摘要:

This work presents preliminary results from two constructed wetlands for municipal wastewater treatment in Estonia: (1) a free water surface constructed wetland (a cascade of 4 serpentine ponds in whichTypha latifoliaandPhragmites australishave been planted (total area about 1.2 ha, mean depth of the ponds 0,5 m) for secondary treatment of waste water from the town of Põltsamaa with about 5,000 inhabitants and from a food processing factory, and (2) a two‐chamber horizontal‐flow sand‐plant filter (two chambers, 30x6.25x1.0 m, each) filled with coarse sand, one planted withTypha latifolia,and the other withIris pseudacorusandPhragmites australis,receiving a septic tank effluent of about 40 population equivalents in Kodijärve. The horizontal flow sand‐plant filter showed satisfactory purification efficiency in terms of BOD7and phosphorus (66–95% and 63–96%, respectively). However, nitrogen removal was relatively low, varying from 12 to 85%. In the cascade of free water surface wetlands, the most critical parameter is phosphorus retention. Mean purification efficiency observed was about 73% for nitrogen, 68% for BOD7and 24% for phosphorus. Purification efficiency in both wetland systems did not decrease during the cold season.

ISSN:1093-4529    

DOI:10.1080/10934520009377042

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A technical reed bed treatment system (RBTS) with vertical‐flow (VF), which was filled with medium‐grain sand and planted with reed(Phragmites australis),was intermittently charged with domestic wastewater of 29 pe (population equivalents) at a surface flow rate of 23.3 L/m2‐d. At effluent temperatures of between 4.7 and 18.0°C, a COD (BOD5) mass loading rate of 11.7 (6.4) g/m2‐d sewage was degraded to effluent concentrations of <15–28 (<2–7) mg/L. Average COD (BOD5) elimination accounted for 94 (98) %. At effluent temperatures >6°C (April‐Dec), the applied mean nitrogen load of 1.9 g NH4+‐N/m2.d was nitrified to leave < 1.0 mg/L NH4+‐N in the effluent (mean influent concentration: 79.6 mg/L NH4‐N). Simultaneous denitrification in the VF removed 23% of the nitrogen input. Due to an unfavourable NH4+‐N/BOD5inlet ratio of 0.30 Nanorg., the removal rate only increased to 41% by recirculating effluent water into the inlet at a ratio of 1.1. Depending on the purification grade required, loading rates of 20–50 L/m2‐d and areas of 3–6 m2/pe are recommended for dimensioning VF.

ISSN:1093-4529    

DOI:10.1080/10934520009377043

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Detailed investigations have been conducted on a set of four pilot scale subsurface flow (SSF) constructed wetlands in order to characterise heat transfer, mass dispersion and biological performance mechanisms. These studies have followed the beds from post construction through unplanted hydraulic base line studies to the current status of mature stands ofPhragmites australis. Experimental observations indicate that in unplanted beds, daily thermal fluctuations are depth dependent and range from 1 to 9 degrees Celsius. These fluctuations result in daily thermal inversions, and enhanced mixing and oxygen transport. For planted beds, thermal fluctuations are depth independent, and have a constant amplitude of 2 degrees Celsius. Planted beds may be thermally stratified. Lithium tracer studies corroborate these results for the planted bed. In addition, performance studies indicate that organic pollutant removal is probably limited to organic suspended solids removal, with subsequent biological breakdown. Current first‐order plug flow models can not account for these operational issues. A combined model is necessary to account for lateral dispersion, temperature gradients and settling of suspended solids to accurately reflect real biological removal mechanisms.

ISSN:1093-4529    

DOI:10.1080/10934520009377044

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1093-4529    

DOI:10.1080/10934520009377045

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In East Germany a great amount of agricultural wastewater is derived from dairy farms. It is highly polluted with average concentrations of 3 300 mg/L COD and 460 000 Colony forming units (CFU)/mL fecal coliforms (FC). This study was designed to show how far constructed wetlands may eliminate pathogenic bacteria from dairy farm wastewater under changing climatic conditions. During both summer and winter a constructed wetland was loaded for 10 weeks with dairy farm wastewater with a hydraulic load of 0.013 m3/m2‐d and 0.010 m3/m2‐d, respectively. The removal rates for COD and FC were 89.2 and 99.3% in the summer and 92.0 and 95.8% in the winter, respectively. Survival and transport of FC in the water and the substratum are controlled primarily by temperature and type of substratum. Adsorption on soil particles plays a key role in the retention of FC.

ISSN:1093-4529    

DOI:10.1080/10934520009377046

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

To investigate if variations in concentrations occur at different levels within urine tanks and to evaluate possible consequences thereof, urine samples were collected from four collection tanks and one storage tank of different urine separating sewerage systems. Plant nutrients and metals were found to concentrate in the sediment at the bottom of the tanks. Also, densities of indicator bacteria were higher in the bottom layer, probably due to adsorption to sedimented particles. The differences in concentration at different levels became more apparent during storage of the urine mixture. After four months storage concentrations of the investigated indicator bacteria, except clostridia, were below detection limits at all levels. Considering the variability in nutrient concentration, samples from the middle level correspond well to the average composition in the tanks and can be used to calculate urine application rates. When estimating hygienic risks with the reuse of human urine the concentration variability also needs to be considered.

ISSN:1093-4529    

DOI:10.1080/10934520009377047

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Irrigation and fertilization of short‐rotation willow coppice with wastewater is a new way of reusing wastewater in Sweden. To evaluate the possible impact of viruses on groundwater quality, the transport and retention of the bacteriophageSalmonella Typhimuriumtype 28B were studied in two types of willow‐cropped field lysimeters containing clay or sand soil. Phages were applied to the soil surface and moderate irrigation was done daily under field‐like conditions.

ISSN:1093-4529    

DOI:10.1080/10934520009377048

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This investigation includes three years of full‐scale experiences at the first EBPR plant in Norway, Groos WWTP in Grimstad. The main focus was on low temperature performance (below 7 °C) and the effect of wastewater characteristics (COD). The treatment efficiency was not affected by low temperature; 0.35 mg/1 phosphorus in the effluent during 1998 (94 % removal). COD‐levels, however, did affect the process. The results from the study are used as a basis for retrofitting plants that removes phosphorus by chemical precipitation. Results from experiments at a partly retrofitted plant are also presented.

ISSN:1093-4529    

DOI:10.1080/10934520009377049

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:1093-4529    

DOI:10.1080/10934520009377031

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor