Posted: June 8th, 2015

An Evaluation of Modified Pervious Pavement for Water Harvesting

2.1 The Concept of Sustainable Urban Drainage (SUDs)

Sustainable urban drainage systems (SUDS) are approaches that are natural and are used to manage waste in and around properties and other developments. It slows and holds back water that runs off from a site. It, therefore, allows pollutants to be broken down. There are many types of SUDs. There are site control measures that manage surface water run-off such an as roads and business park. There are source control measures that lead run-off close to where the water lands. There is also regional control measure.

 

USD techniques are recommended, and they are used in many parts of the world. Its terminologies vary in different parts of the world. Multiple aspects of engineering and economics should be taken into account when applying the concept of sustainable water management in urban areas. SUDS components can be integrated with traditional conveyance systems to satisfy both quality and quantity needs of flood management.

 

Urban drainage has played many different roles in cities. The primary aim of urban drainage is providing a mechanism that is convenient for waste cleaning for public hygiene and for an efficient conveyance facility to protect flood. In the past years, additional attention has been on environmental protection and the recreational benefits of urban drainage. (Qianqian Zhou, 2014)

 

Various urban drainage designs were created due to the need to manage these fluids. A different sanitary sewer system is designed to carry only wastewater to the treatment plant while the storm is taken on a separate system. It is not transported to the treatment plant but disposed of separately. However, in a combined sewer system, both wastewater and stormwater are carried in the same set of pipes. There are continued debate among researchers, drainage engineers and regulatory agencies on the best system of conveyance of storm water in relation to quantity and treatment costs (Butler and Davies, 2000; EPA, 2000b; DEG, 2001; Suarez and Puertas, 2005; Schultze and Rhode, 2005), with the pro-combined system lobby claiming that at least all storm water passes through a treatment plant prior to discharge and the separate system lobby pointing, for example to storm water overflows (SWOs).

 

Some connected components should be considered when designing a suitable drainage system. One can include source control measures to capture and treat runoff close to where it lands. Source control can be connected to site control measure. The overflow from site control measures can be finally dealt with in a regional control SUDS measure before it’s finally discharged into the water environment.

 

The design of urban drainage systems has been driven at different time periods by different objectives and influenced by various aspects. They include climate, topography, geology, engineering and construction capabilities, scientific knowledge, societal values, and religious beliefs (Burian and Edwards, 2002). Ancient civilizations accounts (e.g., Indus and Minoan) indicate that drainage systems were carefully made with trial and error construction methods. It helped achieve the main aims of rainwater collection, prevention of flooding and waste removal (Kirby et al., 1956; Mumford, 1961; Webster, 1962; Burian and Edwards, 2002).

 

The amount of pollutants carried into waters is increased by urbanization. In an urban area, the land surface is majorly covered by many buildings, pavement and landscapes that have drainage that is impaired. Pollutants as a result of urban water runoff include; grease dirt from the rooftops and even heavy toxic metals.

 

2.2 The impact of low impact development
When conventional drainage systems linked tourbanization replaces the open land with impervious surfaces, water balance is altered, and this encourages pollution runoff at the detriment of filtration. Low impact development concept started in 1990 in Maryland as an alternative to the traditional BestManagement practices in controlling stormwater and maintaining predevelopment hydrological characteristics of the urban catchments.

 

2.3 Uses of pervious pavements in urban drainage.

Pervious pavement systems (also referred to as permeable or porous pavement systems) are important part of the Sustainable Drainage System (SUDS) approach to urban drainage (Newman et al., 2004b; Collins et al., 2006). Pavements in car parks and driveways have the potential to eliminate discharge and the runoff volume that flows into urban drains and improve runoff water quality. Water quality is improved by trapping the sediments in the infiltrated water.

 

There two types of pervious pavement surfaces, that is, C&M Ecotrihex pavers and also Atlantis tuff. Their performance is compared against a conventional asphalt paved car park. Permeable pavements can be introduced as a sustainable urban stormwater management feature (Jayasuriya and N. Kadurupokune, 2008)

 

Pervious pavements are divided into permeable and porous pavement. If a car park is built with both types of pervious surfaces the permeable and porous and an impervious asphalt surface used as a control, each pavement type will form actually isolated ‘catchments’ that are separated from each other and also from the surrounding landscape. It helps to avoid runoff ‘contamination’ of the individual test site. Lateral water flow will be mitigated by a sub-surface geo-membrane structure. Stormwater will flow through the pervious surface and subsurface media and be drained to the outlet via a geo-sock protected perforated header pipe.

