches enables to treat domestic wastewater in addition to resource recycling and amenity functions. We evaluated the ability of several plant species, Italian ryegrass (Lolium multiflorum Lam.), hanana (Brassica campestris L. var.), African marigold (Tages erecta L.), sorghum (Sorghum vulgare Pers.), kenaf (Hibiscus cannabinus L.), papyrus (Cyperus papyrus L.), and reed (Phragmites communis Trin.), to remove nitrogen and phosphorus from polluted pond water whose N and P concentrations were much lower than those in domestic wastewater. Artificial pond water containing 2.5 mg L^-1 of N and 0.5 mg L^-1 of P was supplied to ditches at a loading rate of 1.1 g m^-2 d^-1 for N and 0.21 g m^-2 d^-1 for P. Italian ryegrass, papyrus, or kenaf in ditches removed N and P more effectively than other plants. The average removal rate of Italian ryegrass in ditches was 0.62 g m^-2 d^-1 for N and 0.10 g m^-2 d^-1 for P, that of papyrus 0.81 g m^-2 d^-1 for N and 0.15 g m^-2 d^-1 for P, and that of kenaf 0.73 g m^-2 d^-1 for N and 0.11 g m^-2 d^-1 for P. The influence of N and P concentrations on the removal rates of Italian ryegrass, papyrus, and kenaf was studied. Concentrations at a removal rate of zero were 0.2–0.3 mg L^-1 for N and 0.01–0.03 mg L^-l for P. At low concentrations, the plant removal rates increased sharply with the rise in the concentration. When N concentrations exceeded 0.3–0.6 mg L^-1 and P concentrations 0.10–0.45 mg L^-1, the removal rates were high and less affected by the concentration. It was considered that these plant species could be used most efficiently at the concentrations where removal rates are less restricted.     

Ammonia Nitrogen Removal in Step-Feed Rotating Biological Contactors

The effect of step-feed on biological ammonia nitrogen (NH₃-N) removal in a rotating biological contactor (RBC) system consisting of two three-stage units (one control and one step-feed) treating synthetic wastewater was examined. The performance of the step-feedRBC was evaluated in comparison to a regularly fed RBC in terms of NH₃-N removals and stage-dissolved oxygen (DO) conditions over a range of hydraulic and organic loading rates (HLR = 0.032 to 0.125 m³ m^-2. d^-1 and OLR = 11.03 to 111.6 g COD m^-2. d^-1). The results indicate that the step-feed unit showed better removal efficiency (%) at high HLR and ORL than the regularly fed control unit. Increasing the HLR and the OLR resulted in a decrease in DO in all the stages of the two units. However, DO values in the step-feed system were higher than those recorded for the control system. In addition, O₂ limiting conditions (DO ≤ 2 mg l^-1) and heavy growth of Beggiatoa were detected in stage 1 of the control unit at high loading rates.     

Treatment of Hydroponics Wastewater Using Constructed Wetlands in Winter Conditions

Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate and phosphorus but contains almost no organic carbon. Constructed wetlands (CWs) have been proposed to treat this type of effluent, but little is known about the performance of these systems in treating hydroponic wastewater. In addition, obtaining satisfactory winter performances from CWs operated in cold climates remains a challenge, as biological pathways are often slowed down or inhibited. The main objective of this study was to assess the effect of plant species (Typha sp., Phragmites australis, and Phalaris arundinacea) and the addition of organic carbon on nutrient removal in winter. The experimental setup consisted of 16 subsurface flow CW mesocosms (1 m², HRT of 3 days) fed with 30 L?d¹ of synthetic hydroponics wastewater, with half of the mesocosms fed with an additional source of organic carbon (sucrose). Carbon addition had a significant impact on nitrate and phosphate removal, with removal means of 4.9 g m^-2?d^-1 of NO₃-N and 0.5 g m^-2 d^-1 of PO₄-P. Planted mesocosms were generally more efficient than unplanted controls. Furthermore, we found significant differences among plant treatments for NO₃-N (highest removal with P. arundinacea) and COD (highest removal with P. australis/Typha sp.). Overall, planted wetlands with added organic carbon represent the best combination to treat hydroponics wastewater during the winter.     

