Sludge drying reed beds: A key ecotechnology for a sustainable sanitation infrastructure in Brazil

Os lodos de esgotos tornaram-se uma importante questão na gestão das cidades devido ao enorme volume produzido diariamente, ao potencial de impacto ambiental e social deste produto e ao fato de seu gerenciamento e disposição serem um dos processos mais complexos em estações de tratamento de esgotos. Os objetivos deste estudo foram avaliar a eficiência de filtros plantados com macrófitas no tratamento de lodo de tanque séptico e monitorar o processo de desaguamento e mineralização do lodo acumulado no leito do filtro. O sistema foi operado semanalmente com taxa de 125 kgST/m².ano e tempo de detenção hidráulica de 6 dias. O filtro apresentou eficiências de 95, 99, 87 e 95% para os parâmetros ST, DQOt, N-NH4+ e P-PO43-, respectivamente. O lodo acumulado apresentou a maior concentração de ST (49%), 83 dias após o último ciclo de alimentação do filtro. A concentração média de ST do lodo acumulado permitiu classificá-lo como sólido duro. Palavras-chave: lodo de tanque séptico; filtros plantados com macrófitas; tratamento de lodo séptico; biossólidos. Use of Sludge Drying Reed Beds for Dewatering and Mineralization of Sludge from Septic Tank ABSTRACT The sewage sludge has become an important issue in the management of cities due to the volume produced daily, the potential environmental and social impact of this product and the fact that its management and disposition to be one of the most complex processes in sewage treatment plants. The objectives of this study were to evaluate the efficiency of sludge drying reed beds in the treatment of septic tank sludge and monitor the process of dewatering and mineralization of the residual sludge. The system was operated weekly, with rate of 125 kgST/m².year and hydraulic retention time of 6 days. The filter presented efficiencies of 95, 99, 87 and 95% for parameters TS, COD, N-NH4+ e P-PO43-, respectively. Residual sludge had the highest concentration of TS (49%), 83 days after the last cycle the filter. The average concentration of TS presented the residual sludge allowed to classify it as a solid hard. Keywords: septic tank sludge; sludge drying reed beds; treatment of septic sludge; biosolids.

Download Full-text

Sludge drying reed beds: full- and pilot-scale study for activated sludge treatment

Water Science & Technology ◽

10.2166/wst.2009.388 ◽

2009 ◽

Vol 60 (5) ◽

pp. 1145-1154 ◽

Cited By ~ 13

Author(s):

S. Troesch ◽

A. Liénard ◽

P. Molle ◽

G. Merlin ◽

D. Esser

Keyword(s):

Dry Matter ◽

Loading Rate ◽

Rest Period ◽

Matter Content ◽

Full Scale ◽

Dry Matter Content ◽

Loading Frequency ◽

Reed Beds ◽

Hydraulic Behaviour ◽

Sludge Drying

Sludge drying reed beds have been used for dewatering and mineralization of sludge since the beginning of the 90s, but their insufficient performances in terms of Dry Matter [DM] content and mineralization of the sludge have made necessary new studies. Therefore, 8 pilots of 2 m2 each and a full-scale plant (13,000 p.e, 8 beds of 470 m2 in operation for 4 years) have been monitored to examine the influence of the sludge loading rate, the sludge quality and the loading frequency on the dewatering and mineralization efficiencies. Two filtration layers and two loading rhythms were tested on pilots which were fed at a loading rate of 25–30 kg DM m−2 yr−1 during the first year of operation (commissioning period). Hydraulic behaviour (infiltration rate, outflow), O2 and CO2 relative concentrations in the filtration media, redox potential, pollutants removal and dry matter content were assessed during all the study. The rheological quality of the extracted sludge from full scale beds was assessed and showed that its mechanical behaviour exceed those of sludge of comparable dry matter content, making its spreading easier. Therefore, this sludge could easily claim the status of solid and stabilized sludge according to the French regulation. Design and management recommendations (number of beds, loading rates, feeding/rest period) gained from the experiments results are suggested.

