Hanna Obarska-Pempkowiak

Potential fertilizing properties of sewage sludge treated in the sludge treatment reed beds (STRB)

In previous research the fertilizer value of sludge from reed beds was evaluated based on the sampling sludge on different depths from four Danish sludge treatment reed beds (STRB) after long periods of stabilization. The dewatering efficiency of sewage sludge in the STRB is comparable to mechanical dewatering. The long-term stabilization of sewage sludge progressively decreases the concentration of organic matter due to the process of humification. The aim of the work was to determine the changes of organic matter concentration, nutrients concentrations as well as speciation of selected heavy metals (Cd, Pb, Ni, Cr, Cu and Zn) in vertical profile of the sewage sludge stabilized in the STRB for 7-15 years. The analyzed sewage sludge was collected from the STRB treating sludge from four municipal wastewater treatment plants located in Denmark serving from 9,000 to 40,000 person equivalent. Analyzed heavy metals (except for Zn) were mostly bound with the most stable - residual - fraction. The most stable metals were Pb and Cr, where the share of the residual fraction exceeded 80.0%. The most mobile metal was Zn, where the share of the mobile fractions (calculated as the sum of I, II and III fractions) exceeded 85.0%. The high concentration of nitrogen and phosphorus is the decisive factor in the high valuation of sludge stabilized in the STRB as fertilizer.

Domestic Wastewater Treatment

SSF systems are usually applied at the 2nd stage of domestic wastewater treatment, after mechanical treatment. The number of such installations working at the moment in Europe is estimated to be 100,000. In Germany about 10,000 systems are in operation.

Experiences of Salix viminalis application to water and sewage treatment

Willow (Salix), a pioneer plant in land reclamation process, was taken into account when a conception of plantations watered with sewage was developed. New application of Salix is an energy source. The experiences show that willow buffer zones can be used for removal of pollutants from diffuse sources. Laboratory and field experiments proved that Salix viminalis can be applied for treatment of sewage in individual household treatment plants. Application of willow gives increase of treatment efficiency in comparison to soil filters. Studies also show a successful application of willow plantations for sewage sludge utilization.

Application, design and operation of constructed wetland systems: case studies of systems in the Gdansk region, Poland

Abstract Constructed wetland systems in Poland are applied to provide secondary treatment of domestic wastewater, protection of surface water and treatment of landfill leachate. Due to climatic conditions vegetated submerged beds (VSB) are most commonly applied for sewage and leachate treatment. For water protection systems with FWS or with mixed flow are more commonly used. The objective of the study was to recognize the efficiency and operation conditions of existing constructed wetland in Poland. It was concluded that discharging of too high loads of contaminations as well as too high hydraulic loadings leads to beds clogging and to the decrease of treatment efficiency in consequence. The average rates of organic matter and total nitrogen decomposition rates at the CW Wiklino were twice higher for the HF-CW II in comparison to corresponding rates for HF-CW I. The constants were dependent not only on temperature of sewage but on loads of contamination in the sewage as well.

PRE-FEASIBILITY STUDY FOR TREATMENT WETLAND APPLICATION FOR WASTEWATER TREATMENT IN DISPERSED DEVELOPMENT

The aim of the paper is to present the conducted analyses of pre-feasibility study of different approaches for wastewater management in a settlement of 180 persons. In the assessment both technical and economic aspects were analyzed. The costs were calculated for three different and, at the same time, most popular as well as possible technical solutions like: (i) construction of local wastewater treatment plant with gravitational and pressurized networks, (ii) construction of single family wastewater treatment plants, (iii) construction of sealed septic tanks. Carried out analyses of investment and maintenance costs revealed that at the stage of construction the most expensive is local sewer network with treatment plant, while the construction of a single family treatment plant has similar cost regardless of the technology used. When the long term operation and investment cost are accounted the most economical reasonable solution is the application of wetland treatment for household wastewater treatment.

Treatment Wetlands in Rural Areas of Poland for Baltic Sea Protection

Water and wastewater management, especially in rural areas, greatly affects loads of nutrients discharged to the Baltic Sea. In Poland, this management is unbalanced because of the dispersed development and in many locations construction of sewerage system is uneconomic or even impossible. For this reason, a significant part of sewage from single-family houses in rural areas must be discharged into domestic sewage systems. The aim of this paper was to analyze the data concerning the Baltic Sea catchment area as well as to present some current results of research on wastewater management mainly in rural areas. Small on-site wastewater treatment plants are usually defined as facilities serving up to 50 people. Depending on the law, their maximum capacity is set at 5 m3 d−1 (according to the Polish Act of Water Law). In rural areas, treatment wetlands seem to be especially useful as on-site wastewater treatment plants. The study indicates the high efficiency of pollutants removal in treatment wetlands, namely, hybrid treatment wetlands with at least two stages of treatment. High treatment efficiency is very important for the protection of the Baltic Sea. The reliability assessment based on Weibull distributions allows for the risk assessment of exceeding the limit values of pollutants in treated wastewater. Very good reliability was observed for TN and COD (303 and 292 day per year, respectively), while reliability for BOD5 and TSS was weaker (219 and 153 day per year, respectively). Proper design and operation of treatment wetland facilities are important in order to achieve a good quality of effluent in the interests of Baltic Sea protection.

Operational problems of constructed wetland for landfill leachate treatment: case study

The present paper discusses the quality fluctuations of leachate from municipal land fill in Gdansk (Poland) over the last 5 years and the evaluation of a wetland system de signed for treatment of the leachate. The research has been conducted during a 5-year period. The constructed wetland for leachate treatment was built in 2001; it consists of 2 horizontal subsurface flow reed beds, working in parallel. In the period 2005–2006 it underwent modernization due to unsatisfactory treatment results caused by bed clogging. After the modernization the treatment effectiveness is satisfactory. The effluent from bed I met Polish outflow standards, while in the effluent from bed II COD, total N and TSS exceeded the required concentrations. In spite of this, pre-treatment of leachate (iron removal) should be quickly introduced to protect the system against the reoccurrence of clogging problems.

Sludge Treatment Reed Beds (STRBs) as a Eco-solution of Sludge Utilization for Local Wastewater Treatment Plants

Sewage sludge is a by-product of wastewater treatment processes. In Poland, the amout of sewage sludge has been still growing in recent years, due to inhencement of pollutants removal in wastewater treatment plants (WWTPs). One of the systems used to transform sewage sludge into fertilizer is a technology called Sludge Treatment Reed Beds (STRBs). Reed systems are periodically irrigated with sewage sludge with a low dry matter content (from 0.5 to 1.5 % DM). The accumulation time of sludge necessary to achieve stabilization is approximately 10–15 years. Sludge is transformed into humus substances. After checking the microbiological and physico-chemical properties stabilized sludge can be used for agricultural purposes. In the recent years, Denmark, France and Germany have applied integrated technologies of dewatering and stabilization of sewage sludge in these systems. The aim of the study is to present: (i) general principles for the construction and for the design of reed systems for integrated dewatering and stabilization of sewage sludge, (ii) conditions of proper operation of the systems (iii) the economic and environmental aspects of using reed technology based on the literature and our own research. Conducted research confirmed that sewage sludge dewatered and stabilized in STRBs can be used as fertilizer in agriculture.

Dewatering of Sewage Sludge Dewatering in Reed Systems

Within the last several years new methods of sewage sludge utilisation have been introduced.

Types of Treatment Wetlands

The removal of pollutants in treatment wetland systems is the result of the sorption of biochemical pollutants, redox reactions, and a biological activity of microorganisms as well as hydrophytes plants.