Oxygen Transfer and Industrial Wastewater Treatment Efficiency of a Vertically Moving Biofilm System

A vertically moving biofilm system (VMBS) was developed to treat wastewater. In this system, the biofilm grows on a biofilm module consisting of plastic media that is vertically and repeatedly moved up into the air and down into the water. The objectives of this study were to investigate the oxygen transfer efficiency and industrial wastewater treatment performance of the VMBS. The oxygen transfer coefficient (K _L a) depended on the movement frequency (n) of the biofilm module and was proportional to n ^1.67. K _L a values measured were within the range of 0.0001 to 0.0027 s^-1. The VMBS exhibited good carbonaceous removal when treating industrial wastewater produced in a factory manufacturing synthetic fibres. Removal efficiency of filtered chemical oxygen demand (COD) and biological oxygen demand (BOD₅) was up to 93.2 and 97.9%, respectively. The volumetric removal rates of filtered COD and BOD₅ reached 1320 g COD m^-3 day^-1 and 700 g BOD₅ m^-3 day^-1. The areal organic removal rates, based on the surface area of the biofilm substrata, were 16 g BOD₅ m^-2 day^-1 and 39 g COD m^-2 day^-1. No clogging occurred during the experiment. The mean areal biofilm mass increased with increasing the mean areal BOD₅ removal rate. The new biofilm process has such advantages as high carbonaceous oxidation, energy saving, simpleconstruction and easy operation for industrial wastewater treatment.     

Losses of Soil Carbon upon a Fire on a Drained Forested Raised Bog

We studied the consequences of a fire that affected 29 ha of a drained forested raised bog in Tver oblast, Central European Russia. The drainage network consisted of open 1-m-deep ditches with 60 to 160 m ditch spacing. The groundwater level (GWL) varied within the studied drained bog. We used the method of assessing the loss of soil carbon (C) based on the difference between the ash concentration in the burnt peat of the upper layer and underlying unburnt layers. The carbon loss was higher near the drainage ditches than in the sites remote from ditches. The sample median values of carbon loss (kg C/m²) were estimated at 0.37 near the drainage ditches and at 0.22 for the remote sites with a distance of 160 m between ditches. They increased to 2.23 and 0.79 near and far from the drainage ditches for 106 m ditch spacing, and ranged from 1.13 to 2.10 near the drainage ditches and were equal to 0.45 at the remote sites for 60 m ditch spacing. The maximum loss of C was at the bog margin with the 70-cm-deep GWL; the sample median was equal to 2.97 kg C/m². The results obtained for C loss from the wildfire on the raised bog agree with the estimates obtained by other authors (1.45–4.90 kg C/m²) and confirm the importance of taking such loss into account in the estimates of the carbon budget of peat soils (Histosols).     

人工布设基质对农田排水沟水质的影响

本研究选择宁夏灵武农场的典型排水支沟进行人工布设基质,在沟中布设土壤、炉渣、秸秆、锯末4种基质处理及铲草处理和对照(不做任何处理),研究分析了基质对农田排水沟水质的影响。对基质的组分分析表明,锯末显著地吸附盐分和全氮,吸附量分别达0.4 g.kg 1和0.3 g.kg 1,土壤、炉渣、秸秆均明显地释放盐分,释放量为5.3~50.8 g.kg 1;秸秆显著地释放有机碳,释放量达54.0 g.kg 1;4种基质对全磷吸附效果不明显。水质分析表明,除秸秆处理和对照外,盐分(TDS)在其他处理下显著减少,而化学需氧量(COD)、总氮(TN)、总磷(TP)、NO3-N和NH4+-N浓度在锯末和土壤处理下均有不同程度的减小。对于整条试验沟道,农田退水中TDS、TN、TP的浓度随着在沟道迁移距离的增加呈明显减小的趋势,至出水断面时浓度分别为0.60~0.80g.L 1、0.24~0.33 mg.L 1和0.04~0.09 mg.L 1。田间沟道试验说明,农田排水沟能有效地截留农田退水污染物,选择适合的基质进行人工布设实际可行,有助于发挥农田排水沟的生态功能。     