 

About 5 years ago, over 500,000m2 of permeable pavements were built in the United Kingdom alone (Newman et al., 2004b) and about 30% of these installed pervious pavement were under sealed, thus having potential of being used as a stormwater storage device (Newman et al., 2994b).Hence, it would be logical to use the water storage capacity of the previous pavements system instead of using separate water tanks in places where the installation is accurate (Couple and Nnadi, 2007). The pervious pavement system is capable of removing stormwater pollution especially hydrocarbons through biodegradation filtration and sorption(Pratt, 1995; Bond, 1999; Coupe et al., 1999; Pratt et al., 1999; Coupe 2000, Newman et al., 2002a,b; Newman et al., 2002c; Brattebo and Booth, 2004; Newman et al., 2006a.b). Hence, permeable pavements provide a solution to urban drainage problems as well as downstream aquifer pollution especially with increased use of cars (Brattebo and Booth, 2004).

 

2.4 A Brief Review of Completed Ph.D. Work in Porous Pavement Research Group

Berry (1995) laid the foundation of Ph.D. research on the porous pavement in Coventry University. Her work determined the structure of laboratory PPs models. She tested the suitability of the blast furnace slag, granite, limestone as sub-base materials for the construction of the porous pavement system and established that granite is the best building material for the sub base of the support of the PPs. Granite was shown to have good load bearing capability as well as best water holding quality within the void ratio of the granite pieces. Her work also established the need for a geotextile within the porous pavement system and the effectiveness of Terram 1000® (Terram, Ltd UK) polypropylene geotextile in retaining pollutants and improving and water quality. Berry’s work created an understanding of the geological and hydrological properties of porous pavement systems. Her design of a rainfall simulator which she used for testing infiltration and water holding capability of the porous pavement models paved the way for the use of rainfall simulator on porous pavement types and established the potential of system as a source control system for urban drainage.

 

Coupe (2004), Studied the structure and characteristics of the oil-degrading microbes within the porous pavement system using scanning and transmission electron microscopy. He looked at the microbial diversity within the system and studied the effects of fungi and protozoa on the biodegradation process. He successfully identified some of the consumers of the primary decomposers such as Protozoa, testate amoeba, micro flagellates, gymnamoeba, ciliates and even metazoans including nematodes and rotifers. Coupe’s work showed that the protozoan diversity came from some of the components of the PPs especially the granite sub-base material. His work showed the importance of the protozoan community in the biodegradation process within the pervious pavement system. He demonstrated this by removing the prokaryotic community by dilution, filtration and anti- microbial agents that resulted in a reduction in the biodegradation rate within the PPS. He compared recycled concrete end granite as sub-base materials. He observed that granite supported a more complex protozoan community than concrete; while concrete supported more metazoans. On analysis of effluent after oil addition, he also discovered that concrete sub-base system retained more oil than granite system. Coupe, (2004) also did a preliminary analysis of effluent from field based PPS for water quality. His work raised up a lot of side issues for further research. However, he was the first researcher to identify other microbial communities apart from bacteria within the PPS and their importance in the biodegradation process.

 

Chapter 3: Water Quality of Waters Derived From a Range of Pervious Pavement Systems

3.1 Introduction

There is no doubt that urban run-off is often polluted with contaminants. The type and level of pollutant present in a particular run-off is dependent on the environment, the speed of flow, etc., (Dechesne et al., 2004; Eriksson et al., 2007). However, the common stormwater pollutants are hydrocarbons, metal, dust, microbes, pesticides and herbicides (Park and Stendtrom, 2005; Weiss et al., 2007; Coupe et al., 2006a). Also, research on the microbiological component of stormwater pollution is presented in chapter six. The pervious paving system has been shown to possess the capability to remove pollutants from stormwater through attenuation and biodegradation in situ.