Download Full-text

Characteristics of Sludge Moisture Content Variation in Sludge Drying Reed Beds

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.768.515 ◽

2015 ◽

Vol 768 ◽

pp. 515-519

Author(s):

Xin Nan Deng ◽

Yu Bo Cui ◽

Wei Gao ◽

Rui Chen

Keyword(s):

Moisture Content ◽

Pilot Scale ◽

Coarse Sand ◽

Reed Beds ◽

Conventional Drying ◽

The Media ◽

The Difference ◽

Reed Bed ◽

Sludge Drying ◽

Media Layer

Sludge moisture content was investigated at different stages during the test. Pilot-scale sludge drying bed and sludge drying reed beds had the same size of 3 m×1 m×1.3 m, and the bed height consisted of a 65 cm media layer and a 65 cm extra height. The media layer is filled with slag (20 cm), gravel (20 cm), coarse sand (5 cm) and quartz sand (24.5 cm) from the bottom in turn. Unit 1 was a conventional sludge drying bed, unit 2 was a sludge drying reed bed. Unit 1 and unit 2 had ventilation pipes which were mounted on the drainage pipes. Unit 3 was a sludge drying reed bed without ventilation pipe. The waste activated sludge was feed into the three units periodically during the experiment. The experiment investigated the sludge moisture content. At the end of the operation, the sludge moisture content in three units decreased by 18.52%, 22.37%, and 20.68%, respectively. It was found that the dewatering effect of the sludge drying reed bed was better than the conventional drying bed. The effect of plant growth on sludge dewatering is greater than the ventilation, but the difference was not significant.

Download Full-text

Sludge drying reed beds for septage treatment: Towards design and operation recommendations

Bioresource Technology ◽

10.1016/j.biortech.2011.06.019 ◽

2011 ◽

Vol 102 (17) ◽

pp. 8327-8330 ◽

Cited By ~ 26

Author(s):

J. Vincent ◽

P. Molle ◽

C. Wisniewski ◽

A. Liénard

Keyword(s):

Reed Beds ◽

Sludge Drying

Download Full-text

Greenhouse gas emissions from sludge treatment reed beds

Water Science & Technology ◽

10.2166/wst.2015.018 ◽

2015 ◽

Vol 71 (7) ◽

pp. 1011-1018 ◽

Cited By ~ 5

Author(s):

Yubo Cui ◽

Shunli Zhang ◽

Zhaobo Chen ◽

Rui Chen ◽

Xinnan Deng

Keyword(s):

Co2 Emission ◽

Ch4 Emission ◽

Gas Emission ◽

Sludge Treatment ◽

Reed Beds ◽

Volatile Solids ◽

Gas Fluxes ◽

Reed Bed ◽

Sludge Drying ◽

Transparent Chamber

Sludge treatment reed bed systems (STRBs) are considered as an alternative technology for surplus sludge treatment. Organic matter is decomposed by various microbial reactions, resulting in gases such as CO2 and CH4 emitting into the atmosphere. The aim of this study is to investigate gas emission from STRBs. The static transparent chamber was adopted to measure gas emission; it allows sunlight to enter and plants to photosynthesise. The comparison of total solids and volatile solids showed STRBs have a higher efficiency in dewatering and mineralization than a conventional unplanted sludge drying bed (USDB). The CO2 emission ranged from 28.68 to 100.42 g CO2 m−2 d−1 in USDB, from 16.48 to 65.18 g CO2 m−2 d−1 in STRBs; CH4 emission ranged from 0.26 to 0.99 g CH4 m−2 d−1 in USDB, from 0.43 to 1.95 g CH4 m−2 d−1 in STRBs. Both gas fluxes decreased towards the end of vegetation and reached the highest rates during the hot and dry summer. After the system was loaded by sludge, the fluxes of CO2 and CH4 significantly decreased in the USDB, whereas they increased in STRBs. In terms of CO2 equivalent, the global warming potential of CH4 was 13.13 g CO2eq m−2 d−1 and 15.02 g CO2eq m−2 d−1 in USDB and STRBs, respectively.

Download Full-text