水生植物刈割对生态沟渠中氮、磷拦截的影响

本研究选用生态沟渠中水生美人蕉、铜钱草、黑三棱、穗花狐尾藻和灯心草作为试验植物,通过比较刈割区和未刈割区底泥样和植物样氮、磷含量及水样氮、磷去除率,分析刈割措施对生态沟渠拦截氮、磷效果的影响。结果表明,5种植物(300 m2)2次刈割试验共带走全氮11.889 kg和全磷1.099 kg;其中,不同植物收获全氮表现为水生美人蕉(7.686 kg)>穗花狐尾藻(1.501 kg)>铜钱草(1.128 kg)>灯心草(0.974 kg)>黑三棱(0.601 kg),收获全磷表现为水生美人蕉(0.433 kg)>穗花狐尾藻(0.233 kg)>黑三棱(0.191 kg)>铜钱草(0.134 kg)>灯心草(0.109 kg)。刈割管理还可以提高沟渠底泥中氮、磷的去除率(黑三棱除外)。与未刈割区相比,刈割提高底泥全氮和全磷的去除率次序分别为穗花狐尾藻(20.73%)>铜钱草(20.00%)>灯心草(16.05%)>水生美人蕉(4.86%)>黑三棱(9.72%)和灯心草(20.69%)>铜钱草(16.67%)>水生美人蕉(4.55%)>穗花狐尾藻(0.00%)>黑三棱(16.00%)。刈割后的水体氮、磷去除结果也说明植物刈割可以提高水生植物对氮、磷的净化效果。因此,植物刈割管理既能直接转移出沟渠中的营养物质,也提高了沟渠底泥和水体中氮、磷的去除效率。     

Soil and Minespoil Fill as Media for Renovation of Nitrogen and Phosphorus in Domestic Wastewater

Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m^-2d^-1) and spoil-fill columns at one loading rate (21.6 L m^-2d^-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO₃ ^- + NH₄ ⁺), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO₃ ^--N concentrations were still above the 10 mg^-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L^-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.     

Assessment of Biogas use as an Energy Source from Anaerobic Digestion of Brewery Wastewater

Energy recovery from a crossflow ultrafiltration (UF) membraneunit employed in order to improve the performance of an anaerobic contact digester for the treatment of brewery wastewater was assessed. The performance of the pilot-scale anaerobic UF membrane system was studied for over 15 months. At steady-state conditions, an organic loading rate of 28.5 kg COD m^-3 d^-1, a hydraulic retention time of 4.2 days and overall COD and BOD removal efficiencies of 99% and almost 100% were achieved, respectively. Percent methane in biogas was found to be in a range of 67–79% with the corresponding methane yield of 0.28–0.35 m³ CH₄ kg^-1 COD_removed. The potential energy recovery from the system treating brewery wastewater at an OLR of 28.5 kg COD m^-3 d^-1 was 87 MJ d^-1 which would enable to maintain all energy requirements of the feed pump, mixing and heating of the reactor contents. In addition to this, 71% of the energy requirement for recirculating the reactor content through the membranes would also be recovered.     

A comparative study of permeable layer materials and aeration regime on efficiency of multi-soil-layering system for domestic wastewater treatment in Thailand

Abstract

Multi-soil-layering (MSL) system was designed for purifying domestic wastewater and for treating polluted river water. MSL system is typically comprised of layers of soil mixture blocks alternating with permeable layers. The permeable layer has roles of preventing clogging and to increasing the efficiency of infiltration of wastewater through the soil mixture blocks. In this study, the comparative efficiency of five MSL systems as a function of five permeable layer materials (zeolite, zeolitized perlite, perlite, gravel, and charcoal) was investigated. The MSL systems were constructed in 15 × 50 × 100 cm boxes where the soil mixture blocks contained sandy clay soil, kenaf + corncob, and iron scraps at a ratio of 6 : 1 : 1 by weight, respectively, and filled up in alternation with the permeable layer. The results indicated that all the MSL systems at loading rates of 96–346 L m^?2 d^?1 under nonaerated conditions were able to reduce the levels of COD (342–1,231 mg L^?1), BOD₅ (201–802 mg L^?1), and soluble reactive phosphorus (SRP) (3.5–10.1 mg P L^?1) at percentages of 79.0–98.1, 80.0–99.6, and 97.1–100%, respectively. The zeolite and the charcoal-based MSL systems under a 96–346 L m^?2 d^?1 loading rate effectively reduced the level of TN (41.4–65.5 mg N L^?1) at percentages of 79.0–92.1 and 30.7–88.9%, respectively. In terms of prevention of clogging, the charcoal-based MSL system was the most effective, followed by the gravel and zeolite-based MSL. The apparent efficiency of pollutant removal, for zeolitized perlite, perlite, and gravel-based MSL systems was low. With an on-off aeration operation, the efficiency of the MSL systems in the reduction of the levels of COD, BOD₅ , and SRP (hereafter reference to as “removal”) was significantly enhanced. Overall, the zeolite-based MSL system seemed to be more effective than the other MSL systems. However, if optimum aeration could be obtained, the removal efficiency of charcoal-based MSL system might be improved. Aeration at a rate of 64,000 L m^?3 d^?1 for 1 week alternating with 2 weeks of nonaeration enhanced the removal of COD, BOD₅ , and SRP but not that of TN.     