 

3.11 Irrigation Water Quality Standard

It is obvious that some water treated and stored in pervious pavement system has to meet various quality standards to be considered for reuse as credible irrigation water. These rules will differ from the standards applicable to both simple disposals to a watercourse and for drinking water use. Various parameters are used to determine the quality of irrigation water. They include;

Electric Conductivity (Tarchitzky et al., 2007)

Ph (Tarchitzky et al., 2007; Heidarpour et al., 2007)

Total dissolved solids (TDS) (Tarchitzky et al. 2007)

Total oil or /mineral oil in water (Tarchitzky et al., 2007

 

6.1 CHAPTER 6: BIOLOGICAL WATER SAFETY OF RECYCLED WATER IN PERVIOUS PAVEMENTS SYSTEM.

6.1 Introduction

The sustainable drainage system is a way of improving how stormwater is managed, particularly within urban areas. The use of SUDS is now recognized as good drainage practice in the UK, featuring in recent legislation and changes to building standards. As SUDS become the mainstream, there will be an increasing need to improve the performance and offer multiple benefits to the end user. Moving beyond drainage design, SUDS can be linked to renewable energy schemes to provide value engineered solutions and contribute much to the overall sustainability rating of a site (Coupe et al., 2008).

One of the most obvious ways that SUDS can provide the benefit other than drainage or water quality improvements is in rainwater harvesting, which can significantly reduce the demand for primary water.

 

6.1.1 Pathogenic Organism in Harvested Water and Health Effects

Potentially there are some possible contaminating microbial types in harvested rainwater, of different taxonomic descriptions (Evans et al., 2006; Grabiowiecki et al., 2008) and which may increase in number under a variety of different conditions. Since there was no definitive data on the microbiological safety of rainwater harvesting systems, many collection systems have a micro filter that would remove most bacteria and protists from the system. Such filter systems are relatively susceptible to faults such as blockages if a large amount of suspended material is found in the water, for example after intense rainfall.

Most human microbial pathogens found in water recycling application are enteric in nature and enter into the environment through fecal and sewage contamination as runoff from agricultural soil and livestock manures (Toze, 2006). These organisms include bacteria, protozoa, helminthes, and viruses. The potential health hazards that may arise from this practice could be enormous as contamination of agricultural products may result if the water was no well treated to remove potential pathogenic microbes. The potential pathogenic waterborne micro-organisms can be divided into four main groups: bacteria, protozoa, viruses, and helminthes. These groups are discussed below.

 

6.1.1.1 Bacteria

Bacterial pathogens and opportunistic pathogens can be found in wastewaters and harvested waters. Most potentially pathogenic bacteria are enteric in nature, but non-enteric pathogenic bacteria such as Legionella ssp., Mycobacterium spp., and Leptospira have also been found in wastewater and are capable of self-replication (Toze, 2006)

 

6.1.1.2 Protozoa

Protozoa are a diverse and abundant group of microorganisms that feed by engulfing other organisms. They live in a broad range of habitats including aquatic environment and are divided into four major groups: flagellates, naked amoeba, testate amoebae and ciliates (Arnott, 2001). Protozoa have long been used as indicators of water quality (Finlay, 1997).

6.1.1.3 Viruses

Enteric viruses are the smallest single-stranded RNA pathogens found in water ranging from 20nm to 30nm in diameter (Fong and Lipp, 2005; Toze, 2006). They usually occur in water through the contamination of water with sewage/fecal matter (Bosch, 1998; Fong and Lipp, 2005; Toz, 2006), urban runoff and wastage discharge (Fong and Lipp, 2005). High levels of persistent enteric viruses in marine environment for recreational activities and infection of shellfish which tends to build up these viruses in their tissues more then it may even bar found in surrounding water environment (Lees et al., 1995; Myrmel et al., 2004; Fong and Lipp, 2005).

 

6.1.1.4 Helminthes

Helminthes are parasitic worms that might constitute a health risk if founding in recycling water applications. They can be seen with naked eyes when mature. They produce eggs for reproduction. Waterborne Zoonic helminthes are mostly opportunistic parasites that are transmitted from animals-man and vice-versa through the fecal-oral route.( Nithiuthai et al., 2004).

6.1.3 Aim

The experiment’s principal aim presented in this chapter was to determine some aspects of the level of water quality that the pervious pavement system has the potential of storing within the system in view of the threat that some potential pathogens (such as Escherichia coli and Acanthamoeba spp.) poses in stormwater recycling application and storage.

This study also intends to determine the fate and persistence of this potentially pathogenic protist(Acanthamoeba polyphaga) in the previous pavement system as the organism interacts with the indigenous microbial community in the system.