沟渠及塘堰湿地系统对稻田氮磷污染的去除试验

为研究原位状态下灌区沟渠及塘堰湿地系统对稻田氮磷污染的去除效应和规律,在湖北省漳河灌区选取农沟-斗沟尺度的3段典型排水沟渠和一处塘堰,分别于2009-2010年5—9月水稻生育期在沟渠和塘堰进出水口采集水样进行氮磷浓度化验分析。结果表明,灌区农沟-斗沟尺度典型排水沟渠对总氮、硝态氮、铵态氮、总磷整体去除率分别为44．6％、9．9％、37．3％、35．1％;塘堰对总氮、硝态氮、铵态氮、总磷的平均去除率分别为15．2％、15．6％、30．2％、-6．5％。典型沟渠和塘堰对氮磷污染的去除表现出一定的抗冲击自修复性。原位条件下,由于排水沟中水力停留时间都不长,使得种植不同植被的沟段之间对氮磷的去除效应差异性不明显。塘堰湿地系统中植被的选育及其管理对去除稻田排水氮磷污染具有重要意义。     

肉鸭粪便排放特征的季节性变化

本研究旨在探讨肉鸭粪便的特性,并对其不同季节的污染物排放特征进行评价,为肉鸭养殖场废弃物处理和资源化利用提供依据。分4个季节进行了北京Z型肉鸭饲养试验(饲养期37 d),记录采食量、产粪量,并定期测定饲料和粪便中水分和有机质含量及总氮(TN)、P、Cu、Zn含量。结果表明:肉鸭粪便中Zn含量秋季最高, TN、P、Cu含量均为冬季最高;冬季粪便中TN含量极显著高于夏、秋两季(P0.01); P、Cu含量在冬季均极显著高于其余季节(P0.01);粪便中Cu、Zn含量均为春季最低。肉鸭粪便平均含水率为84.61%,夏季最高,春季最低;平均有机质含量为83.38%,表现为冬春秋夏。春夏秋冬四季的粪便产生量分别为338.3g?d~(-1)?只~(-1)、275.9 g?d~(-1)?只~(-1)、317.6 g?d~(-1)?只~(-1)和327.0 g?d~(-1)?只~(-1),夏季最低。TN、P、Cu、Zn的排泄系数分别为2.13 g?d~(-1)?只~(-1)、2.48g?d~(-1)?只~(-1)、2.56 mg?d~(-1)?只~(-1)、21.10 mg?d~(-1)?只~(-1);春冬两季的TN日排泄量显著高于夏秋两季; P的日排泄量表现为冬季极显著高于其余3个季节;夏季Cu的日排泄量与春季差异不显著,极显著低于秋、冬两季(P0.01)。TN在秋季排泄占比最低,春季最高;而P排泄占比为秋季最高,春季最低。肉鸭在饲养期TN、P、Cu、Zn的排泄量与对应元素的摄入量具有极显著的正相关关系(P0.01)。研究表明:季节因素能对肉鸭粪便中含水率、有机质、TN、P、Cu和Zn含量产生显著影响,同时各季节各元素的排泄量与相应元素的摄入量显著相关。     

排水沟塘分布特性及与农田水力联系对水质净化能力的影响

湿地是一种能够有效治理农业非点源污染的生态设施;在一些无法建设人工湿地的地区,现存的排水沟塘系统具有类似湿地的水质净化效果。为研究排水沟塘的分布以及其与农田水力联系对其水质净化能力的影响,该文以扬州市江都区昭关灌区为例,首先通过实地调查,明确研究区不同形式沟塘的分布规律,确定沟塘与农田逐级详细水力联系,然后建立理论分析模型,分别计算考虑与不考虑水力联系2种情况下,沟塘的污染物去除能力。结果表明,考虑水力联系后,污染物去除能力为不考虑水力联系的70%~84%;水质净化作用主要集中在一些面积较大的支沟和池塘。从农田排水的角度考虑,尺寸较大沟塘会出现一定的水力冗余,但是从水质改善的角度看,则有必要保留。研究区可通过较为简单的工程措施来优化水力联系,提高其污染物的去除能力。     

The distribution of three uncommon freshwater gastropods in the drainage ditches of British grazing marshes

Marshland drainage channels (=ditches) in the UK are relicts of a once extensive habitat whose management requires quantitative information on the ecology of marshland organisms. Three freshwater gastropods in the UK Red Data Book (RDB), Segmentina nitida, Anisus vorticulus and Valvata macrostoma, are particularly poorly known, and we examined their macro-distribution across 106 ditches on four grazing marshes in SE England. Distribution reflected natural water quality, vegetation and anthropogenic factors. S. nitida occupied shallow calcareous ditches with dense emergent vegetation while A. vorticulus occupied less calcareous ditches with high plant diversity. Ditches with V. macrostoma were dominated by floating plants and slightly elevated chloride. S. nitida and V. macrostoma were absent from otherwise suitable ditches that had elevated nitrate and nitrite indicating effects from eutrophication. Conservation of these three gastropods at the regional scale requires reductions in catchment fertiliser use and also the protection of enough sites to provide the required range of natural factors (e.g., Cl and Ca). At the marsh scale, we suggest that quasi-traditional and rotational ditch clearance can provide the vegetation dynamics and diverse ditch network to ensure suitable habitat for all three species. Better information is required about dispersal, about the effectiveness of reintroduction, and about the most sensitive methods of ditch management.     

Effects of Composted Pulp and Paper Industry Wastewater Treatment Residuals on Soil Properties And Cereal Yield

The aim of this study was to investigate effects of pulp and paper industry wastewater treatment sludge composts on soil and cereal crops. Five forest industry wastewater sludge composts were tested in a field study which was conducted in a silty clay soil in southern Finland with barley in 1998, with oats in 1999 and with barley in 2000. Two composts contained only pulp mill biosludge and bark in a ratio of 1:4 and 1:2, respectively. Two other composts were mixtures of biosludge and primary sludge with the addition of bark in a ratio of 1:2 and 3:4, respectively. These two wastewater sludges originated from a pulp mill and from a recycled paper mill. The fifth compost consisted of biosludge and primary sludge from a board mill. Two application rates of each compost were studied: the low rate was based on an annual P fertilization rate recommended for barley, 50-200 m³/ha; and the high rate was a double or triple the low rate depending on the mineral N concentration of the compost, 150-600 m³/ha. Based on the Finnish fertilizer recommendations, nutrient demands of the test plants were annually fulfilled by mineral fertilizers depending on the treatment. Total contents of N, P, K and Ca in composts were 8.8-17.5, 0.7-3.9, 1.5-6.5, and 4-25 g/kg dry matter, respectively. Especially at high doses, composts had beneficial effects on soil bulk density, porosity, C and N contents and C:N ratio. Despite the high total N rates applied with the composts, the mineralization following crop harvest did not significantly increase soil nitrate late autumn or following spring as compared to the soils that received mineral fertilization. There was no significant difference in the grain yields between plots that received mineral fertilization and compost treatments supplemented with mineral fertilizers. However, there was a decreased fertilization effect of some composts on straw yields during the first experimental year, indicating immobilization of mineral N. Heavy metals added in soil with the composts did not significantly increase their concentrations in the grain crops. All the composts had relatively low nutrient contents and low fertilizing value, but beneficial effects on soil properties and were regarded as soil conditioners. Soil improving and fertilizing effects of the composts varied annually depending on the weather conditions during the growing season. Heavy metal concentrations of the composts studied were far below the limit values set for the soil conditioners in the Finnish government regulations.     

Changes in Acetoclastic Methanogenic Activity and Microbial Composition in an Upflow Anaerobic Filter

Changes in the acetoclastic methanogenic activity in the effluentfrom an upflow anaerobic filter (UFAF) were studied throughout a 36 week operating period. The UFAF formed the second phase of a two-phase laboratory-scale anaerobic treatment system. TheSpecific Methanogenic Activity (SMA) test was used to measurethe acetoclastic methanogenic activity of the biomass washed outfrom the UFAF. Throughout the operating period, the SMA testswere carried out at different organic loading rates (OLR) up to6.7 kg COD m^-3 d^-1 and upflow velocities (UV), 5 m d^-1 and 15 m d^-1. The results showed that thebiomass washed out from the UFAF consisted of up to 55%(considered as a draft value) acetoclastic methanogens producing550 mI CH₄ g^-1 VSS d^-1. This high acetoclasticmethanogenic activity measured in the effluent might have beendue to the existence of Methanosaeta (formerly Methanothrix) species. Towards the end of operation,Epifluorescence Microscopic examinations in the effluent revealedthat Methanococcus species were the most dominant groupfollowed by medium rods and short rods, filaments and long rodsand the least dominant Methanosarcina species. Theperformance of the UFAF was not adversely affected by the loss ofthe active biomass and changes in their composition. The UFAFsystem achieved over 85% COD removal efficiency at thehighest OLR of 6.7 kg COD m^-3 d^-1 and UV of 15 m d^-1. Throughout most of the operation, methane yield rangedfrom 0.28–035 m³ CH₄ kg^-1 COD_removed.     

NUTRITION OF CONTAINER-GROWN CHRISTMAS CACTI

The effect of nitrogen (N), phosphorus (P), potassium (K) and lime additions to container-grown Schlumbergera x buckleyi were examined in two experiments. In each case rooted cuttings were grown in peat/perlite (1:1, v/v), with three plants per pot, for 17 months in a heated greenhouse. Foliage growth and flowering were strongly enhanced by added N and fertilization of between 1800 and 2200 g N m^{? 3} (105–130 g N m^{? 3} per month) and a foliar N content of 3.4–4.2% were recommended. Flowering was delayed by high N but promoted by added P. Added P also strongly influenced foliage growth and flowering but at lower rates than that for N fertilization. Recommended P rates were between 650 and 850 g P m^{? 3} (40–50 g P m^{? 3} per month) and a foliar P content of 1.3–1.5%. This species appeared tolerant of a wide range of pH levels, with a range of lime rates having no significant effect. A foliar calcium (Ca) content of 0.7% to 0.9% was suggested with a recommended media pH of 5.5–6.5. High K strongly influenced the production of stem segments and flowering in a small experiment and fertilization of 1500–2000 g K m^{? 3} (90–120 g K m^{? 3} per month) and a foliar content of 1.8–2.6% K were tentatively recommended.     

Limestone liners to protect groundwater quality against organic wastewater seepage

Crushed limestone was tested as a sealing liner for organic wastewater storage facilities. This material was compacted in laboratory columns and exposed in quadruplet to three levels of wastewater total solids (TS of 0.6, 1.3 and 2.6%). A fourth set of quadruple columns was used to monitor the total nitrogen (TN) loading rate using 1.3% TS wastewater. The crushed limestone cores measured 310 mm in depth by 98 mm in diameter and were exposed to a typical wastewater depth of 290 mm. Wastewater TS and ambient temperatures had a marked effect on seepage and TN loading rates. If the wastewater contains at least 1.3% TS, the seepage and N loading rate can be limited to 2 × 10^-8 m s^-1 and 200 mgN m^-2 d^-1, respectively. Ambient temperatures below 5 °C caused the TN loading rate to increase 7 fold, while those above 5 °C favoured nitrifying and denitrifying activity, thereby reducing seepage TN.     

Evaluation of the Fate of Ciprofloxacin and Amoxicillin in Domestic Wastewater

The main objective of this study was to evaluate the contribution of sorption to the removal of two commonly used antibiotics (amoxicillin and ciprofloxacin) from wastewater. These antibiotics are excreted in large quantities with more than 75% of them being unmetabolized and are therefore likely to end up in domestic wastewater in significant quantities. The specific objectives were to determine the sorption behavior in synthetic wastewater (SWW), the effect of pH and contribution of microbial surfaces, to the sorption of these antibiotics. The SWW, adjusted to various pH levels, was used and sorption kinetics conducted at 100 and 250 ??g L^?1 concentrations. Adsorption isotherms were determined at different pH levels. The SWW (pH 6.6) was inoculated with Rhodococcus sp. B30 strain to determine the contribution of microbial surfaces to sorption. Generally, both antibiotics revealed a decrease in sorption with pH increase, suggesting that lowering the solution pH of the wastewater may reduce their amounts in wastewater solution. Comparatively, ciprofloxacin exhibited higher sorption than amoxicillin. The sorption distribution coefficient (K _d) values for ciprofloxacin ranged from 0.4356 to 0.8902 L?g^?1, with pH?=?5.5 exhibiting the highest K _d, while that for amoxicillin ranged from 0.1582 to 0.3858 L?g^?1 with the highest K _d at pH?=?3.5. There was a significant difference (p?<?0.05) in K _d values between various pH levels for both antibiotics except between the pH of 5.5 and 6.6. Both antibiotics were not degraded within 48 h by Rhodococcus sp. B30 strain. These results indicate that degradation may not be the major process of removal of compounds from wastewater treatment plants and hence the importance of sorption as an intervention technique.